Fry3DX 0.4: an easy 3D modeller

Shapes with live settings, shape editing, knife and hole tools, drawing
shapes onto other objects, combining objects (add / subtract / overlap),
copies, thickness, painting with stickers and layers, a Layout tab, a
Print tab with checks, packed .fry files with autosave, export to GLB,
glTF, FBX, OBJ, 3MF, STL and PLY, folders in Layers, its own crash
screen, and a website for GitHub Pages in docs/.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NMSrd5oe1GpUD7E6d825KP

engine/shaders/hzb.frag

@@ -0,0 +1,24 @@
+#version 460
+// The hierarchical Z-buffer's base: the scene's depth shrunk to a small grid, each texel the
+// farthest depth under it. The CPU reads it back and builds the rest of the pyramid (see
+// Renderer::occluded). Rows match the depth buffer's on both backends.
+#define KEEL_POST // screen-space: render targets, sampled clamped
+#include "backend.glsl"
+PUSH_BLOCK {
+    uint depth;      // texture slot of the scene's depth
+    uint srcW, srcH; // its size
+    uint dstW, dstH; // this grid's
+} pc;
+
+layout(location = 0) out vec4 o_depth;
+
+void main() {
+    ivec2 o = ivec2(gl_FragCoord.xy);
+    vec2 scale = vec2(pc.srcW, pc.srcH) / vec2(pc.dstW, pc.dstH);
+    ivec2 lo = ivec2(floor(vec2(o) * scale));
+    ivec2 hi = min(ivec2(ceil(vec2(o + 1) * scale)), ivec2(pc.srcW, pc.srcH));
+    float far = 0.0;
+    for (int y = lo.y; y < hi.y; ++y)
+        for (int x = lo.x; x < hi.x; ++x) far = max(far, fetchTex(pc.depth, ivec2(x, y)).r);
+    o_depth = vec4(far);
+}