![]() ![]() We also look at the pros & cons of "internal RMS rendering" vs "external RPS rendering" while debugging our absorptionGain settings. We go through each parameter of this material shader and focus on IOR, absorptionGain, and absorptionColor inside our new scene, noting the raytraced refraction and caustics with our PathTracer Integrator. We start with a brand new scene: an interior "kitchen" with glass statue, to focus on the PxrGlass BxDF for this lesson. Finally, we touch on the difference between an geometry sphere with "emissive" shader parameter, and a spherical area light. An even better example is putting a light source enclosed in a "frosted glass" housing, showing the VCM will find the light path but the uni-directional path tracer will not. We take a look at this scenario through some diagrams explaining the light paths, and the "vertex connection" part of the VCM. One great example for this kind of scenario is a "recessed lighting" example, where there is no direct visible path to the light source, it needs to bounce off multiple objects to connect with objects in the scene visible to the camera rays. We want to explore scenarios where the uni-directional Path Tracer simply doesn't find the path to the light, and where we need to use the bi-directional VCM. ![]() Summarizing we see how the VCM works better on interior scenes with multiple dimly lit light sources, lots of bounce, and sharp caustics. To really see the features of the bi-directional VCM we explore a new interior scene setup with sharp caustics on glass and metals, and show how Merge Radius Scale affects the quality of our caustics and render time. We touch on comparisons of Pixel Variance to traditional RenderMan's PixelSamples setting when shading depth-of-field. We look at some important quality settings with both the Path Tracer and bi-directional VCM: Pixel Variance and Merge Radius Scale. We then take our Path vs VCM into a "Cornell Box" scene, and see the nice subtle bounce we get from the VCM with an arealight, as well as nice handling of caustics and refractions through glass. Then we jump into exploring Path Tracing (uni-dir) vs VCM (bi-directional) in our scene with a high-contrast dome light, and find that using a lower contrast dome light source really makes a difference in reducing artifacts in our VCM. Doing this we notice we're not getting indirect contribution from our emissive geo in the reflection sphere, so we cover how to set that with an attribute, both global and on a per-object basis, and how it looks like in our RenderMan RIB. We start off by continuing with our "emissive" geo/light source from the previous lesson, and animate the sphere geo to see its effect on the ground and our car model. We also render our "SmartCar" asset with the same material, adding metallic and anisotropic features of the PxrDisneyBRDF. This leads to focusing on the "Emissive" property of the PxrDisneyBRDF material, inspecting and experimenting with different sampling settings for ideal renders. We then jump into a RenderMan Studio session with a new asset, the Stirling model provided by Pixar's RenderMan team, and start off by rendering in the REYES mode - we do this deliberately to segue into rendering in RIS with the same scene, and show how we have to re-assign all the new RIS/BRDF materials. ![]() We look at diagrams and corresponding renders of how these different raytrace modes traverse and sample our scene with camera, light, and shadow rays. We start off with illustrating the concept of bi-directional path-tracing, in the context of distributed ray-tracing and uni-directional path tracing. New Disney "principled" BRDF via "PxrDisney" shader: the paper it was based off, explanations, and render examples. Answering questions to "What is RIS & Path Tracing?". Outline of new features, definitions, and some of the things we'll be doing with them. ![]()
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