Module rendering/post-processing/mega/shader.glsl

Mega-shader: single-pass post-processing fragment shader.

Fuses chromatic lens distortion, detector noise, EOG, tone mapping, and vignette into one fullscreen pass. Each effect is gated behind an #ifdef USE_* define so a recompile is needed only when an effect is toggled on/off — value tweaks just update uniforms.

Pre-stages owned by the host:

• Bloom pyramid renders into uBloomTexture (see BloomChain). The mega-shader samples bloom at the SAME (chromatic-aberrated) UVs as the scene so bloom is effectively additively-blended into the HDR buffer BEFORE chromatic lens distortion samples from it.
• FXAA is a separate post-pass after the mega-shader, since edge detection needs neighbor reads of the final LDR pixels.

Operation order:

1. Bloom additively mixed into the HDR scene (per-channel at distorted UVs when lens distortion is on)
2. Lens distortion (sampling lookup)
3. Detector noise
4. EOG (Exposure-Offset-Gamma)
5. Tone mapping (mode-switched via LUXAR_TONE_MAPPING_MODE shader-define; values are Luxar-internal IDs 1..6, NOT THREE's enum values — see toneMappingModeDefine in the material file for the mapping. NoToneMapping aliases to Linear so it clamps to [0,1].)
6. Vignette
7. sRGB encoding (final write; matches outputColorSpace = sRGB)