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/sprite.vert

@@ -0,0 +1,21 @@
+#version 460
+// Particles: a camera-facing quad per sprite, from the vertex index (6 vertices, no buffer).
+#include "backend.glsl"
+PUSH_BLOCK {
+    mat4 viewProj;
+    vec4 posSize; // xyz centre, w half size
+    vec4 color;   // rgb (HDR: can be bright), a
+    vec4 right;   // camera right, w = rotation (radians)
+    vec4 up;      // camera up, w = texture index (bits)
+} pc;
+layout(location = 0) out vec2 v_uv;
+const vec2 kQuad[6] = vec2[](vec2(-1,-1), vec2(1,-1), vec2(1,1), vec2(-1,-1), vec2(1,1), vec2(-1,1));
+void main() {
+    vec2 q = kQuad[VERTEX_ID];
+    float c = cos(pc.right.w), s = sin(pc.right.w);
+    vec2 r = vec2(c * q.x - s * q.y, s * q.x + c * q.y);
+    vec3 world = pc.posSize.xyz + (pc.right.xyz * r.x + pc.up.xyz * r.y) * pc.posSize.w;
+    v_uv = q * 0.5 + 0.5;
+    v_uv.y = 1.0 - v_uv.y;
+    gl_Position = pc.viewProj * vec4(world, 1.0);
+}