Triplanar mapped bump problem - gamma issue? Tweet

[AWOLism]

Hello!

Whenever I have been using triplanar mapped bump maps I have always felt that there is something off, so I wanted to do a proper test.

I have set up two test scenes with two spheres and two planes, one of the planes and one of the spheres are using UV mapping, and the others are using triplanar mapping.
I used a UV test grid map to make sure the scale of the mapping is the same, and a simple image of some noise as bump.

When comparing the results, you can clearly see a huge difference in the bump map result. The UV mapped objects look as expected, but the triplanar mapped ones look very odd, rough and lacking highlights.
At first, I couldn't figure out why, but then I tried applying a Color Correction Node to the triplanar mapped image. With a gamma value of around 3.1, suddenly the result is looking more like the reference UV mapped noise.

Is this a bug, or intended result? The albedo map does not seem to be affected, as it looks the same regardless of mapping type.

Attaching renders and a ZIP with the test scenes.

[AWOLism]

*Bump* (pun intended)

[AWOLism]

It would be great if someone at Otoy, Bepe or Aoktar for instance, could have a look at this and offer some insight.

Thanks
Andreas

[jayroth2020]

Hi Andreas, the images cannot match, based upon the way you have it set up. The UV cube and sphere image maps are scaled at 1.0, but the Triplanar cube and sphere image maps are scaled at 0.05. That scaling is significant, and you will see some differences as a result. Your gamma correction attempts to resolve the differences, and that is a reasonable approach to take in this scenario.

[AWOLism]

Hi Andreas, the images cannot match, based upon the way you have it set up. The UV cube and sphere image maps are scaled at 1.0, but the Triplanar cube and sphere image maps are scaled at 0.05. That scaling is significant, and you will see some differences as a result. Your gamma correction attempts to resolve the differences, and that is a reasonable approach to take in this scenario.

Thanks for the reply, Jay. I appreciate it.

However, I don't feel much wiser.

Yes, you are correct that the triplanar texture is numerically significantly smaller scaled, but visually it's the same scale as the UV mapped material, as you can clearly tell from the colored checker map I used as scale reference.
Triplanar mapping set to a scale of 1 is huge, so to match the scale of the UV mapped object I have to scale down massively.

So my follow up question is, how should I be approaching this to avoid the rather unpredictable result from the neccessary downscaling and then needing to compensate with gamma correction?

Thanks
Andreas

[bepeg4d]

Hi Andreas,
Jay's answer is more than wiser!
The Scale is crucial in Octane, and by default, it is designed to render at 100cm.
If you have a small object, and you also reduce a lot the scale, you go out of range for Octane.
Look at what happens if you change the Scale to 10, and the UV Transform to 0.5:

ciao Beppe

[AWOLism]

Hi Andreas,
Jay's answer is more than wiser!
The Scale is crucial in Octane, and by default, it is designed to render at 100cm.
If you have a small object, and you also reduce a lot the scale, you go out of range for Octane.
Look at what happens if you change the Scale to 10, and the UV Transform to 0.5:

0008FA00-1E95-40C6-BBBB-8B5A0FB985B1.jpeg

ciao Beppe

Hi Beppe!

I understand. It probably makes perfect sense from a programmer/technical perspective. I understand that there must be some kind of scaling/interpolating/filtering going on in the engine for this type of thing, and that there might be limits or problems with massive scaling.
But from my user perspective I found it kind of confusing, as I had not encountered the same problem back when I was using for instance Vray. And it makes using Triplanar maps a little less appealing.

Is it possible to add it to some sort of wishlist for things that could be "improved"? If it can be improved?

Anyway, thanks for the reply!

[bepeg4d]

You are welcome

Please consider that OctaneRender is not like other render engines, the Scale is crucial, due to its unbiased physically based nature.
This is why we have the Ray Epsilon value in the Kernel, that defines the precision of the rays, in relation with the scale of the project.

Anyway, since this technical limitation is not related to a single plugin, but to the general core SDK, the best way to inform the core devs is to use the following form, and have some votes from other users:
https://render.otoy.com/requests/?qa=ask

Happy GPU rendering,
ciao Beppe

[AWOLism]

You are welcome

Please consider that OctaneRender is not like other render engines, the Scale is crucial, due to its unbiased physically based nature.
This is why we have the Ray Epsilon value in the Kernel, that defines the precision of the rays, in relation with the scale of the project.

Anyway, since this technical limitation is not related to a single plugin, but to the general core SDK, the best way to inform the core devs is to use the following form, and have some votes from other users:
https://render.otoy.com/requests/?qa=ask

Happy GPU rendering,
ciao Beppe

Cool, thanks! I will make a request there.

Cheers
Andreas

[sethRichardson]

You are welcome

Please consider that OctaneRender is not like other render engines, the Scale is crucial, due to its unbiased physically based nature.
This is why we have the Ray Epsilon value in the Kernel, that defines the precision of the rays, in relation with the scale of the project.

Anyway, since this technical limitation is not related to a single plugin, but to the general core SDK, the best way to inform the core devs is to use the following form, and have some votes from other users:
https://render.otoy.com/requests/?qa=ask

Happy GPU rendering,
ciao Beppe

Scale is crucial, so what happens when you are working to scale and Octane is still wrong lol. You are breaking your own rules. Say I have a product that is 50mm x 100mm x 25mm. I cant properly texture the plastic texture on it NO MATTER WHAT YOU DO. The only way I can do it is if I scale the scene by 10x so that the dimensions of the product are now 500mm x 1000mm x 250mm, of course this breaks things like oh I dont know DOF, sss, etc etc. Because you are no longer working to the correct scale but having to cheese. This means anything else you add to the scene will also need to be scaled up even though its not physically accurate anymore.

Perhaps you just dont understand the actual problem?