Lecture 13: Global Illumination & Path Tracing (24)
adam2451
Given this picture why would we ever choose to sample the hemisphere uniformly over the sampling points on lights. Is there a speed trade off? Does sampling points on light always perform better? Or is this just due to the type of imagery we are modeling here?
jayc809
[deleted]
jayc809
@adam2451 I think there is definitely a trade-off between sampling uniform hemisphere versus light. I think the computation needed for light sampling increases at a higher exponential rate when the lighting complexity of the scene increases when compared to hemisphere sampling. Moreover, global illumination, where light bounces off different surfaces prior to the point to be rendered, might also be easier to implement for hemisphere sampling.
lycorisradiatu
I wonder in what situation would we choose one over the other. Is there any specific example scenarios?
misha-wu
Why does this picture create noise in the grey areas when sampled uniformly?
myxamediyar
To answer misha, my understanding is that not all screen to world points cast a ray in the direction of the light source, because it is uniform sampling. So chances are that it won't hit the light source and thus we would color it dark.
Zzz212zzZ
I think the noise is caused by fewer light rays captured by the camera. The uniform sampling doesn't have an emphasis on which area is more likely to have more rays passed by.
aidangarde
In what situations is hemisphere more differentiable from light sampling? It seems that even in a one-source fairly simple image, the hemisphere loses a ton of quality. However, it seems that the hemisphere is computationally way cheaper to use hemisphere lighting. My guess is on textures in smaller areas that don't require as much attention, hemisphere is fine, but for any major rendering, light sampling is essential.
Given this picture why would we ever choose to sample the hemisphere uniformly over the sampling points on lights. Is there a speed trade off? Does sampling points on light always perform better? Or is this just due to the type of imagery we are modeling here?
[deleted]
@adam2451 I think there is definitely a trade-off between sampling uniform hemisphere versus light. I think the computation needed for light sampling increases at a higher exponential rate when the lighting complexity of the scene increases when compared to hemisphere sampling. Moreover, global illumination, where light bounces off different surfaces prior to the point to be rendered, might also be easier to implement for hemisphere sampling.
I wonder in what situation would we choose one over the other. Is there any specific example scenarios?
Why does this picture create noise in the grey areas when sampled uniformly?
To answer misha, my understanding is that not all screen to world points cast a ray in the direction of the light source, because it is uniform sampling. So chances are that it won't hit the light source and thus we would color it dark.
I think the noise is caused by fewer light rays captured by the camera. The uniform sampling doesn't have an emphasis on which area is more likely to have more rays passed by.
In what situations is hemisphere more differentiable from light sampling? It seems that even in a one-source fairly simple image, the hemisphere loses a ton of quality. However, it seems that the hemisphere is computationally way cheaper to use hemisphere lighting. My guess is on textures in smaller areas that don't require as much attention, hemisphere is fine, but for any major rendering, light sampling is essential.