Participating media with three phase functions: isotropic (left), Heyney-Greenstein (middle), and Rayleigh (right).
This project shows different forms of participating media, including fog using three phase functions (isotropic, Heyney-Greenstein, and Rayleigh) as well as subsurface scattering. For these images, I used my adjoint photons from Project 15 and implemented scattering as a probabilistic function. The energies of the scattered rays are modulated by the specified phase function and use an extinction coefficient of 1.0e-3. The Rayleigh scattering favors blue photons more than the rest because it uses a scattering probability based on 1/lambda^4. Unfortunately, though the Raleigh phase function and scattering are shown for the Cornell Box, I did not have a chance to try the code on an actual outdoor scene where the blueness would be more apparent, due to time constraints.
As always, the images are tone-mapped using clamping and gamma corrected. For some reason, some pixels seem especially bright, causing the images to appear noisier than normal. This may be a bug in my adjoint photons code with importance sampling, though it seems to be greatly reduced if I let the simulation run for a long time. As always, the images are tone-mapped using clamping and gamma corrected.
Participating media with three phase functions: isotropic (left), Heyney-Greenstein (middle), and Rayleigh (right).
The cornell box with adjoint photons (left) and with subsurface scattering in the boxes with an isotropic phase function (right). The right image was given more compute time so it converged more than the left.