BRDF
- Bidirectional reflectance distribution function
BRDF Texture
- BRDF Fake라고도 함.
half u = dot(L, N) * 0.5 + 0.5;
half v = dot(V, N);
half3 brdfTex = SAMPLE_TEXTURE2D(_BrdfTex, sampler_BrdfTex, half2(u, v)).rgb;
TODO - Ambient BRDF
- Gotanda 2010
| x | dot(V, N) |
| y | Shininess |
TODO - Environment IBL Map
- Schlick's approximation // fresnel
- Lazarov 2013
| x | dot(V, N) // cosθv |
| y | Roughness |
DFG LUT
| DFG | |
|---|---|
| D | Distrubution |
| F | Fresnel |
| G | Geometry |
예
Color c = diffuse * intensity + fresnelReflectionColor * fresnelTerm + translucentColor * t + Color(0, 0 ,0, specular);
c *= intensity;
half u = dot(L, N) * 0.5 + 0.5;
half v = dot(H, N);
half3 brdfTex = SAMPLE_TEXTURE2D(_BrdfTex, sampler_BrdfTex, half2(u, v)).rgb;
half3 color = albedo * (brdfTex.rgb + gloss * brdfTex.a) * 2;
// +--- B ---+ A : 빛과 마주치는 면
// | | B : 빛과 반대방향의 면
// D C C : 카메라와 마주치는 면
// | | D : 카메라와 90도 되는 면
// +--- A ---+
OffsetU // [-1, 1]
OffsetV // [-1, 1]
half2 brdfUV = float2(saturate(NdotV + OffsetU), saturate((LdotN + 1) * 0.5) + OffsetV);
brdfUV.y = 1 - brdfUV.y;
half3 brdfTex = tex2D(BRDFSampler, brdfUV).rgb;
half3 color = ambient + brdfTex;
Ref
- SIGGRAH 2013 Real Shading in Unreal Engine 4
- https://learnopengl.com/PBR/IBL/Specular-IBL
- SIGGRAH2019 - A Journey Through Implementing Multiscattering BRDFs and Area Lights
- https://teodutra.com/unity/shaders/cook-torrance/lookup-texture/2019/03/28/Lookup-The-Cook-Torrance/
- SIGGRAH2017 - Physically-Based Materials: Where Are We?
- Multi-Textured BRDF-based Lighting - Chris Wynn
- http://www.mentalwarp.com/~brice/brdf.php
- http://wiki.polycount.com/wiki/BDRF_map
- Stoyan Dimitrov: How Space Ape uses Uber Shaders in Unity for Mobile Games