New PBR Engine!

A new renderer and new shaders!

Clarisse 3.0 brings a new Physical (physically based) shading model which consists of a new Path Tracer renderer and new set of materials, volumes and lights.  This new physically based engine provides state of the art shaders and advanced sampling techniques. All these have been possible thanks to the years of collaboration with Double Negative R&D rendering team and specially with the help of Emmanuel Turquin! You’ll see, it is now way simpler (maybe even too simple ;)) to create photo-realistic images with these new shaders in Clarisse.

The quick and dirty test

buddha2_occlusion
GGX Reflection with occlusion node driving roughness and its reflectance

Old vs New shading model

While the new PBR engine a rendering cost, (it is slower for the same amount of samples) you do get a better sampling. This means that you should need less samples to get rid of the noise. The other good thing is that now Clarisse is finally able to render caustics (both from specular and transmission) as you can see in the previous image.

Please don’t get your hopes up too high: the new path tracer is still a unidirectional one. This means that, while Clarisse resolves refractive caustics, they require a large number of samples to get noise free.

Getting started with PBR

When you start Clarisse, Clarisse will prompt you with the default shading model you wish to use. Make sure to select: Physical. That way, the default scene will be created with the path tracer and a Physical Distant light.

What are the big changes?

There are two dramatic changes to what you were used to in the legacy shading model.

First, attributes controlling the sampling are now in sample per pixel (spp). This means that you set the actual number of sample you wish to use. In the legacy model, the actual number of samples fired were the square of the input value. For example, 8 meant 8×8 (64) samples, now, 8 spp means that 8 samples are actually fired.

This is true for any attribute controlling samples including antialiasing.

Secondly, the new shading model doesn’t provide anymore a GI light. GI is automatically on by default. The quality of the GI and all secondary rays (including reflection and transmission) is set by the attribute Material Sample Count you’ll find in the path tracer. Clarisse will perform MIS and automatically distributes the number of samples (see this as a sampling budget) to the different BxDF according to the material. While that works pretty well, sometimes, you may want to add more sample to the glossy reflection for example. In that case, oversampling specific channels to launch more rays for glossy reflections for example is still possible using the per ray type multipliers.

Moreover, while sampling is now controlled directly at the path tracer level, you can still override any of these values at the material level for finer controls!

A quick word about lights

There are now two kinds of lights: infinite and area lights. Infinite lights are lights that aren’t relying on a physical geometry such as environment and distant lights. On the contrary, area lights rely on a internal geometry such as (finite) plane, sphere, spot etc… You will also note that area light now properly takes into account arbitrary scaling. The good news is that this doesn’t affect overall sampling quality.

PBR feature minitour video

Finally, please forgive us but we didn’t have the time to complete the new PBR documentation for 3.0 RC1 release. Fortunately, Yann prepared a small video to guide you through and explain you the basics of this new PBR engine.

Enjoy! 😉

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