OllieBrown

With the end of GSoC approaching I want to take inventory of what has been achieved so far. To reiterate I do fully intend to stick with this and keep improving lighter2, assuming I have not overstayed my welcome.

Here's some results. I've spent today rendering images so that I can show what I can achieve with my photon mapper when I hold it's hand and try my best to get good results.

First up, an image of the Cornell Box with just basic raytracing. This scene was rendered with global ambient turned off, all lights forced to realistic attenuation and all light power scaled by 8.0, as such:

lighter2 --directlight=raytracer --noglobalambient --forcerealistic --lmdensity=20.0 --lightpowerscale=8.0 data/NewCornell

This image uses light maps with direct light only computed with raytracing. Note the dark shadows and the relatively small amount of light on the ceiling.

Next, an image of the Cornell Box with just Photon Mapping (for both direct and indirect light). Here we shot 5M photons and sampled 5K times for each density estimation. The command line was like such:

lighter2 --directlight=photonmapper --indirectlight=photonmapper --numphotons=5000000 --maxdensitysamples=5000 --sampledistance=20.0 --nofinalgather --lmdensity=20.0 --pmlightscale=100.0 data/NewCornell

This image shows the results of lighter2 photon mapping only. The image captures all of the major features of the raytraced image (shadows, shapes of light attenuation) but it also captures some indirect light (though not yet with color). The shadows and ceiling are brighter in this image than in the raytraced image. Unfortunately, the noise is still too high but better than it has been all summer.

Lastly, an image of the Cornell Box with direct light done with raytracing and indirect light with photon mapping. It was VERY difficult to get the two values to have a comprable exposure (i.e. photon mapping was consistently too dark). Recent changes to the way light is scattered have made this matter worse but are conceptually necessary to get the simulation to be correct. Needless to say, I had to fudge the light power manually until the image 'looked' okay. Very imprecise but good enough for today. Here's what the final command line looked like. Note that I bumped the number of photons up to 25M to help fight noise which can be particularly noticeable for indirect lighting:

lighter2 --directlight=raytracer --noglobalambient --forcerealistic --lightpowerscale=8.0 --indirectlight=photonmapper --numphotons=25000000 --maxdensitysamples=5000 --sampledistance=20.0 --nofinalgather --lmdensity=20.0 --pmlightscale=16.0 data/NewCornell

This image shows the results of lighter2 combining raytracing and photon mapping (for direct and indirect light respectively). Note the brighter shadows and ceiling as well as the indirect brightening happening on the rear box. All of this increases the realism of the final image at the expense of noise but also requires significant hand-holding and tweaking of variables to achieve.

The code I check in today will be able to do all of this. Note that I used an old version of walktest.exe to render these images (from the 08 SOC branch for lighter2). The one in my branch is still not working with light maps for unknown reasons.