docs: Update tech doc with Renderer3D initialization fix

Document the additional fix required for effects with Renderer3D members.
Explains why initialized_ flag is needed instead of ctx_.device check.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/doc/AUXILIARY_TEXTURE_INIT.md b/doc/AUXILIARY_TEXTURE_INIT.md
index e4200d1..d78c5ae 100644
--- a/doc/AUXILIARY_TEXTURE_INIT.md
+++ b/doc/AUXILIARY_TEXTURE_INIT.md
@@ -153,6 +153,28 @@ All 36 tests pass. Verified:
 - No artifacts or half-resolution bugs
 - Window resize works correctly
 
+## Additional Fix Required
+
+After swapping init/resize order, effects with Renderer3D (FlashCubeEffect, Hybrid3DEffect) crashed when resize() tried to use uninitialized renderer.
+
+**Solution:** Add `initialized_` flag to track if init() was called.
+
+```cpp
+// In header
+bool initialized_ = false;
+
+// In init()
+renderer_.init(ctx_.device, ctx_.queue, ctx_.format);
+renderer_.resize(width_, height_);
+initialized_ = true;  // Mark as initialized
+
+// In resize()
+if (!initialized_)
+  return;  // Early exit if not initialized yet
+```
+
+**Why not check `ctx_.device`?** Device exists before init() (passed to constructor), but Renderer3D not initialized yet.
+
 ## Related Documentation
 
 - `doc/MASKING_SYSTEM.md` - Auxiliary texture usage patterns