3
votes
Accepted
Plotting pbrt-v3 Gaussian filter
You probably want to set sigma to be a fraction of the radius, rather than a fixed value. Sigma controls the actual shape of the filter, while radius just controls how far out the filter gets cut off (...
- 24.8k
2
votes
Accepted
How to change a RGB value using a radiance value?
What you're looking for is called tone mapping, which is the process of mapping from HDR color values generated by a physically based renderer, to LDR color values suitable for display on a screen. It ...
- 24.8k
2
votes
Accepted
Confusion about PDF defined in solid angle / area measure
Actually,shape->Sample(ref, u, pdf) returns the pdf in solid angle measure.The sample function in sample is actually this.
...
- 36
2
votes
Conflicting definitions for the distribution of normals $D$ in microfacet BSDFs
The units of the NDF are tricky. For whatever it's worth, Heitz's convention of defining it relative to a 1 m² reference geometric surface is unusual, and although I can see why he would want to ...
- 24.8k
1
vote
Confusion regarding incident direction in render equation
$L_i(p,\omega_i) = L_o(p+t\omega_i,-\omega_i)$ where t is some distance to another point, so $\omega_i$ is "positive" (-) when evaluating $L_o$ but "negative" (+) for $L_i$. So if $...
- 129
1
vote
Accepted
How is the maximum value for alpha (roughness == 1) decided for microfacet models?
In truth, there is no mathematical maximum value for $\alpha$. As you noted, microfacet slope is unbounded, so in principle you could have arbitrarily large slope values and hence arbitrarily large $\...
- 24.8k
1
vote
Accepted
Is spectral response curve and spectral power distribution the same thing?
The book distinguishes a spectral power distribution from a spectral response curve because they are not the same, they are adjoint.
The thing about adjoints that makes them a little tricky to wrap ...
- 771
1
vote
Accepted
How can I account for specular interactions in shadow rays?
Shadow rays that hit a glass surface or similar are stopped because there's no direct path from the light source to the shading point—there's a piece of glass in the way.
for perfectly specular ...
- 24.8k
1
vote
Accepted
How to decide which child of BVH to visit based on sign of ray's direction vector?
In your example of a BVH cell partitioned along the x axis, if the ray is going left to right (increasing x), then the cell with the lower x comes first; but if it's going right to left (decreasing x),...
- 24.8k
1
vote
Accepted
How to calculate the PDF of a multi-lobe BSDF
The summation doesn't include the BxDF that was picked for sampling. Look again at this line:
if (bxdfs[i] != bxdf && bxdfs[i]->MatchesFlags(type))
...
- 24.8k
Only top scored, non community-wiki answers of a minimum length are eligible