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/asset/ksky.h

@@ -0,0 +1,25 @@
+#pragma once
+// .ksky: a sky for the renderer, compiled by assetc from an equirectangular .hdr.
+//   KskyHeader
+//   `levels` images of width >> k × height >> k RGBM8 pixels (rows top-down), largest first
+// Directions are world space (+Z up): u = atan2(d.y, d.x) / 2π + 0.5, v = acos(d.z) / π.
+// A pixel's linear radiance is rgb · a · kSkyRange. The sky is normalised so its upper half
+// averages 1 (the engine scales it by the map's sky intensity), and the sun is taken out of
+// it (the engine draws its own, matching the shadows). Level k is the sky as a surface of
+// roughness k / (levels - 1) reflects it (GGX prefiltered), for image-based reflections.
+#include <cstdint>
+
+namespace keel {
+
+inline constexpr uint32_t kKskyVersion = 1;
+inline constexpr float kSkyRange = 16.0f;
+
+struct KskyHeader {
+    char magic[4]; // "KSKY"
+    uint32_t version;
+    uint32_t width, height, levels;
+    float sunDir[3]; // towards where the sun was in the photo
+    float sh[27];    // 9 RGB spherical harmonics of the light it casts: Σ shᵢ·Yᵢ(n) = irradiance / π
+};
+
+} // namespace keel