bgfx/examples/48-drawindirect/cs_drawindirect.sc

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/*
* Copyright 2022 Liam Twigger. All rights reserved.
* License: https://github.com/bkaradzic/bgfx/blob/master/LICENSE
*/
#include "bgfx_compute.sh"
//instance data for all instances (pre culling)
BUFFER_RO(instanceDataIn, vec4, 0);
// Output
BUFFER_WR(indirectBuffer, uvec4, 1);
BUFFER_WR(instanceBufferOut, vec4, 2);
#ifdef INDIRECT_COUNT
BUFFER_WR(indirectCountBuffer, int, 3);
#endif
uniform vec4 u_drawParams;
// Use 64*1*1 local threads
NUM_THREADS(64, 1, 1)
void main()
{
int tId = int(gl_GlobalInvocationID.x);
int numDrawItems = int(u_drawParams.x);
int sideSize = int(u_drawParams.y);
float time = u_drawParams.z;
// Work out the amount of work we're going to do here
int maxToDraw = min(sideSize*sideSize, numDrawItems);
int numToDrawPerThread = maxToDraw/64 + 1;
int idxStart = tId*numToDrawPerThread;
int idxMax = min(maxToDraw, (tId+1)*numToDrawPerThread);
// Prepare draw mtx
for (int k = idxStart; k < idxMax; k++) {
int yy = k / sideSize;
int xx = k % sideSize;
float _ax = time + xx * 0.21f;
float _ay = time + yy * 0.37f;
float sx = sin(_ax);
float cx = cos(_ax);
float sy = sin(_ay);
float cy = cos(_ay);
vec4 a = vec4( cy, 0, sy, 0);
vec4 b = vec4( sx*sy, cx, -sx*cy, 0);
vec4 c = vec4(-cx*sy, sx, cx*cy, 0);
vec4 d = vec4(-15.0f - (sideSize-11)*1.2f + float(xx) * 3.0f, -15.0f - (sideSize-11)*1.4f + float(yy) * 3.0f, max(0.0f, (sideSize-11.0f)*3.0f), 1.0f);
vec4 color;
color.x = sin(time + float(xx) / 11.0f) * 0.5f + 0.5f;
color.y = cos(time + float(yy) / 11.0f) * 0.5f + 0.5f;
color.z = sin(time * 3.0f) * 0.5f + 0.5f;
color.w = 1.0f;
instanceBufferOut[k*5+0] = a;
instanceBufferOut[k*5+1] = b;
instanceBufferOut[k*5+2] = c;
instanceBufferOut[k*5+3] = d;
instanceBufferOut[k*5+4] = color;
}
// Fill indirect buffer
for (int k = idxStart; k < idxMax; k++) {
drawIndexedIndirect(
// Target location params:
indirectBuffer, // target buffer
k, // index in buffer
// Draw call params:
instanceDataIn[k].w, // number of indices for this draw call
1u, // number of instances for this draw call. You can disable this draw call by setting to zero
instanceDataIn[k].z, // offset in the index buffer
instanceDataIn[k].x, // offset in the vertex buffer. Note that you can use this to "reindex" submeshses - all indicies in this draw will be decremented by this amount
k // offset in the instance buffer. If you are drawing more than 1 instance per call see gpudrivenrendering for how to handle
);
}
#ifdef INDIRECT_COUNT
if (tId == 0)
{
// If BGFX_CAPS_DRAW_INDIRECT_COUNT is supported, you can limit the
// number of draw calls dynamically without a CPU round trip
indirectCountBuffer[0] = maxToDraw;
}
#endif
}