raylib/src/models.c

/*********************************************************************************************
*
*   raylib.models
*
*   Basic functions to draw 3d shapes and load/draw 3d models (.OBJ)
*
*   Copyright (c) 2013 Ramon Santamaria (Ray San - raysan@raysanweb.com)
*    
*   This software is provided "as-is", without any express or implied warranty. In no event 
*   will the authors be held liable for any damages arising from the use of this software.
*
*   Permission is granted to anyone to use this software for any purpose, including commercial 
*   applications, and to alter it and redistribute it freely, subject to the following restrictions:
*
*     1. The origin of this software must not be misrepresented; you must not claim that you 
*     wrote the original software. If you use this software in a product, an acknowledgment 
*     in the product documentation would be appreciated but is not required.
*
*     2. Altered source versions must be plainly marked as such, and must not be misrepresented
*     as being the original software.
*
*     3. This notice may not be removed or altered from any source distribution.
*
**********************************************************************************************/

#include "raylib.h"

#include <GL/gl.h>       // OpenGL functions
#include <stdio.h>       // Standard input/output functions, used to read model files data
#include <stdlib.h>      // Declares malloc() and free() for memory management
#include <math.h>        // Used for sin, cos, tan

#include "raymath.h"     // Required for data type Matrix and Matrix functions
#include "rlgl.h"        // raylib OpenGL abstraction layer to OpenGL 1.1, 3.3+ or ES2

//----------------------------------------------------------------------------------
// Defines and Macros
//----------------------------------------------------------------------------------
// Nop...

//----------------------------------------------------------------------------------
// Types and Structures Definition
//----------------------------------------------------------------------------------
// ...

//----------------------------------------------------------------------------------
// Global Variables Definition
//----------------------------------------------------------------------------------
// It's lonely here...

//----------------------------------------------------------------------------------
// Module specific Functions Declaration
//----------------------------------------------------------------------------------
static float GetHeightValue(Color pixel);

//----------------------------------------------------------------------------------
// Module Functions Definition
//----------------------------------------------------------------------------------

// Draw cube
// NOTE: Cube position is the center position
void DrawCube(Vector3 position, float width, float height, float lenght, Color color)
{
    float x = position.x;
    float y = position.y;
    float z = position.z;

    rlPushMatrix();

        // NOTE: Be careful! Function order matters (scale, translate, rotate)
        //rlScalef(2.0f, 2.0f, 2.0f);
        //rlTranslatef(0.0f, 0.0f, 0.0f);
        //rlRotatef(45, 0, 1, 0);
    
        rlBegin(RL_TRIANGLES);
            rlColor4ub(color.r, color.g, color.b, color.a);       
            
            // Front Face -----------------------------------------------------
            rlVertex3f(x-width/2, y-height/2, z+lenght/2);  // Bottom Left
            rlVertex3f(x+width/2, y-height/2, z+lenght/2);  // Bottom Right
            rlVertex3f(x-width/2, y+height/2, z+lenght/2);  // Top Left
            
            rlVertex3f(x+width/2, y+height/2, z+lenght/2);  // Top Right
            rlVertex3f(x-width/2, y+height/2, z+lenght/2);  // Top Left
            rlVertex3f(x+width/2, y-height/2, z+lenght/2);  // Bottom Right
            
            // Back Face ------------------------------------------------------
            rlVertex3f(x-width/2, y-height/2, z-lenght/2);  // Bottom Left
            rlVertex3f(x-width/2, y+height/2, z-lenght/2);  // Top Left
            rlVertex3f(x+width/2, y-height/2, z-lenght/2);  // Bottom Right
            
            rlVertex3f(x+width/2, y+height/2, z-lenght/2);  // Top Right
            rlVertex3f(x+width/2, y-height/2, z-lenght/2);  // Bottom Right
            rlVertex3f(x-width/2, y+height/2, z-lenght/2);  // Top Left
            
            // Top Face -------------------------------------------------------
            rlVertex3f(x-width/2, y+height/2, z-lenght/2);  // Top Left
            rlVertex3f(x-width/2, y+height/2, z+lenght/2);  // Bottom Left
            rlVertex3f(x+width/2, y+height/2, z+lenght/2);  // Bottom Right
            
            rlVertex3f(x+width/2, y+height/2, z-lenght/2);  // Top Right
            rlVertex3f(x-width/2, y+height/2, z-lenght/2);  // Top Left
            rlVertex3f(x+width/2, y+height/2, z+lenght/2);  // Bottom Right
            
            // Bottom Face ----------------------------------------------------
            rlVertex3f(x-width/2, y-height/2, z-lenght/2);  // Top Left
            rlVertex3f(x+width/2, y-height/2, z+lenght/2);  // Bottom Right
            rlVertex3f(x-width/2, y-height/2, z+lenght/2);  // Bottom Left
            
            rlVertex3f(x+width/2, y-height/2, z-lenght/2);  // Top Right
            rlVertex3f(x+width/2, y-height/2, z+lenght/2);  // Bottom Right
            rlVertex3f(x-width/2, y-height/2, z-lenght/2);  // Top Left
            
            // Right face -----------------------------------------------------
            rlVertex3f(x+width/2, y-height/2, z-lenght/2);  // Bottom Right
            rlVertex3f(x+width/2, y+height/2, z-lenght/2);  // Top Right
            rlVertex3f(x+width/2, y+height/2, z+lenght/2);  // Top Left
            
            rlVertex3f(x+width/2, y-height/2, z+lenght/2);  // Bottom Left
            rlVertex3f(x+width/2, y-height/2, z-lenght/2);  // Bottom Right
            rlVertex3f(x+width/2, y+height/2, z+lenght/2);  // Top Left
            
            // Left Face ------------------------------------------------------
            rlVertex3f(x-width/2, y-height/2, z-lenght/2);  // Bottom Right
            rlVertex3f(x-width/2, y+height/2, z+lenght/2);  // Top Left
            rlVertex3f(x-width/2, y+height/2, z-lenght/2);  // Top Right
            
            rlVertex3f(x-width/2, y-height/2, z+lenght/2);  // Bottom Left
            rlVertex3f(x-width/2, y+height/2, z+lenght/2);  // Top Left
            rlVertex3f(x-width/2, y-height/2, z-lenght/2);  // Bottom Right
        rlEnd();
    rlPopMatrix();
}

// Draw cube (Vector version)
void DrawCubeV(Vector3 position, Vector3 size, Color color)
{
    DrawCube(position, size.x, size.y, size.z, color);
}

// Draw cube wires
void DrawCubeWires(Vector3 position, float width, float height, float lenght, Color color)
{
    float x = position.x;
    float y = position.y;
    float z = position.z;
    
    rlPushMatrix();

        //rlRotatef(45, 0, 1, 0);
    
        rlBegin(RL_LINES);
            rlColor4ub(color.r, color.g, color.b, color.a);       
            
            // Front Face -----------------------------------------------------
            // Bottom Line
            rlVertex3f(x-width/2, y-height/2, z+lenght/2);  // Bottom Left
            rlVertex3f(x+width/2, y-height/2, z+lenght/2);  // Bottom Right
            
            // Left Line
            rlVertex3f(x+width/2, y-height/2, z+lenght/2);  // Bottom Right
            rlVertex3f(x+width/2, y+height/2, z+lenght/2);  // Top Right
            
            // Top Line
            rlVertex3f(x+width/2, y+height/2, z+lenght/2);  // Top Right
            rlVertex3f(x-width/2, y+height/2, z+lenght/2);  // Top Left
            
            // Right Line
            rlVertex3f(x-width/2, y+height/2, z+lenght/2);  // Top Left
            rlVertex3f(x-width/2, y-height/2, z+lenght/2);  // Bottom Left
                
            // Back Face ------------------------------------------------------
            // Bottom Line
            rlVertex3f(x-width/2, y-height/2, z-lenght/2);  // Bottom Left
            rlVertex3f(x+width/2, y-height/2, z-lenght/2);  // Bottom Right
            
            // Left Line
            rlVertex3f(x+width/2, y-height/2, z-lenght/2);  // Bottom Right
            rlVertex3f(x+width/2, y+height/2, z-lenght/2);  // Top Right
            
            // Top Line
            rlVertex3f(x+width/2, y+height/2, z-lenght/2);  // Top Right
            rlVertex3f(x-width/2, y+height/2, z-lenght/2);  // Top Left
            
            // Right Line
            rlVertex3f(x-width/2, y+height/2, z-lenght/2);  // Top Left
            rlVertex3f(x-width/2, y-height/2, z-lenght/2);  // Bottom Left
            
            // Top Face -------------------------------------------------------
            // Left Line
            rlVertex3f(x-width/2, y+height/2, z+lenght/2);  // Top Left Front
            rlVertex3f(x-width/2, y+height/2, z-lenght/2);  // Top Left Back
            
            // Right Line
            rlVertex3f(x+width/2, y+height/2, z+lenght/2);  // Top Right Front
            rlVertex3f(x+width/2, y+height/2, z-lenght/2);  // Top Right Back

            // Bottom Face  ---------------------------------------------------
            // Left Line
            rlVertex3f(x-width/2, y-height/2, z+lenght/2);  // Top Left Front
            rlVertex3f(x-width/2, y-height/2, z-lenght/2);  // Top Left Back
            
            // Right Line
            rlVertex3f(x+width/2, y-height/2, z+lenght/2);  // Top Right Front
            rlVertex3f(x+width/2, y-height/2, z-lenght/2);  // Top Right Back
        rlEnd();
    rlPopMatrix();
}

// Draw cube
// NOTE: Cube position is the center position
void DrawCubeTexture(Texture2D texture, Vector3 position, float width, float height, float lenght, Color color)
{
    float x = position.x;
    float y = position.y;
    float z = position.z;

    rlEnableTexture(texture.glId);
    
    rlPushMatrix();      
        // NOTE: Be careful! Function order matters (scale, translate, rotate)
        //rlScalef(2.0f, 2.0f, 2.0f);
        //rlTranslatef(2.0f, 0.0f, 0.0f);
        //rlRotatef(45, 0, 1, 0);
    
        rlBegin(RL_QUADS);
            rlColor4ub(color.r, color.g, color.b, color.a);           
            // Front Face
            rlNormal3f(0.0f, 0.0f, 1.0f);                  // Normal Pointing Towards Viewer
            rlTexCoord2f(0.0f, 0.0f); rlVertex3f(x-width/2, y-height/2, z+lenght/2);  // Bottom Left Of The Texture and Quad
            rlTexCoord2f(1.0f, 0.0f); rlVertex3f(x+width/2, y-height/2, z+lenght/2);  // Bottom Right Of The Texture and Quad
            rlTexCoord2f(1.0f, 1.0f); rlVertex3f(x+width/2, y+height/2, z+lenght/2);  // Top Right Of The Texture and Quad
            rlTexCoord2f(0.0f, 1.0f); rlVertex3f(x-width/2, y+height/2, z+lenght/2);  // Top Left Of The Texture and Quad
            // Back Face
            rlNormal3f( 0.0f, 0.0f,-1.0f);                  // Normal Pointing Away From Viewer
            rlTexCoord2f(1.0f, 0.0f); rlVertex3f(x-width/2, y-height/2, z-lenght/2);  // Bottom Right Of The Texture and Quad
            rlTexCoord2f(1.0f, 1.0f); rlVertex3f(x-width/2, y+height/2, z-lenght/2);  // Top Right Of The Texture and Quad
            rlTexCoord2f(0.0f, 1.0f); rlVertex3f(x+width/2, y+height/2, z-lenght/2);  // Top Left Of The Texture and Quad
            rlTexCoord2f(0.0f, 0.0f); rlVertex3f(x+width/2, y-height/2, z-lenght/2);  // Bottom Left Of The Texture and Quad
            // Top Face
            rlNormal3f( 0.0f, 1.0f, 0.0f);                  // Normal Pointing Up
            rlTexCoord2f(0.0f, 1.0f); rlVertex3f(x-width/2, y+height/2, z-lenght/2);  // Top Left Of The Texture and Quad
            rlTexCoord2f(0.0f, 0.0f); rlVertex3f(x-width/2, y+height/2, z+lenght/2);  // Bottom Left Of The Texture and Quad
            rlTexCoord2f(1.0f, 0.0f); rlVertex3f(x+width/2, y+height/2, z+lenght/2);  // Bottom Right Of The Texture and Quad
            rlTexCoord2f(1.0f, 1.0f); rlVertex3f(x+width/2, y+height/2, z-lenght/2);  // Top Right Of The Texture and Quad
            // Bottom Face
            rlNormal3f( 0.0f,-1.0f, 0.0f);                  // Normal Pointing Down
            rlTexCoord2f(1.0f, 1.0f); rlVertex3f(x-width/2, y-height/2, z-lenght/2);  // Top Right Of The Texture and Quad
            rlTexCoord2f(0.0f, 1.0f); rlVertex3f(x+width/2, y-height/2, z-lenght/2);  // Top Left Of The Texture and Quad
            rlTexCoord2f(0.0f, 0.0f); rlVertex3f(x+width/2, y-height/2, z+lenght/2);  // Bottom Left Of The Texture and Quad
            rlTexCoord2f(1.0f, 0.0f); rlVertex3f(x-width/2, y-height/2, z+lenght/2);  // Bottom Right Of The Texture and Quad
            // Right face
            rlNormal3f( 1.0f, 0.0f, 0.0f);                  // Normal Pointing Right
            rlTexCoord2f(1.0f, 0.0f); rlVertex3f(x+width/2, y-height/2, z-lenght/2);  // Bottom Right Of The Texture and Quad
            rlTexCoord2f(1.0f, 1.0f); rlVertex3f(x+width/2, y+height/2, z-lenght/2);  // Top Right Of The Texture and Quad
            rlTexCoord2f(0.0f, 1.0f); rlVertex3f(x+width/2, y+height/2, z+lenght/2);  // Top Left Of The Texture and Quad
            rlTexCoord2f(0.0f, 0.0f); rlVertex3f(x+width/2, y-height/2, z+lenght/2);  // Bottom Left Of The Texture and Quad
            // Left Face
            rlNormal3f(-1.0f, 0.0f, 0.0f);                  // Normal Pointing Left
            rlTexCoord2f(0.0f, 0.0f); rlVertex3f(x-width/2, y-height/2, z-lenght/2);  // Bottom Left Of The Texture and Quad
            rlTexCoord2f(1.0f, 0.0f); rlVertex3f(x-width/2, y-height/2, z+lenght/2);  // Bottom Right Of The Texture and Quad
            rlTexCoord2f(1.0f, 1.0f); rlVertex3f(x-width/2, y+height/2, z+lenght/2);  // Top Right Of The Texture and Quad
            rlTexCoord2f(0.0f, 1.0f); rlVertex3f(x-width/2, y+height/2, z-lenght/2);  // Top Left Of The Texture and Quad
        rlEnd();
    rlPopMatrix();
    
    rlDisableTexture();
}

// Draw sphere
void DrawSphere(Vector3 centerPos, float radius, Color color)
{
    DrawSphereEx(centerPos, radius, 16, 16, color);
}

// Draw sphere with extended parameters
void DrawSphereEx(Vector3 centerPos, float radius, int rings, int slices, Color color)
{
    rlPushMatrix();
        rlTranslatef(centerPos.x, centerPos.y, centerPos.z);
        //rlRotatef(rotation, 0, 1, 0);
        rlScalef(radius, radius, radius);
        
        rlBegin(RL_TRIANGLES);
            rlColor4ub(color.r, color.g, color.b, color.a);
            
            for(int i = 0; i < 2 * rings + 1; i ++)
            {
                for(int j = 0; j < slices; j++)
                {
                    rlVertex3f(cos(DEG2RAD*(270+(90/rings)*i)) * sin(DEG2RAD*(j*360/slices)) * radius, 
                               sin(DEG2RAD*(270+(90/rings)*i)) * radius, 
                               cos(DEG2RAD*(270+(90/rings)*i)) * cos(DEG2RAD*(j*360/slices)) * radius);
                    rlVertex3f(cos(DEG2RAD*(270+(90/rings)*(i+1))) * sin(DEG2RAD*((j+1)*360/slices)) * radius, 
                               sin(DEG2RAD*(270+(90/rings)*(i+1))) * radius, 
                               cos(DEG2RAD*(270+(90/rings)*(i+1))) * cos(DEG2RAD*((j+1)*360/slices)) * radius);
                    rlVertex3f(cos(DEG2RAD*(270+(90/rings)*(i+1))) * sin(DEG2RAD*(j*360/slices)) * radius, 
                               sin(DEG2RAD*(270+(90/rings)*(i+1))) * radius, 
                               cos(DEG2RAD*(270+(90/rings)*(i+1))) * cos(DEG2RAD*(j*360/slices)) * radius);

                    rlVertex3f(cos(DEG2RAD*(270+(90/rings)*i)) * sin(DEG2RAD*(j*360/slices)) * radius, 
                               sin(DEG2RAD*(270+(90/rings)*i)) * radius, 
                               cos(DEG2RAD*(270+(90/rings)*i)) * cos(DEG2RAD*(j*360/slices)) * radius);
                    rlVertex3f(cos(DEG2RAD*(270+(90/rings)*(i))) * sin(DEG2RAD*((j+1)*360/slices)) * radius, 
                               sin(DEG2RAD*(270+(90/rings)*(i))) * radius, 
                               cos(DEG2RAD*(270+(90/rings)*(i))) * cos(DEG2RAD*((j+1)*360/slices)) * radius);
                    rlVertex3f(cos(DEG2RAD*(270+(90/rings)*(i+1))) * sin(DEG2RAD*((j+1)*360/slices)) * radius, 
                               sin(DEG2RAD*(270+(90/rings)*(i+1))) * radius, 
                               cos(DEG2RAD*(270+(90/rings)*(i+1))) * cos(DEG2RAD*((j+1)*360/slices)) * radius);
                }
            }
        rlEnd();
    rlPopMatrix();
}

// Draw sphere wires
void DrawSphereWires(Vector3 centerPos, float radius, int rings, int slices, Color color)
{
    rlPushMatrix();
        rlTranslatef(centerPos.x, centerPos.y, centerPos.z);
        //rlRotatef(rotation, 0, 1, 0);
        rlScalef(radius, radius, radius);
        
        rlBegin(RL_LINES);
            rlColor4ub(color.r, color.g, color.b, color.a);
            
            for(int i = 0; i < 2 * rings + 1; i ++)
            {
                for(int j = 0; j < slices; j++)
                {
                    rlVertex3f(cos(DEG2RAD*(270+(90/rings)*i)) * sin(DEG2RAD*(j*360/slices)) * radius, 
                               sin(DEG2RAD*(270+(90/rings)*i)) * radius, 
                               cos(DEG2RAD*(270+(90/rings)*i)) * cos(DEG2RAD*(j*360/slices)) * radius);
                    rlVertex3f(cos(DEG2RAD*(270+(90/rings)*(i+1))) * sin(DEG2RAD*((j+1)*360/slices)) * radius, 
                               sin(DEG2RAD*(270+(90/rings)*(i+1))) * radius, 
                               cos(DEG2RAD*(270+(90/rings)*(i+1))) * cos(DEG2RAD*((j+1)*360/slices)) * radius);
                    
                    rlVertex3f(cos(DEG2RAD*(270+(90/rings)*(i+1))) * sin(DEG2RAD*((j+1)*360/slices)) * radius, 
                               sin(DEG2RAD*(270+(90/rings)*(i+1))) * radius, 
                               cos(DEG2RAD*(270+(90/rings)*(i+1))) * cos(DEG2RAD*((j+1)*360/slices)) * radius);
                    rlVertex3f(cos(DEG2RAD*(270+(90/rings)*(i+1))) * sin(DEG2RAD*(j*360/slices)) * radius, 
                               sin(DEG2RAD*(270+(90/rings)*(i+1))) * radius, 
                               cos(DEG2RAD*(270+(90/rings)*(i+1))) * cos(DEG2RAD*(j*360/slices)) * radius);
                    
                    rlVertex3f(cos(DEG2RAD*(270+(90/rings)*(i+1))) * sin(DEG2RAD*(j*360/slices)) * radius, 
                               sin(DEG2RAD*(270+(90/rings)*(i+1))) * radius, 
                               cos(DEG2RAD*(270+(90/rings)*(i+1))) * cos(DEG2RAD*(j*360/slices)) * radius);
                    rlVertex3f(cos(DEG2RAD*(270+(90/rings)*i)) * sin(DEG2RAD*(j*360/slices)) * radius, 
                               sin(DEG2RAD*(270+(90/rings)*i)) * radius, 
                               cos(DEG2RAD*(270+(90/rings)*i)) * cos(DEG2RAD*(j*360/slices)) * radius);
                }
            }
        rlEnd();
    rlPopMatrix();
}

// Draw a cylinder
// NOTE: It could be also used for pyramid and cone
void DrawCylinder(Vector3 position, float radiusTop, float radiusBottom, float height, int sides, Color color)
{
    if (sides < 3) sides = 3;
    
    rlPushMatrix();
        rlTranslatef(position.x, position.y, position.z);

        rlBegin(RL_TRIANGLES);
            rlColor4ub(color.r, color.g, color.b, color.a);

            if (radiusTop > 0)
            {
                // Draw Body -------------------------------------------------------------------------------------
                for(int i = 0; i < 360; i += 360/sides)
                {
                    rlVertex3f(sin(DEG2RAD*i) * radiusBottom, 0, cos(DEG2RAD*i) * radiusBottom); //Bottom Left
                    rlVertex3f(sin(DEG2RAD*(i+360/sides)) * radiusBottom, 0, cos(DEG2RAD*(i+360/sides)) * radiusBottom); //Bottom Right
                    rlVertex3f(sin(DEG2RAD*(i+360/sides)) * radiusTop, height, cos(DEG2RAD*(i+360/sides)) * radiusTop); //Top Right
                    
                    rlVertex3f(sin(DEG2RAD*i) * radiusTop, height, cos(DEG2RAD*i) * radiusTop); //Top Left
                    rlVertex3f(sin(DEG2RAD*i) * radiusBottom, 0, cos(DEG2RAD*i) * radiusBottom); //Bottom Left
                    rlVertex3f(sin(DEG2RAD*(i+360/sides)) * radiusTop, height, cos(DEG2RAD*(i+360/sides)) * radiusTop); //Top Right
                }
                
                // Draw Cap --------------------------------------------------------------------------------------
                for(int i = 0; i < 360; i += 360/sides)
                {
                    rlVertex3f(0, height, 0);
                    rlVertex3f(sin(DEG2RAD*i) * radiusTop, height, cos(DEG2RAD*i) * radiusTop);
                    rlVertex3f(sin(DEG2RAD*(i+360/sides)) * radiusTop, height, cos(DEG2RAD*(i+360/sides)) * radiusTop);
                }
            }
            else
            {
                // Draw Cone -------------------------------------------------------------------------------------
                for(int i = 0; i < 360; i += 360/sides)
                {
                    rlVertex3f(0, height, 0);
                    rlVertex3f(sin(DEG2RAD*i) * radiusBottom, 0, cos(DEG2RAD*i) * radiusBottom);
                    rlVertex3f(sin(DEG2RAD*(i+360/sides)) * radiusBottom, 0, cos(DEG2RAD*(i+360/sides)) * radiusBottom);
                }
            }
            
            // Draw Base -----------------------------------------------------------------------------------------
            for(int i = 0; i < 360; i += 360/sides)
            {
                rlVertex3f(0, 0, 0);
                rlVertex3f(sin(DEG2RAD*(i+360/sides)) * radiusBottom, 0, cos(DEG2RAD*(i+360/sides)) * radiusBottom);
                rlVertex3f(sin(DEG2RAD*i) * radiusBottom, 0, cos(DEG2RAD*i) * radiusBottom);
            }
        rlEnd();    
    rlPopMatrix();
}

// Draw a wired cylinder
// NOTE: It could be also used for pyramid and cone
void DrawCylinderWires(Vector3 position, float radiusTop, float radiusBottom, float height, int sides, Color color)
{
    if(sides < 3) sides = 3;
    
    rlPushMatrix();
        rlTranslatef(position.x, position.y, position.z);
        
        rlBegin(RL_LINES);
            rlColor4ub(color.r, color.g, color.b, color.a);
          
            for(int i = 0; i < 360; i += 360/sides)
            {
                rlVertex3f(sin(DEG2RAD*i) * radiusBottom, 0, cos(DEG2RAD*i) * radiusBottom);
                rlVertex3f(sin(DEG2RAD*(i+360/sides)) * radiusBottom, 0, cos(DEG2RAD*(i+360/sides)) * radiusBottom);
                
                rlVertex3f(sin(DEG2RAD*(i+360/sides)) * radiusBottom, 0, cos(DEG2RAD*(i+360/sides)) * radiusBottom);
                rlVertex3f(sin(DEG2RAD*(i+360/sides)) * radiusTop, height, cos(DEG2RAD*(i+360/sides)) * radiusTop);
                
                rlVertex3f(sin(DEG2RAD*(i+360/sides)) * radiusTop, height, cos(DEG2RAD*(i+360/sides)) * radiusTop);
                rlVertex3f(sin(DEG2RAD*i) * radiusTop, height, cos(DEG2RAD*i) * radiusTop);
                
                rlVertex3f(sin(DEG2RAD*i) * radiusTop, height, cos(DEG2RAD*i) * radiusTop);
                rlVertex3f(sin(DEG2RAD*i) * radiusBottom, 0, cos(DEG2RAD*i) * radiusBottom);
            }
        rlEnd();
    rlPopMatrix();
}

// Draw a plane
// TODO: Test this function
void DrawPlane(Vector3 centerPos, Vector2 size, Vector3 rotation, Color color)
{
    // NOTE: Plane is always created on XZ ground and then rotated
    rlPushMatrix();
        rlTranslatef(centerPos.x, centerPos.y, centerPos.z);
        
        // TODO: Review multiples rotations Gimbal-Lock... use matrix or quaternions...
        rlRotatef(rotation.x, 1, 0, 0);
        rlRotatef(rotation.y, 0, 1, 0);
        rlRotatef(rotation.z, 0, 0, 1);
        rlScalef(size.x, 1.0f, size.y);
    
        rlBegin(RL_QUADS);
            rlColor4ub(color.r, color.g, color.b, color.a);
            rlNormal3f(0.0f, 1.0f, 0.0f); 
            rlTexCoord2f(0.0f, 0.0f); rlVertex3f(-0.5f, 0.0f, -0.5f);
            rlTexCoord2f(1.0f, 0.0f); rlVertex3f(0.5f, 0.0f, -0.5f);
            rlTexCoord2f(1.0f, 1.0f); rlVertex3f(0.5f, 0.0f, 0.5f);
            rlTexCoord2f(0.0f, 1.0f); rlVertex3f(-0.5f, 0.0f, 0.5f);
        rlEnd();
    rlPopMatrix();
}

// Draw a plane with divisions
// TODO: Test this function
void DrawPlaneEx(Vector3 centerPos, Vector2 size, Vector3 rotation, int slicesX, int slicesZ, Color color)
{
    float quadWidth = size.x / slicesX;
    float quadLenght = size.y / slicesZ;
    
    float texPieceW = 1 / size.x;
    float texPieceH = 1 / size.y;

    // NOTE: Plane is always created on XZ ground and then rotated
    rlPushMatrix();
        rlTranslatef(-size.x / 2, 0.0f, -size.y / 2);
        rlTranslatef(centerPos.x, centerPos.y, centerPos.z);
        
        // TODO: Review multiples rotations Gimbal-Lock... use matrix or quaternions...
        rlRotatef(rotation.x, 1, 0, 0);
        rlRotatef(rotation.y, 0, 1, 0);
        rlRotatef(rotation.z, 0, 0, 1);
    
        rlBegin(RL_QUADS);
            rlColor4ub(color.r, color.g, color.b, color.a);
            rlNormal3f(0.0f, 1.0f, 0.0f);
            
            for (int z = 0; z < slicesZ; z++)
            {
                for (int x = 0; x < slicesX; x++)
                {
                    // Draw the plane quad by quad (with textcoords)
                    rlTexCoord2f((float)x * texPieceW, (float)z * texPieceH);
                    rlVertex3f((float)x * quadWidth, 0.0f, (float)z * quadLenght);
                    
                    rlTexCoord2f((float)x * texPieceW + texPieceW, (float)z * texPieceH);
                    rlVertex3f((float)x * quadWidth  + quadWidth, 0.0f, (float)z * quadLenght);
                    
                    rlTexCoord2f((float)x * texPieceW + texPieceW, (float)z * texPieceH + texPieceH);
                    rlVertex3f((float)x * quadWidth + quadWidth, 0.0f, (float)z * quadLenght + quadLenght);
                    
                    rlTexCoord2f((float)x * texPieceW, (float)z * texPieceH + texPieceH);
                    rlVertex3f((float)x * quadWidth, 0.0f, (float)z * quadLenght + quadLenght);
                }
            }
        rlEnd();

    rlPopMatrix();
}

// Draw a grid centered at (0, 0, 0)
void DrawGrid(int slices, float spacing)
{
    int halfSlices = slices / 2;

    rlBegin(RL_LINES);
        for(int i = -halfSlices; i <= halfSlices; i++)
        {
            if (i == 0)
            {
                rlColor3f(0.5f, 0.5f, 0.5f);
                rlColor3f(0.5f, 0.5f, 0.5f);
                rlColor3f(0.5f, 0.5f, 0.5f);
                rlColor3f(0.5f, 0.5f, 0.5f);
            }
            else
            {
                rlColor3f(0.75f, 0.75f, 0.75f);
                rlColor3f(0.75f, 0.75f, 0.75f);
                rlColor3f(0.75f, 0.75f, 0.75f);
                rlColor3f(0.75f, 0.75f, 0.75f);
            }
            
            rlVertex3f((float)i*spacing, 0.0f, (float)-halfSlices*spacing);
            rlVertex3f((float)i*spacing, 0.0f, (float)halfSlices*spacing);

            rlVertex3f((float)-halfSlices*spacing, 0.0f, (float)i*spacing);
            rlVertex3f((float)halfSlices*spacing, 0.0f, (float)i*spacing);
        }
    rlEnd();
}

// Draw gizmo
void DrawGizmo(Vector3 position)
{
    // NOTE: RGB = XYZ
    float lenght = 1.0f;

    rlPushMatrix();
        rlTranslatef(position.x, position.y, position.z);
        //rlRotatef(rotation, 0, 1, 0);
        rlScalef(lenght, lenght, lenght);
    
        rlBegin(RL_LINES);
            rlColor3f(1.0f, 0.0f, 0.0f); rlVertex3f(0.0f, 0.0f, 0.0f);
            rlColor3f(1.0f, 0.0f, 0.0f); rlVertex3f(1.0f, 0.0f, 0.0f);
            
            rlColor3f(0.0f, 1.0f, 0.0f); rlVertex3f(0.0f, 0.0f, 0.0f);
            rlColor3f(0.0f, 1.0f, 0.0f); rlVertex3f(0.0f, 1.0f, 0.0f);
            
            rlColor3f(0.0f, 0.0f, 1.0f); rlVertex3f(0.0f, 0.0f, 0.0f);
            rlColor3f(0.0f, 0.0f, 1.0f); rlVertex3f(0.0f, 0.0f, 1.0f);
        rlEnd();    
    rlPopMatrix();
}

void DrawGizmoEx(Vector3 position, Vector3 rotation, float scale, bool orbits)
{
    // NOTE: RGB = XYZ
    rlPushMatrix();
        rlTranslatef(position.x, position.y, position.z);
        rlScalef(scale, scale, scale);
        
        if(rotation.x) rlRotatef(rotation.x, 1, 0, 0);
        if(rotation.y) rlRotatef(rotation.y, 0, 1, 0);
        if(rotation.z) rlRotatef(rotation.z, 0, 0, 1);
    
        rlBegin(RL_LINES);
            // X Axis
            rlColor4ub(200, 0, 0, 255); // RED
            rlVertex3f(position.x, position.y, position.z);
            rlVertex3f(position.x + 1, position.y, position.z);
            
            // ArrowX
            rlVertex3f(position.x + 1.1, position.y, position.z);
            rlVertex3f(position.x + .9, position.y, position.z + .1);
            
            rlVertex3f(position.x + 1.1, position.y, position.z);
            rlVertex3f(position.x + .9, position.y, position.z - .1);
            
            // Y Axis
            rlColor4ub(0, 200, 0, 255); // GREEN
            rlVertex3f(position.x, position.y, position.z);
            rlVertex3f(position.x, position.y + 1, position.z);
            
            // ArrowY
            rlVertex3f(position.x, position.y + 1.1, position.z);
            rlVertex3f(position.x + .1, position.y + .9, position.z);
            
            rlVertex3f(position.x, position.y + 1.1, position.z);
            rlVertex3f(position.x - .1, position.y + .9, position.z);
            
            // Z Axis
            rlColor4ub(0, 0, 200, 255); // BLUE
            rlVertex3f(position.x, position.y, position.z);
            rlVertex3f(position.x, position.y, position.z - 1);
            
            // ArrowZ
            rlVertex3f(position.x, position.y, position.z - 1.1);
            rlVertex3f(position.x + .1, position.y, position.z - .9);
            
            rlVertex3f(position.x, position.y, position.z - 1.1);
            rlVertex3f(position.x - .1, position.y, position.z - .9);
            
            // Extra
            if(orbits)
            {
                int n = 3;
                
                // X Axis
                rlColor4ub(200, 0, 0, 255); // RED
                for (int i=0; i < 360; i++)
                {
                    rlVertex3f(0, position.x + sin(DEG2RAD*i) * scale/n, position.y + cos(DEG2RAD*i) * scale/n);
                    rlVertex3f(0,position.x + sin(DEG2RAD*(i+1)) * scale/n, position.y + cos(DEG2RAD*(i+1)) * scale/n);
                }
                
                // Y Axis
                rlColor4ub(0, 200, 0, 255); // GREEN
                for (int i=0; i < 360; i++)
                {
                    rlVertex3f(position.x + sin(DEG2RAD*i) * scale/n, 0, position.y + cos(DEG2RAD*i) * scale/n);
                    rlVertex3f(position.x + sin(DEG2RAD*(i+1)) * scale/n, 0, position.y + cos(DEG2RAD*(i+1)) * scale/n);
                }
                
                // Z Axis
                rlColor4ub(0, 0, 200, 255); // BLUE
                for (int i=0; i < 360; i++)
                {
                    rlVertex3f(position.x + sin(DEG2RAD*i) * scale/n, position.y + cos(DEG2RAD*i) * scale/n, 0);
                    rlVertex3f(position.x + sin(DEG2RAD*(i+1)) * scale/n, position.y + cos(DEG2RAD*(i+1)) * scale/n, 0);
                }
            }
        rlEnd();
    rlPopMatrix();
}

// Load a 3d model (.OBJ)
// TODO: Add comments explaining this function process
Model LoadModel(const char *fileName)                                    
{
    VertexData vData;
    
    char dataType;
    char comments[200];
    
    int numVertex = 0;
    int numNormals = 0;
    int numTexCoords = 0;
    int numTriangles = 0;

    FILE* objFile;

    objFile = fopen(fileName, "rt");
    
    while(!feof(objFile))
    {
        fscanf(objFile, "%c", &dataType);
        
        switch(dataType)
        {
            case '#':         // It's a comment
            {
                fgets(comments, 200, objFile);                
            } break;
            case 'v': 
            {
                fscanf(objFile, "%c", &dataType);
                
                if (dataType == 't')    // Read texCoord
                {
                    fgets(comments, 200, objFile);
                    fscanf(objFile, "%c", &dataType);
                
                    while (dataType == 'v')
                    {
                        fgets(comments, 200, objFile);
                        fscanf(objFile, "%c", &dataType);
                    }
                    
                    if (dataType == '#')
                    {
                        fscanf(objFile, "%i", &numTexCoords);
                    }
                    else printf("Ouch! Something was wrong...");
                    
                    fgets(comments, 200, objFile);
                }
                else if (dataType == 'n')    // Read normals
                {
                    fgets(comments, 200, objFile);
                    fscanf(objFile, "%c", &dataType);
                
                    while (dataType == 'v')
                    {
                        fgets(comments, 200, objFile);
                        fscanf(objFile, "%c", &dataType);
                    }
                    
                    if (dataType == '#')
                    {
                        fscanf(objFile, "%i", &numNormals);
                    }
                    else printf("Ouch! Something was wrong...");
                
                    fgets(comments, 200, objFile);
                }
                else    // Read vertex
                {
                    fgets(comments, 200, objFile);
                    fscanf(objFile, "%c", &dataType);
                
                    while (dataType == 'v')
                    {
                        fgets(comments, 200, objFile);
                        fscanf(objFile, "%c", &dataType);
                    }
                    
                    if (dataType == '#')
                    {
                        fscanf(objFile, "%i", &numVertex);
                    }
                    else printf("Ouch! Something was wrong...");
                    
                    fgets(comments, 200, objFile);
                }
            } break;
            case 'f':
            {
                fgets(comments, 200, objFile);
                fscanf(objFile, "%c", &dataType);
            
                while (dataType == 'f')
                {
                    fgets(comments, 200, objFile);
                    fscanf(objFile, "%c", &dataType);
                }
                
                if (dataType == '#')
                {
                    fscanf(objFile, "%i", &numTriangles);
                }
                else printf("Ouch! Something was wrong...");
                
                fgets(comments, 200, objFile);
            
            } break;
            default: break;
        }
    }
    
    Vector3 midVertices[numVertex];
    Vector3 midNormals[numNormals];
    Vector2 midTexCoords[numTexCoords];
    
    vData.numVertices = numTriangles*3;
    
    vData.vertices = (float *)malloc(vData.numVertices * 3 * sizeof(float));
    vData.texcoords = (float *)malloc(vData.numVertices * 2 * sizeof(float));
    vData.normals = (float *)malloc(vData.numVertices * 3 * sizeof(float));
    
    int countVertex = 0;
    int countNormals = 0;
    int countTexCoords = 0;
    
    int vCounter = 0;       // Used to count vertices float by float
    int tcCounter = 0;      // Used to count texcoords float by float
    int nCounter = 0;       // Used to count normals float by float
    
    rewind(objFile);
    
    while(!feof(objFile))
    {
        fscanf(objFile, "%c", &dataType);
        
        switch(dataType)
        {
            case '#': 
            {
                fgets(comments, 200, objFile);                
            } break;
            case 'v': 
            {
                fscanf(objFile, "%c", &dataType);
                
                if (dataType == 't')    // Read texCoord
                {
                    float useless = 0;
                
                    fscanf(objFile, "%f %f %f", &midTexCoords[countTexCoords].x, &midTexCoords[countTexCoords].y, &useless);
                    countTexCoords++;
                    
                    fscanf(objFile, "%c", &dataType);
                }
                else if (dataType == 'n')    // Read normals
                {
                    fscanf(objFile, "%f %f %f", &midNormals[countNormals].x, &midNormals[countNormals].y, &midNormals[countNormals].z );
                    countNormals++;
                    
                    fscanf(objFile, "%c", &dataType);
                }
                else    // Read vertex
                {
                    fscanf(objFile, "%f %f %f", &midVertices[countVertex].x, &midVertices[countVertex].y, &midVertices[countVertex].z );
                    countVertex++;
                    
                    fscanf(objFile, "%c", &dataType);
                }
            } break;
            case 'f':
            {
                // At this point all vertex data (v, vt, vn) have been gathered on midVertices, midTexCoords, midNormals
                // Now we can organize that data into our VertexData struct
            
                int vNum, vtNum, vnNum;
                fscanf(objFile, "%c", &dataType);
                fscanf(objFile, "%i/%i/%i", &vNum, &vtNum, &vnNum);
                
                vData.vertices[vCounter] = midVertices[vNum-1].x;
                vData.vertices[vCounter + 1] = midVertices[vNum-1].y;
                vData.vertices[vCounter + 2] = midVertices[vNum-1].z;
                vCounter += 3;
                
                vData.normals[nCounter] = midNormals[vnNum-1].x;
                vData.normals[nCounter + 1] = midNormals[vnNum-1].y;
                vData.normals[nCounter + 2] = midNormals[vnNum-1].z;
                nCounter += 3;
                
                vData.texcoords[tcCounter] = midTexCoords[vtNum-1].x;
                vData.texcoords[tcCounter + 1] = -midTexCoords[vtNum-1].y;
                tcCounter += 2;

                fscanf(objFile, "%i/%i/%i", &vNum, &vtNum, &vnNum);
                
                vData.vertices[vCounter] = midVertices[vNum-1].x;
                vData.vertices[vCounter + 1] = midVertices[vNum-1].y;
                vData.vertices[vCounter + 2] = midVertices[vNum-1].z;
                vCounter += 3;
                
                vData.normals[nCounter] = midNormals[vnNum-1].x;
                vData.normals[nCounter + 1] = midNormals[vnNum-1].y;
                vData.normals[nCounter + 2] = midNormals[vnNum-1].z;
                nCounter += 3;
                
                vData.texcoords[tcCounter] = midTexCoords[vtNum-1].x;
                vData.texcoords[tcCounter + 1] = -midTexCoords[vtNum-1].y;
                tcCounter += 2;
                
                fscanf(objFile, "%i/%i/%i", &vNum, &vtNum, &vnNum);
                
                vData.vertices[vCounter] = midVertices[vNum-1].x;
                vData.vertices[vCounter + 1] = midVertices[vNum-1].y;
                vData.vertices[vCounter + 2] = midVertices[vNum-1].z;
                vCounter += 3;
                
                vData.normals[nCounter] = midNormals[vnNum-1].x;
                vData.normals[nCounter + 1] = midNormals[vnNum-1].y;
                vData.normals[nCounter + 2] = midNormals[vnNum-1].z;
                nCounter += 3;
                
                vData.texcoords[tcCounter] = midTexCoords[vtNum-1].x;
                vData.texcoords[tcCounter + 1] = -midTexCoords[vtNum-1].y;
                tcCounter += 2;
            } break;
            default: break;
        }
    }
    
    fclose(objFile);
    
    // NOTE: At this point we have all vertex, texcoord, normal data for the model in vData struct

    Model model;

#ifdef USE_OPENGL_11
    model.data = vData;      // model data is vertex data  
#else   
    model.vaoId = rlglLoadModel(vData);     // Use loaded data to generate VAO
    
    // Now that vertex data is uploaded to GPU, we can free arrays
    free(vData.vertices);
    free(vData.texcoords);
    free(vData.normals);
#endif

    return model;
}

// Load a heightmap image as a 3d model
Model LoadHeightmap(Image heightmap, float maxHeight)
{
    VertexData vData;

    int mapX = heightmap.width;
    int mapZ = heightmap.height;
    
    // NOTE: One vertex per pixel
    // TODO: Consider resolution when generating model data?
    int numTriangles = (mapX-1)*(mapZ-1)*2;    // One quad every four pixels
  
    vData.numVertices = numTriangles*3;

    vData.vertices = (float *)malloc(vData.numVertices * 3 * sizeof(float));
    vData.normals = (float *)malloc(vData.numVertices * 3 * sizeof(float));
    vData.texcoords = (float *)malloc(vData.numVertices * 2 * sizeof(float));
    
    int vCounter = 0;       // Used to count vertices float by float
    int tcCounter = 0;      // Used to count texcoords float by float
    int nCounter = 0;       // Used to count normals float by float
    
    int trisCounter = 0;
    
    float scaleFactor = maxHeight/255;    // TODO: Review scaleFactor calculation

    for(int z = 0; z < mapZ-1; z++)
    {
        for(int x = 0; x < mapX-1; x++)
        {
            // Fill vertices array with data
            //----------------------------------------------------------
            
            // one triangle - 3 vertex
            vData.vertices[vCounter] = x;
            vData.vertices[vCounter + 1] = GetHeightValue(heightmap.pixels[x + z*mapX])*scaleFactor;
            vData.vertices[vCounter + 2] = z;
            
            vData.vertices[vCounter + 3] = x;
            vData.vertices[vCounter + 4] = GetHeightValue(heightmap.pixels[x + (z+1)*mapX])*scaleFactor;
            vData.vertices[vCounter + 5] = z+1;
            
            vData.vertices[vCounter + 6] = x+1;
            vData.vertices[vCounter + 7] = GetHeightValue(heightmap.pixels[(x+1) + z*mapX])*scaleFactor;
            vData.vertices[vCounter + 8] = z;
            
            // another triangle - 3 vertex
            vData.vertices[vCounter + 9] = vData.vertices[vCounter + 6];
            vData.vertices[vCounter + 10] = vData.vertices[vCounter + 7];
            vData.vertices[vCounter + 11] = vData.vertices[vCounter + 8];
            
            vData.vertices[vCounter + 12] = vData.vertices[vCounter + 3];
            vData.vertices[vCounter + 13] = vData.vertices[vCounter + 4];
            vData.vertices[vCounter + 14] = vData.vertices[vCounter + 5];
            
            vData.vertices[vCounter + 15] = x+1;
            vData.vertices[vCounter + 16] = GetHeightValue(heightmap.pixels[(x+1) + (z+1)*mapX])*scaleFactor;
            vData.vertices[vCounter + 17] = z+1;
            vCounter += 18;     // 6 vertex, 18 floats
            
            // Fill texcoords array with data
            //--------------------------------------------------------------
            vData.texcoords[tcCounter] = (float)x / (mapX-1);
            vData.texcoords[tcCounter + 1] = (float)z / (mapZ-1);
            
            vData.texcoords[tcCounter + 2] = (float)x / (mapX-1);
            vData.texcoords[tcCounter + 3] = (float)(z+1) / (mapZ-1);
            
            vData.texcoords[tcCounter + 4] = (float)(x+1) / (mapX-1);
            vData.texcoords[tcCounter + 5] = (float)z / (mapZ-1);
            
            vData.texcoords[tcCounter + 6] = vData.texcoords[tcCounter + 4];
            vData.texcoords[tcCounter + 7] = vData.texcoords[tcCounter + 5];
            
            vData.texcoords[tcCounter + 8] = vData.texcoords[tcCounter + 2];
            vData.texcoords[tcCounter + 9] = vData.texcoords[tcCounter + 1];
            
            vData.texcoords[tcCounter + 10] = (float)(x+1) / (mapX-1);
            vData.texcoords[tcCounter + 11] = (float)(z+1) / (mapZ-1);
            tcCounter += 12;    // 6 texcoords, 12 floats
            
            // Fill normals array with data
            //--------------------------------------------------------------
            // TODO: Review normals calculation
            for (int i = 0; i < 18; i += 3)
            {
                vData.normals[nCounter + i] = 0.0f;
                vData.normals[nCounter + i + 1] = 1.0f;
                vData.normals[nCounter + i + 2] = 0.0f;
            }
            
            nCounter += 18;     // 6 vertex, 18 floats
            
            trisCounter += 2;
        }
    }
    
    // NOTE: At this point we have all vertex, texcoord, normal data for the model in vData struct

    Model model;

#ifdef USE_OPENGL_11
    model.data = vData;      // model data is vertex data  
#else   
    model.vaoId = rlglLoadModel(vData);     // Use loaded data to generate VAO

    // Now that vertex data is uploaded to GPU, we can free arrays
    free(vData.vertices);
    free(vData.texcoords);
    free(vData.normals);
#endif

    return model;
}

// Unload 3d model from memory
void UnloadModel(Model model)
{
#ifdef USE_OPENGL_11
    free(model.data.vertices);
    free(model.data.texcoords);
    free(model.data.normals);
#endif

#ifdef USE_OPENGL_33
    rlDeleteVertexArrays(model.vaoId);
#endif
}

// Draw a model
void DrawModel(Model model, Vector3 position, float scale, Color color)
{
    rlglDrawModel(model, false);
}

// Draw a textured model
void DrawModelEx(Model model, Texture2D texture, Vector3 position, float scale, Color tint)
{
    rlEnableTexture(texture.glId);
    
    DrawModel(model, position, scale, tint);
    
    rlDisableTexture();
}

// Draw a model wires
void DrawModelWires(Model model, Vector3 position, float scale, Color color)
{
    rlglDrawModel(model, true);
}

// Draw a billboard
void DrawBillboard(Camera camera, Texture2D texture, Vector3 center, float size, Color tint)
{
    // NOTE: Billboard size will maintain texture aspect ratio, size will be billboard width
    Vector2 sizeRatio = { size, size * (float)texture.height/texture.width };
    
    Matrix viewMatrix = MatrixLookAt(camera.position, camera.target, camera.up);
    MatrixTranspose(&viewMatrix);
    
    Vector3 right = { viewMatrix.m0, viewMatrix.m4, viewMatrix.m8 };
    Vector3 up = { viewMatrix.m1, viewMatrix.m5, viewMatrix.m9 };
/*    
    d-------c
    |       |
    |   *   |
    |       |
    a-------b
*/  
    VectorScale(&right, sizeRatio.x/2);
    VectorScale(&up, sizeRatio.y/2);
    
    Vector3 p1 = VectorAdd(right, up);
    Vector3 p2 = VectorSubtract(right, up);

    Vector3 a = VectorSubtract(center, p2);
    Vector3 b = VectorAdd(center, p1);
    Vector3 c = VectorAdd(center, p2);
    Vector3 d = VectorSubtract(center, p1);
    
    rlEnableTexture(texture.glId);
      
    rlBegin(RL_QUADS);
        rlColor4ub(tint.r, tint.g, tint.b, tint.a);
        rlNormal3f(0.0f, 1.0f, 0.0f); 
        rlTexCoord2f(0.0f, 0.0f); rlVertex3f(a.x, a.y, a.z);
        rlTexCoord2f(1.0f, 0.0f); rlVertex3f(b.x, b.y, b.z);
        rlTexCoord2f(1.0f, 1.0f); rlVertex3f(c.x, c.y, c.z);
        rlTexCoord2f(0.0f, 1.0f); rlVertex3f(d.x, d.y, d.z);
    rlEnd();
    
    rlDisableTexture();
}

// Draw a billboard (part of a texture defined by a rectangle)
void DrawBillboardRec(Camera camera, Texture2D texture, Rectangle sourceRec, Vector3 center, float size, Color tint)
{
    // NOTE: Billboard size will maintain sourceRec aspect ratio, size will represent billboard width
    Vector2 sizeRatio = { size, size * (float)sourceRec.height/sourceRec.width };

    Matrix viewMatrix = MatrixLookAt(camera.position, camera.target, camera.up);
    MatrixTranspose(&viewMatrix);
    
    Vector3 right = { viewMatrix.m0, viewMatrix.m4, viewMatrix.m8 };
    Vector3 up = { viewMatrix.m1, viewMatrix.m5, viewMatrix.m9 };
/*    
    d-------c
    |       |
    |   *   |
    |       |
    a-------b
*/  
    VectorScale(&right, sizeRatio.x/2);
    VectorScale(&up, sizeRatio.y/2);

    Vector3 p1 = VectorAdd(right, up);
    Vector3 p2 = VectorSubtract(right, up);

    Vector3 a = VectorSubtract(center, p2);
    Vector3 b = VectorAdd(center, p1);
    Vector3 c = VectorAdd(center, p2);
    Vector3 d = VectorSubtract(center, p1);
    
    rlEnableTexture(texture.glId);
    
    rlBegin(RL_QUADS);
        rlColor4ub(tint.r, tint.g, tint.b, tint.a);
        
        // Bottom-left corner for texture and quad
        rlTexCoord2f((float)sourceRec.x / texture.width, (float)sourceRec.y / texture.height); 
        rlVertex3f(a.x, a.y, a.z);
        
        // Bottom-right corner for texture and quad
        rlTexCoord2f((float)(sourceRec.x + sourceRec.width) / texture.width, (float)sourceRec.y / texture.height);
        rlVertex3f(b.x, b.y, b.z);
        
        // Top-right corner for texture and quad
        rlTexCoord2f((float)(sourceRec.x + sourceRec.width) / texture.width, (float)(sourceRec.y + sourceRec.height) / texture.height); 
        rlVertex3f(c.x, c.y, c.z);
        
        // Top-left corner for texture and quad
        rlTexCoord2f((float)sourceRec.x / texture.width, (float)(sourceRec.y + sourceRec.height) / texture.height);
        rlVertex3f(d.x, d.y, d.z);
    rlEnd();
    
    rlDisableTexture();
}

// Get current vertex y altitude (proportional to pixel colors in grayscale)
static float GetHeightValue(Color pixel)
{
    return (((float)pixel.r + (float)pixel.g + (float)pixel.b)/3);
}