Ground truth option

생각 보다 배울게 많은 소스이다

mat3 t2w = BasisFrisvad(s.n);
mat3 w2t = transpose(t2w);

저기서 FrisVad는 아래서 나왔다

"Building an Orthonormal Basis from a 3D Unit Vector Without Normalization"

Finding an orthonormal basis from a unit 3D vector.

abstract 내용에 따르면 fewer arithmetic operations

http://orbit.dtu.dk/fedora/objects/orbit:113874/datastreams/file_10189336/content

소스 gist는 아래에

https://gist.github.com/XProger/b338c55634f1856d93030cd4f7964a5d

SphQuad squad = SphQuadInit(u_quadPoints[0].xyz, ex, ey, s.p);

위의 SphQuad도 검색하면 논문이 나온다

"An Area-Preserving Parametrization for Spherical Rectangles"

https://www.solidangle.com/research/egsr2013_spherical_rectangle.pdf

In particular, this is the case of numerical computation of radiance directly reflected (or scattered) from a point due to illumination from a planar rectangular light source, a common task in realistic rendering systems.

이걸 어찌 쓰나했는데 planar rect에 넣는 용이라 되어있다

SphQuad squad = SphQuadInit(uQuadPoints[0].xyz, ex, ey, position);
vec3 lightPos = SphQuadSample(squad, u1, u2);

MIS 코드

https://www.slideshare.net/takahiroharada/introduction-to-bidirectional-path-tracing-bdpt-implementation-using-opencl-cedec-2015

https://computergraphics.stackexchange.com/questions/215/multiple-importance-sampling-with-more-than-one-light

https://www.shadertoy.com/view/lsV3zV#