Circuit & ShaderNova
Circuit
Hey ShaderNova, I’ve been trying to squeeze a realistic refraction effect into a 2 ms frame budget on mobile GPUs, but the traditional dielectric approximation just kills performance. Think you can help me craft a more efficient shader that still looks like true glass?
ShaderNova
Don’t over‑engineer it, just cut the noise. Keep a single texel offset, clamp the refracted UV to the viewport, and drop the Schlick mix for a fixed IOR. Sample once, then lerp the result with a tiny blur if you need softness. Here’s a bare‑bones sketch – no fences, just the idea:
```glsl
vec3 viewDir = normalize(vWorldPos - cameraPos);
vec3 refractDir = refract(viewDir, vNormal, 1.0/IOR);
vec2 offset = refractDir.xy * maxUV; // maxUV is viewport size in texels
vec2 uv = vUV + offset / texSize; // one‑pass lookup
vec4 refraction = texture(refractionTex, uv);
fragColor = mix(color, refraction, roughness);
```
Just that. If you still hit 2 ms, drop the `roughness` modulation, or replace the texture lookup with a low‑res blurred buffer. Performance is a poem of minimalism – every sample counts.
Circuit
Sounds solid, but be careful with the UV clamp—if the offset pushes past the edge, you’ll see hard edges or black bleed. You could wrap or use `clamp(uv, 0.0, 1.0)` after the addition. Also, the `mix` with roughness will add another branch; if you’re fighting 2 ms, hard‑code the blend factor or use a lookup table. Keep it tight.
ShaderNova
Right, clamp the UV back to [0,1] so you don’t end up with a black hole at the edges. And yeah, ditch that `mix` branch – hard‑code the blend, or pull the value from a tiny 1×1 texel that stores the constant. The fewer branches, the fewer pipeline stalls. Trust me, a 2 ms window is a razor, not a playground.
Circuit
Got it, clamp and hard‑code that blend. Let’s push it to 2 ms and see if the GPU still loves it. Good luck.
ShaderNova
Good luck, and watch that frame budget. Don’t forget to profile after each tweak – the only way to win 2 ms is to keep the shader as light as a single ray of light. Happy hacking.