Canyon series 1

[Tangled-Universe]

A series of canyon's I've been working on...

Little fun fact; there's only one lambert shader as surface shader (w/o translucency and w/o masks).
The sand has the same colour, though ever slightly lighter with fake stones (which uses built-in RGB colour variation) as sand grains.

[Doug]

really good pics

i could put some petroglyphs all over those walls

[Dune]

Extremely cool, especially the last POV, with the great variation in hues and darks. Very subtle. Did you use (a.o) the water shader for sand displacement? I actually never thought of using a lambert shader for surfaces like this. I guess the translucency and the PT light reflections give it such a subtle 'gloom'.

[Tangled-Universe]

Thanks guys!

Ulco, for the water I just used 2 fractals mixed, one perlin mix 2 and the other ridges, both with low octaves.
The lambert shader does not use translucency. Good that you mention, I adjusted my post to this.
Basically it's just the node I used, it could have been a surface layer with the same colour as well. Would have done the same.
It's not rendered with PT, actually. All the colour and hues are from the GI. I used very high cache detail, like 16 with sample quality 32 (hence filename).

[Dune]

Thanks Martin. Interesting fact about the cache detail. I wonder how it would look in PT.

[Tangled-Universe]

Thanks Martin. Interesting fact about the cache detail. I wonder how it would look in PT.

Welcome!
Yeah me too, but somehow it's crazy slow with PT. I might try Thursday overnight since I won't need my PC until Friday noon.
Which one should I choose you think? I probably can't render it bigger than 1280 wide/tall.

[Dune]

If you ask; the latter, vertical one appeals most to me, because of the contrasts. PT has 'trouble' with tiny displacements+reflection, that may be the 'problem'. But even a very small PT render will show the differences, I'd say.

[Tangled-Universe]

I agree with you about the vertical one being the most interesting, for the same reasons.
The scene does not contain any kind of reflective shader. It's really only one single lambert shader with bright orange colour which does all the work in conjunction with GI.

I'm afraid I have to postpone my plan to do a PT render of it.
I just trimmed down the entire setup to basically only 2 simple shape shaders which create the canyon and somehow that takes 45 minutes vs 37 seconds for non-PT.
This means that my 5'ish hour render for that vertical one will take 20 days. No thanks haha...
There must be a reason for why TG doesn't like this particular and I guess rare situations, since normally it's only a couple of times slower, not 2 orders of magnitude.

[Dune]

I can imagine   Strange that it takes so long, it doesn't look overly complicated, and displaced. Too many shaders before a compute perhaps? Perhaps it would be possible to make the scene with 2 cubes as walls. You'd only miss the subtle transition with the floor then, but it might be faster (no compute needed, I'd say).

[Tangled-Universe]

No as I said I deleted all the nodes except the 2 simple shapes which create the walls +1 compute and lambert and only those 4 nodes take 45 minutes to render vs 37 sec non-PT.

[Dune]

Didn't read it well. I see now.

[blattacker]

Doing some quick experimentation on my end, the lambert shader does seem to take longer to render with the path tracer, but color seems to have a more pronounced effect. For reference, the experiment I did was just two simple shape shaders with no other displacement, and I tested rendering with the default "Base colours" pf shader, the default pf edited to introduce color rather than just greyscale values, a lambert shader with a grey value, and a lambert shader with a color value. All other setting remained the same. My results were:

• Render Settings: 800 x 450; 0.5 Micropoly detail; 3 Anti-aliasing (all default settings); Path Tracer; Max paths per sample 144 (high value to approximate a "worst case scenario")
• Greyscale PF shader: 54 seconds
• Color PF shader: 2 minutes 43 seconds
• Greyscale lambert shader: 2 minutes 30 seconds
• Color lambert shader: 8 minutes 1 second

Perhaps a workaround to try it out with the path tracer would be to render it out in greyscale and then either add color in post or process it like a black and white photograph?

[Dune]

Interesting. Might well be the Lambert indeed. I wonder what's so 'special' about it, makes it different from say a one color surface shader, it looks so basic. Perhaps the (expensive) way of calculating light?

[blattacker]

Perhaps the (expensive) way of calculating light?

I think that might be the case. If my (extremely basic) understanding of rendering principles is correct, I believe Lambert shading is a form of reflective shading, albeit diffused reflections. I would guess that those diffuse reflections require additional calculation. Moving into pure speculation, color would likely increase calculation time as it would reduce the amount of bulk operations that could be performed, since each ray could have different color values based on what color(s) it picked up (or, as it works in the real world, I guess it would be which colors/wavelengths got absorbed rather than reflected) along the way, but again, that's just pure conjecture on my part. I'm not quite clear on the scope of the physical aspect of physically based rendering.

[Tangled-Universe]

Doing some quick experimentation on my end, the lambert shader does seem to take longer to render with the path tracer, but color seems to have a more pronounced effect. For reference, the experiment I did was just two simple shape shaders with no other displacement, and I tested rendering with the default "Base colours" pf shader, the default pf edited to introduce color rather than just greyscale values, a lambert shader with a grey value, and a lambert shader with a color value. All other setting remained the same. My results were:

• Render Settings: 800 x 450; 0.5 Micropoly detail; 3 Anti-aliasing (all default settings); Path Tracer; Max paths per sample 144 (high value to approximate a "worst case scenario")
• Greyscale PF shader: 54 seconds
• Color PF shader: 2 minutes 43 seconds
• Greyscale lambert shader: 2 minutes 30 seconds
• Color lambert shader: 8 minutes 1 second

Perhaps a workaround to try it out with the path tracer would be to render it out in greyscale and then either add color in post or process it like a black and white photograph?

Thanks for taking the time and effort to look into this. I already did similar tests last week and reported my findings to the team. Something might be going on, but may be also not. Let's see.
My conclusions are similar, somehow bright saturated colours take a big hit in this situation.
It's fine the PT is slower, but usually not 100x. Rather 1.5-10x slower.

Your findings are similar to mine, but some info is lacking.
For example, lambert and surface shader render at equal speed for me.
PF is faster, but that's because the low colour is black. Setting both to the same colour as lambert results in only slightly slower render, which makes sense since to me.

Your suggestion at the end can't work, because with grey colour you basically omit GI. All the various shades and saturations of colours you see in the renders come from GI.
 

Perhaps the (expensive) way of calculating light?

I think that might be the case. If my (extremely basic) understanding of rendering principles is correct, I believe Lambert shading is a form of reflective shading, albeit diffused reflections. I would guess that those diffuse reflections require additional calculation. Moving into pure speculation, color would likely increase calculation time as it would reduce the amount of bulk operations that could be performed, since each ray could have different color values based on what color(s) it picked up (or, as it works in the real world, I guess it would be which colors/wavelengths got absorbed rather than reflected) along the way, but again, that's just pure conjecture on my part. I'm not quite clear on the scope of the physical aspect of physically based rendering.

Lambert shader is a diffuse shader. Nothing special going on with that compared to the colour from a PF or a surface layer. Those are lambertian models too.
My lambert also does not use translucency and the (test)scenes also don't have reflectivity. It's only 1 simple diffuse lambert shader.
As I said normally PT renders 1.5-10x slower, depending on a lot of scene-related factors, but this performance hit is unusual in my experience.