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Clarisse GI bounces

Unread postPosted: Sun Dec 15, 2019 12:00 pm
by oddvisionary
Hi, before reading further, note that this is not a forum post to bash on Clarisse, and the tests bellow are quick tests done on some free time.

As I'm using other renderers outside Clarisse (particularly in Houdini these days) I noticed how darker the GI bounces (diffuse ray depth) is in Clarisse. So I run several tests with some assets in RenderMan and 3Delight for Houdini (Cycles too but inside Blender).

I've always felt the lack of natural "GI bleeding" resulting in very dark (too dark) shadows in occluded area. Beside speed improvement that we get on most new releases, I wanted to point that out. Such little change in the Path Tracer could really have a big impact on a scene.

Re: Clarisse GI bounces (weak?)

Unread postPosted: Sun Dec 15, 2019 2:03 pm
by ayanik
After having used and tested several render engines I have the same opinion. Somehow the bounces don't feel like they are contributing as much as in other engines. Even when disabling russian roulette, raising the total depth to 40 and disabling clamping. Lighting feels artificial because of this.

After a few bounces the diffuse depth seems to make almost 0 difference.

Re: Clarisse GI bounces (weak?)

Unread postPosted: Sun Dec 15, 2019 3:53 pm
by Kramon
Yap can confirm i was telling this long time ago, GI is very very weak have to boost it in compositor sadly but still looks not that good. At first i was thinking that it is just russian roulette etc... but after more test, it is just what it is makes rendering look very very flat... and compute expensive.

Re: Clarisse GI bounces (weak?)

Unread postPosted: Sun Dec 15, 2019 8:24 pm
by sam
Jin: Send the scene..

Re: Clarisse GI bounces

Unread postPosted: Mon Dec 16, 2019 9:48 am
by oddvisionary
Reposting here what I wrote on Discord:

After testing several scenes and assets where we can see the GI bouncing off of object and surfaces (car interior, room interior etc), most results compared to 3Delight (or RenderMan) are matching Clarisse results. I tested on both with matching shaders and lighting (distant light, area light and HDRI).
HDRI_10_RayDepth.jpg
10 Ray depth with an HDRI (pre converted to ACEScg).


But there is still one scene where Clarisse does not match 3Delight (or RenderMan). I don't know if the scale has a secondary effect on the GI diffuse ray depth (bounces) but there is an obvious difference with this small teapot scene.
2019-12-16_09-25-34.jpg
Both scene with matched ray depth value, hdri. Only the camera is not 1:1 matched but eye balled (lack of time to fix an issue related to it).


Attached bellow are fairly matched GI results + the teapot scene result. Ray depth + lighting is always matched, with a 50%grey diffuse shader (no reflection or anything else).

Re: Clarisse GI bounces (weak?)

Unread postPosted: Thu Mar 05, 2020 6:40 am
by RayCaster
ayanik wrote:After having used and tested several render engines I have the same opinion. Somehow the bounces don't feel like they are contributing as much as in other engines. Even when disabling russian roulette, raising the total depth to 40 and disabling clamping. Lighting feels artificial because of this.

After a few bounces the diffuse depth seems to make almost 0 difference.


Is there much need for more than 3 diffuse bounces? (or 3 GI bounces which i think might be similar?)

Re: Clarisse GI bounces

Unread postPosted: Thu Mar 12, 2020 10:38 pm
by ambassador1
In some instances, yes, it can change the look/realism. In other engines its cheap enough to use more than one by default, which is not the case in Clarisse. In very dense/high frequency geo scenes, say a forest, you may not see much of a difference, but in interior type shots, you would.

Re: Clarisse GI bounces

Unread postPosted: Fri Mar 13, 2020 8:48 am
by mdkai
I agree, it's mostly depending on how long a ray would have a drastic change vs the previous bounce ..if red hits blue, reaches unlit areas or if it's keep inside a medium like clouds the effect is more pronounced

But most of the time rays will average in a regular environment without much more contribution and will have less effect with more bounces.