Bounce light/Ambient light
This is kind of bugging me . So if you have a scene with a sunlight with strong shadows, you get quite harsh dark shadow. If I add a HDR as an ambient source, then I get lighter shadows and the scene look quite nice
So why do i need to have bounce lighting on top of that
In Blender for example if I turn off bounce lighting completely and keep the HDR, the difference is minimal
the only reason i have it on it seems is so that I can control the reflection and transparency/transmission samples
i guess the difference in more noticeable in a scene with a simple cube and plane, bit in a complex outdooor scene, the amount of bounces seems not to matter as much, the ambient source seems to cotrol the scene more
I am not a rendering expert, but would welcome any advice
I have some nice results, but am just interested in it from a technical standpoint
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so yeah it seems that Diffuse indirect is not making that much difference to my scenes if if I turn it up to 1024
the scene seems easier to control with Fast GI Approximation fi i am Honest, but the docs say that this is for less high quality renders
Seems a bit easier in Vray , I think they have a GI multipler box or similar
This is my scene using fast GI approximation
scene with NO ambient lght 1 sunlught and imax bounces bumped up to max ( 1024)
if I clamp the direct light and increase the Sunlight to 50 strength for example I do get some bounce from the grass etc, but it looks kind of weird as it blows out the direct light
This is 1 sunlight+HDR with no bounce samples at all, so its direct light only. The only difference is on the glossy where it doesn't reflect the grass and trees
I guess the difference is that i am rendering an outdoor scene, not a room with light coming through the windows?
This uses Fast Gi approimation and brings the shadow brightness up quite well with minimum bounces
You are rendering with Cycles?
We include ray bounces because that's the way light works ('all models are wrong' notwithstanding) in the real world, and replicating reality is usually the ultimate goal of a path tracer. Obviously there are plenty of scenarios where the visual difference is minimal and you can take shortcuts like this.
Bounces contribute effects like radiosity and emission (and perhaps also shadow softening - unsure). Your test scenes don't have a ton of specular and have distant directional light so there isn't much opportunity for this in the first place. Glossier materials and more enclosed geometry with more lights may start to highlight the difference - you'd expect a desk lamp in a room to still cast some light on the ceiling despite not being pointed at the ceiling.
In some sense HDRI's are like precalculated atmospheric bounce light, so they're sort of doing most of the bounce light work for you in these outdoor scenes.
You do get quickly diminishing returns after just a couple bounce traces, as you've already discovered.
yes I use cycles mainly, eevee has gotten very slow of late
yeah I finally figured that out after 3 years messing around. i think its safe to say if it looks pretty good in my eyes , then I will stick with the
technique that gives me what i want, even if its not exactly the ' technical' the way to do it
It's the final image that counts after all .
i still pay attention to the glossy and transmission bounces, because that where i get most of the noise, but the diffuse in my scene is set to about 4 bounces, but I use 'Fast GI approximation' set to 1 bounce. This then acts like GI. If I set it to 2 bounces its acts like AO. I think it may
still be a bit buggy
I set my samples to 1024, and noise threshhold to 0.004 or similar to get a nice cleanish render
my scene is VR with 4096x2048 output, so each frame takes 15 mins approx
I use the denoiser in the compositor , because OPTIX is terrible