Bump: Vray Vs Corona

[doomgrave]

After some observations I've found that in a lot of situations Corona bump reacts better to the light than Vray. This is expecially true for environment light.
This is a simple Studio plane setup, with only environment light and simple clay material with checker as a bump with blur:1,3 both for Vray and Corona.

In Vray there is a sort of glow in Vertical Lines that in corona are shadowed, in general it seems that corona ones are a bit more natural and deeper.

[FSGFX]

do the same with a displacemetn map... to see which one is correct...

[joconnell]

Try putting your bump map through the vray colour2bump map too.

[vlado]

The Checker map is not a suitable example for making any comparisons about bump mapping. Your comparisons will be more accurate if you use a bitmap texture.

From then on, the default bump implementation of V-Ray tries to follow that of the Scanline renderer and mental ray (regardless of any drawbacks it might have). We have an alternate implementation in the form of the VRayColor2Bump map, as joconnell pointed out, which you may like better. To make the comparisons more accurate, you should also compare with displacement as the ground truth.

Best regards,
Vlado

[doomgrave]

Tried displace, highlighted zones are correct in vray, and also in corona. Vertical lines should be invisible-dark not highlighted!
Tried also VrayColorToBump, do not work... The only thing that reduce a bit that weird lines is to use a "VrayNormal+VrayBumptoNOrmal" but are still present.

[vlado]

Here are my tests:

V-Ray displacement vs VRayColor2Bump:


Corona displacement vs Corona bump:


It is true that the V-Ray bump has some brighter edges, but if you flip the images, overall it is quite close to the same amount of displacement. Corona's bump is more subdued and more different from the displacement result; I could not get more pronounced bump from Corona no matter how much I pushed the bump amount.

In any case, like I said, a Checker map is not the best test for bump mapping. On the other hand, compare the below images with a Noise map for bump where Corona produces dark areas which are missing from the V-Ray render:


I couldn't really say that one is better than the other; they are just different. Insofar as bump mapping is a cheat, "better" is a very relative term.

Best regards,
Vlado

[dean_dmoo]

Looking at those images, and it's something I recognise when using bump for floor or wall tiling, the highlight in the vray bump is just too strong imo. It's looks brighter then any other part of the image, whereas the corona one looks equal than the background. The highlights for the displacement for both look to match the brighest part of the background, so look natural.

[vlado]

It's looks brighter then any other part of the image

If you measure the RGB values you fill find that it's about the same as the illumination on top of the sphere which is normal as that part of the bump is also facing up.

the highlight in the vray bump is just too strong imo

<shrug> imo it's about right.

Best regards,
Vlado