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#version 430 core
#define M_PI 3.14159265358979323846
layout (local_size_x = 1) in;
struct Vertex {
vec3 pos;
vec3 norm;
vec2 uv;
};
layout(std430, binding=0) readonly buffer Vertices {
Vertex vertices[];
};
layout(std430, binding=1) readonly buffer VertexIndices {
unsigned int indices[];
};
layout(std430, binding=2) readonly buffer VertexOffsets {
unsigned int offsets[];
};
layout(std430, binding=3) writeonly buffer Output {
Vertex new_vertices[];
};
void main(){
unsigned int size = offsets[gl_GlobalInvocationID.x + 1] - offsets[gl_GlobalInvocationID.x];
new_vertices[gl_GlobalInvocationID.x].uv = vec2(0.0f, 0.0f);
// FIXME: size or size - 1?
float t = 3.0f/8.0f + 2.0f/8.0f * cos(2.0f * M_PI / (float(size) - 1.0f));
float alpha = 5.0f/8.0f - t * t;
vec3 pos = vec3(0.0f, 0.0f, 0.0f);
vec3 norm = vec3(0.0f, 0.0f, 0.0f);
for (unsigned int i = 1; i < size; i++) {
pos += vertices[indices[offsets[gl_GlobalInvocationID.x] + i]].pos;
norm += vertices[indices[offsets[gl_GlobalInvocationID.x] + i]].norm;
}
new_vertices[gl_GlobalInvocationID.x].pos = (1.0f - alpha) * vertices[indices[offsets[gl_GlobalInvocationID.x]]].pos + alpha / (float(size) - 1.0f) * pos;
new_vertices[gl_GlobalInvocationID.x].norm = normalize((1.0f - alpha) * vertices[indices[offsets[gl_GlobalInvocationID.x]]].norm + alpha / (float(size) - 1.0f) * norm);
}