raylib/examples/textures_particles_trail_blending.c

/*******************************************************************************************
*
*   raylib example - particles trail blending
*
*   This example has been created using raylib 1.3 (www.raylib.com)
*   raylib is licensed under an unmodified zlib/libpng license (View raylib.h for details)
*
*   Copyright (c) 2015 Ramon Santamaria (@raysan5)
*
********************************************************************************************/

#include "raylib.h"

#define MAX_PARTICLES 200

// Particle structure with basic data
typedef struct {
    Vector2 position;
    Color color;
    float alpha;
    float size;
    float rotation;
    bool active;        // NOTE: Use it to activate/deactive particle
} Particle;

int main()
{
    // Initialization
    //--------------------------------------------------------------------------------------
    int screenWidth = 800;
    int screenHeight = 450;

    InitWindow(screenWidth, screenHeight, "raylib [textures] example - particles trail blending");
    
    // Particles pool, reuse them!
    Particle mouseTail[MAX_PARTICLES]; 
    
    // Initialize particles
    for (int i = 0; i < MAX_PARTICLES; i++)
    {
        mouseTail[i].position = (Vector2){ 0, 0 };
        mouseTail[i].color = (Color){ GetRandomValue(0, 255), GetRandomValue(0, 255), GetRandomValue(0, 255), 255 };
        mouseTail[i].alpha = 1.0f;
        mouseTail[i].size = (float)GetRandomValue(1, 30)/20.0f;
        mouseTail[i].rotation = GetRandomValue(0, 360);
        mouseTail[i].active = false;
    }
    
    float gravity = 3.0f;

    Texture2D smoke = LoadTexture("resources/smoke.png");
    
    int blending = BLEND_ALPHA;
    
    SetTargetFPS(60);
    //--------------------------------------------------------------------------------------

    // Main game loop
    while (!WindowShouldClose())    // Detect window close button or ESC key
    {
        // Update
        //----------------------------------------------------------------------------------
        
        // Activate one particle every frame and Update active particles
        // NOTE: Particles initial position should be mouse position when activated
        // NOTE: Particles fall down with gravity and rotation... and disappear after 2 seconds (alpha = 0)
        // NOTE: When a particle disappears, active = false and it can be reused.
        for (int i = 0; i < MAX_PARTICLES; i++)
        {
            if (!mouseTail[i].active)
            {
                mouseTail[i].active = true;
                mouseTail[i].alpha = 1.0f;
                mouseTail[i].position = GetMousePosition();
                i = MAX_PARTICLES;
            }
        }

        for (int i = 0; i < MAX_PARTICLES; i++)
        {
            if (mouseTail[i].active)
            {
                mouseTail[i].position.y += gravity;
                mouseTail[i].alpha -= 0.01f;
                
                if (mouseTail[i].alpha <= 0.0f) mouseTail[i].active = false;
                
                mouseTail[i].rotation += 5.0f;
            }
        }
        
        if (IsKeyPressed(KEY_SPACE))
        {
            if (blending == BLEND_ALPHA) blending = BLEND_ADDITIVE;
            else blending = BLEND_ALPHA;
        }
        //----------------------------------------------------------------------------------

        // Draw
        //----------------------------------------------------------------------------------
        BeginDrawing();

            ClearBackground(DARKGRAY);
            
            BeginBlendMode(blending);

                // Draw active particles
                for (int i = 0; i < MAX_PARTICLES; i++)
                {
                    if (mouseTail[i].active) DrawTexturePro(smoke, (Rectangle){ 0, 0, smoke.width, smoke.height }, 
                                                           (Rectangle){ mouseTail[i].position.x, mouseTail[i].position.y, smoke.width*mouseTail[i].size, smoke.height*mouseTail[i].size },
                                                           (Vector2){ smoke.width*mouseTail[i].size/2, smoke.height*mouseTail[i].size/2 }, mouseTail[i].rotation,
                                                           Fade(mouseTail[i].color, mouseTail[i].alpha));
                }
            
            EndBlendMode();
            
            DrawText("PRESS SPACE to CHANGE BLENDING MODE", 180, 20, 20, BLACK);
            
            if (blending == BLEND_ALPHA) DrawText("ALPHA BLENDING", 290, screenHeight - 40, 20, BLACK);
            else DrawText("ADDITIVE BLENDING", 280, screenHeight - 40, 20, RAYWHITE);
            
        EndDrawing();
        //----------------------------------------------------------------------------------
    }

    // De-Initialization
    //--------------------------------------------------------------------------------------
    UnloadTexture(smoke);
    
    CloseWindow();        // Close window and OpenGL context
    //--------------------------------------------------------------------------------------

    return 0;
}