ADD: HQ particles

shaders/particles_build_indices.comp

@@ -0,0 +1,46 @@
+#version 450
+
+// Output is a global indices[] buffer, indexed by gl_InstanceIndex.
+
+layout(local_size_x = 256, local_size_y = 1, local_size_z = 1) in;
+
+layout(std430, set = 0, binding = 0) readonly buffer SortedBlocks
+{
+    uint blocks[];
+} sortedBlocks;
+
+layout(std430, set = 0, binding = 1) writeonly buffer DrawIndices
+{
+    uint indices[];
+} outIndices;
+
+layout(push_constant) uniform Push
+{
+    uvec4 header; // x=base, y=count, z=flags (bit0=identity)
+} pc;
+
+const uint BLOCK_SIZE = 256u;
+
+void main()
+{
+    uint i = gl_GlobalInvocationID.x;
+    uint count = pc.header.y;
+    if (i >= count) return;
+
+    uint base = pc.header.x;
+    uint flags = pc.header.z;
+
+    uint outIdx = base + i;
+    uint particleIdx = base + i;
+
+    if ((flags & 1u) == 0u)
+    {
+        uint blockRank = i / BLOCK_SIZE;
+        uint within = i - blockRank * BLOCK_SIZE;
+        uint block = sortedBlocks.blocks[blockRank];
+        particleIdx = base + block * BLOCK_SIZE + within;
+    }
+
+    outIndices.indices[outIdx] = particleIdx;
+}
+