From 9174f1ec0b0055b02e73eeea64634a9025d0ab0c Mon Sep 17 00:00:00 2001
From: Modin Modin <ua.modin@gmail.com>
Date: Mon, 6 Apr 2026 19:22:35 -0400
Subject: [PATCH] Sample 3

---
 strand.comp | 71 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 71 insertions(+)
 create mode 100644 strand.comp

diff --git a/strand.comp b/strand.comp
new file mode 100644
index 0000000..310da9b
--- /dev/null
+++ b/strand.comp
@@ -0,0 +1,71 @@
+#version 460
+#extension GL_EXT_debug_printf : enable
+#extension GL_EXT_shader_atomic_float : enable
+
+layout(local_size_x = 64) in; 
+
+struct CurveHeader {
+    uint poolOffset;
+    uint pointCount;
+    uint maxPoints;
+    uint _padding;
+    vec4 color;
+};
+
+struct PointData {
+    vec4 pos; // xyz = worldPos, w = radius
+};
+
+layout(std430, binding = 0) readonly buffer HeaderBuffer { CurveHeader headers[]; };
+layout(std430, binding = 1) readonly buffer PointPool    { PointData pool[]; };
+layout(std430, binding = 2) writeonly buffer RenderBuffer { vec4 smoothPoints[]; };
+layout(r32f, binding = 3) uniform image3D shadowVolume;
+
+layout(push_constant) uniform Push {
+    mat4 viewProj;
+    vec3 gridOrigin;
+    float gridCellSize;
+    float gridExtent;
+    uint frameCount;
+    float _pad[2];
+} pc;
+
+shared vec4 s_Points[100];
+shared CurveHeader s_Header;
+
+void main() {
+    uint strandIdx = gl_WorkGroupID.x;
+    uint segmentIdx = gl_LocalInvocationID.x; // 0 to 63
+    
+    if (segmentIdx == 0) s_Header = headers[strandIdx];
+    barrier();
+
+    if (s_Header.pointCount == 0) return;
+
+    for (uint i = segmentIdx; i < 100; i += 64) {
+        if (i < s_Header.pointCount) {
+            s_Points[i] = pool[s_Header.poolOffset + i].pos;
+        }
+    }
+    barrier();
+
+    float t_global = float(segmentIdx) / 63.0;
+    float segProgress = t_global * float(s_Header.pointCount - 1);
+    int i = int(floor(segProgress));
+    float t_local = fract(segProgress);
+
+    // Fetch from shared memory
+    vec3 p0 = s_Points[max(i - 1, 0)].xyz;
+    vec3 p1 = s_Points[i].xyz;
+    vec3 p2 = s_Points[min(i + 1, int(s_Header.pointCount - 1))].xyz;
+    vec3 p3 = s_Points[min(i + 2, int(s_Header.pointCount - 1))].xyz;
+
+    vec3 finalPos = catmullRom(p0, p1, p2, p3, t_local);
+    float radius = mix(s_Points[i].w, s_Points[min(i + 1, int(s_Header.pointCount - 1))].w, t_local);
+    uint outIdx = (strandIdx * 64) + segmentIdx;
+    smoothPoints[outIdx] = vec4(finalPos, radius);
+	ivec3 voxel = ivec3(((finalPos - pc.gridOrigin) / pc.gridExtent)*pc.gridSize);
+	if (all(greaterThanEqual(voxel, ivec3(0))) && all(lessThan(voxel, ivec3(pc.gridSize)))) {
+		imageAtomicAdd(shadowVolume, voxel, 0.01); 
+	}
+}