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#version 330
#if defined VERTEX_SHADER
uniform ivec3 voxel_size;
void main() {
int x = gl_VertexID % voxel_size.x;
int y = (gl_VertexID / voxel_size.y) % voxel_size.y;
int z = gl_VertexID / (voxel_size.x * voxel_size.y);
gl_Position = vec4(float(x), float(y), float(z), 0.0);
}
#elif defined GEOMETRY_SHADER
layout(points) in;
layout(points, max_vertices = 1) out;
uniform sampler2D lookup;
uniform ivec3 voxel_size;
out vec3 pos;
float lookup_3d(ivec3 p) {
int x = (p.z * voxel_size.x) % 1000 + p.x % voxel_size.x;
int y = (p.z / 10) * voxel_size.x + p.y;
return texelFetch(lookup, ivec2(x, y), 0).r;
}
void main() {
ivec3 p = ivec3(gl_in[0].gl_Position.xyz);
float alive = lookup_3d(p);
// Read all the neighbor cubes
int neighbours = 0;
if(lookup_3d(p + ivec3(0, 1, 0)) > 0) neighbours++;
if(lookup_3d(p + ivec3(0, -1, 0)) > 0) neighbours++;
if(lookup_3d(p + ivec3(-1, 0, 0)) > 0) neighbours++;
if(lookup_3d(p + ivec3(1, 0, 0)) > 0) neighbours++;
if(lookup_3d(p + ivec3(0, 0, 1)) > 0) neighbours++;
if(lookup_3d(p + ivec3(0, 0, -1)) > 0) neighbours++;
if (alive > 0) {
// If we're at the voxel edge we should always render the cube
if (p.x == 0 || p.x == 99) neighbours = 0;
if (p.y == 0 || p.y == 99) neighbours = 0;
if (p.z == 0 || p.z == 99) neighbours = 0;
if (neighbours < 6) {
pos = gl_in[0].gl_Position.xyz;
EmitVertex();
}
}
}
#endif
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