TU Wien Rendering #34 - SDS Transport, Photon Mapping

We have learned quite a few powerful algorithms for global illumination, but there still seems to be a peculiar scene with a torus inside a block of glass that just doesn't want to give in and render. It contains specular-diffuse-specular interactions that are particularly difficult, or often impossible to sample with traditional random sampling. We also talk about the first biased algorithm, Henrik Wann Jensen's masterpiece called photon mapping. This algorithm relies on the years of knowledge - for instance, we know that indirect illumination is usually a low-frequency signal that lends itself to the idea of using interpolation for missing samples instead of complete exhaustive sampling. This introduces bias, so the algorithm cuts corners - see for yourself if it's worth it!
About the course:
This course aims to give an overview of basic and state-of-the-art methods of rendering. Offline methods such as ray and path tracing, photon mapping and many other algorithms are introduced and various refinement are explained.
The basics of the involved physics, such as geometric optics, surface and media interaction with light and camera models are outlined.
The apparatus of Monte Carlo methods is introduced which is heavily used in several algorithms and its refinement in the form of stratified sampling and the Metropolis-Hastings method is explained.
At the end of the course students should be familiar with common techniques in rendering and find their way around the current state-of-the-art of the field. Furthermore the exercises should deepen the attendees' understanding of the basic principles of light transport and enable them to write a simple rendering program themselves.
These videos are the recordings of the lectures of 2015 at the Teschnische Universität Wien by Károly Zsolnai and Thomas Auzinger
Course website and slides → www.cg.tuwien.a...
Subscribe → www.youtube.com...
Web → cg.tuwien.ac.a...
Twitter → / karoly_zsolnai

[@sewardhacker3080]

I don't know how good this technique would get, but what if you position the camera in 1:29 at the poit where the light is located, and try to render the scene from the light source point of view? Doing so, try to take account of what portions of the diffuse plane you see from behind the glass cube (the light source would "see" the same way). In other words, we would try to highlight all the points in the diffuse surface the camera rays were able to reach, these would be the same points the rays emitted from the light would reach. Then we try to bake this "photon map" and simply add it to the diffuse plane texture in the end. Of course there are a lot of problems whit this method (it wouldn't be that good with extensive light sources, to begin with), but perharps it would give a more realistic-looking caustic pattern in some situations, whitout lots of calculation?

[@SarahC2]

An easier set up is simply a frameless glass window perpendicular to a diffuse ground and placed a meter up with a light source above and to the side. Light going through the glass to the ground, and then back through the glass looks SUPER DARK. (SDS path) Just using two objects and a light source! It's horrific that this "simple" physical setup shows non-photorealistic results in most renderers!

[@juancarlosgzrz]

Are you indian?

[@depthsofdejenol8026]

he's hungarian

[@juancarlosgzrz]

@@depthsofdejenol8026 nope, hear his accent, indian

[@diharawijetunga4173]

@@juancarlosgzrz ah of course! I forgot that Károly Zsolnai is an indian name.

[@juancarlosgzrz]

@@diharawijetunga4173 thank you that's what I've been saying

[@top.of.reddit]

@@juancarlosgzrz He was sarcastic.