2 files changed, 67 insertions, 8 deletions

diff --git a/CONTEXT.md b/CONTEXT.md
index a490403..669c1fb 100644
--- a/CONTEXT.md
+++ b/CONTEXT.md
@@ -364,8 +364,13 @@ vocabulary / decisions.
   the INI). Not `sv_skyname`: that did not take effect at runtime in this
   build, so the skybox card now works on materials instead.
 - PNG is decoded with libpng16's simplified API (`dlopen`ed, no link
-  dependency); the RGBA pixels become an `ITexture` via
-  `IMaterialSystem::CreateTextureFromBits` (RGBA8888, one mip).
+  dependency). This build's `IMaterialSystem` interface ends at
+  `GetDisplayDeviceName` (the slots after it belong to `CMaterialSystem`
+  itself), so there is **no `CreateTextureFromBits`**. The pixels are uploaded
+  through `CreateProceduralTexture` (vtable 81) + an `ITextureRegenerator`
+  (`SetTextureRegenerator` 12, `Download` 13), which fills mip 0 through
+  `IVTFTexture::ImageData(frame,face,mip)` (39). `IVTFTexture`'s virtual
+  destructor occupies two slots, so Width=15, Height=16, RowSizeInBytes=19.
 - The texture is assigned with `IMaterialVar::SetTextureValue` to
   `$basetexture`, plus `$hdrbasetexture` / `$hdrcompressedtexture` when those
   vars exist, on every material in the `SkyBox textures` group or named
diff --git a/src/world.cpp b/src/world.cpp
index cf85795..391ab1a 100644
--- a/src/world.cpp
+++ b/src/world.cpp
@@ -409,6 +409,49 @@ bool load_png_rgba(const char *path, std::vector<unsigned char> &pixels,
   return true;
 }
 
+std::vector<unsigned char> g_sky_pixels;
+int g_sky_px_w = 0, g_sky_px_h = 0;
+
+// ITextureRegenerator has two virtuals: RegenerateTextureBits then Release.
+// This build has no IMaterialSystem::CreateTextureFromBits (its interface stops
+// at GetDisplayDeviceName), so the pixels are uploaded through a procedural
+// texture + regenerator instead.
+class SkyRegenerator {
+public:
+  virtual void RegenerateTextureBits(void *texture, void *vtf, void *rect) {
+    (void)texture;
+    (void)rect;
+    if (!vtf || g_sky_pixels.empty())
+      return;
+    using IntFn = int (*)(void *);
+    using PitchFn = int (*)(void *, int);
+    using DataFn = unsigned char *(*)(void *, int, int, int);
+    // IVTFTexture vtable: dtor takes 2 slots, then Init, so Width=15,
+    // Height=16, RowSizeInBytes=19, ImageData(frame,face,mip)=39.
+    int w = vfunc<IntFn>(vtf, 15)(vtf);            // IVTFTexture::Width
+    int h = vfunc<IntFn>(vtf, 16)(vtf);            // IVTFTexture::Height
+    if (w <= 0 || h <= 0)
+      return;
+    int pitch = vfunc<PitchFn>(vtf, 19)(vtf, 0);   // RowSizeInBytes(0)
+    unsigned char *dst = vfunc<DataFn>(vtf, 39)(vtf, 0, 0, 0); // ImageData
+    if (!dst || pitch <= 0)
+      return;
+    int rows = h < g_sky_px_h ? h : g_sky_px_h;
+    int src_stride = g_sky_px_w * 4;
+    int copy = w * 4;
+    if (copy > src_stride)
+      copy = src_stride;
+    for (int y = 0; y < rows; y++) {
+      const unsigned char *src =
+          g_sky_pixels.data() + (size_t)y * (size_t)src_stride;
+      memcpy(dst + (size_t)y * (size_t)pitch, src, (size_t)copy);
+    }
+  }
+  virtual void Release() {}
+};
+
+SkyRegenerator g_sky_regenerator;
+
 void *g_sky_tex = nullptr;
 bool g_sky_tex_tried = false;
 bool g_sky_applied = false;
@@ -573,16 +616,27 @@ void load_sky_texture() {
     }
     return;
   }
-  using CreateTexFn = void *(*)(void *, int, int, int, int, int,
-                                unsigned char *);
-  g_sky_tex = vfunc<CreateTexFn>(ms, 134)(ms, w, h, 1, 0 /* RGBA8888 */,
-                                          (int)pixels.size(), pixels.data());
+  g_sky_pixels.swap(pixels);
+  g_sky_px_w = w;
+  g_sky_px_h = h;
+
+  // The procedural texture keeps its own copy through the regenerator, which
+  // is called on Download() and again on device restore.
+  using CreateProcFn = void *(*)(void *, const char *, const char *, int, int,
+                                 int, int);
+  g_sky_tex = vfunc<CreateProcFn>(ms, 81)(
+      ms, "hl2hake/skybox", GROUP_SKYBOX, w, h, 0 /* RGBA8888 */,
+      0x10C /* CLAMPS|CLAMPT|NOMIP */);
   if (!g_sky_tex) {
-    logf("skybox: CreateTextureFromBits failed for %dx%d", w, h);
+    logf("skybox: CreateProceduralTexture failed for %dx%d", w, h);
     return;
   }
+  using SetRegenFn = void (*)(void *, void *);
+  using DownloadFn = void (*)(void *, void *, int);
+  vfunc<SetRegenFn>(g_sky_tex, 12)(g_sky_tex, &g_sky_regenerator);
+  vfunc<DownloadFn>(g_sky_tex, 13)(g_sky_tex, nullptr, 0);
   g_sky_fail_logged = false;
-  logf("skybox: image %s (%dx%d) loaded", path, w, h);
+  logf("skybox: image %s (%dx%d) uploaded", path, w, h);
 }
 
 } // namespace