VRayDirt - Z Bias error

[mattclayton]

Hi All, any help with this would be appreciated!

When increasing the Z bias on the VRayDirt, i'm getting some odd results. I've attached some example images and accompanying settings. Basically when increasing the bias above 1 the underside of geometry changes either to the diffuse colour or to 100% black;

Sample 01: Normal setup, no bias


Sample 02: Z Bias = 1...notice the diffuse colour has appeared.


Sample 03: Z Bias = 2 (or higher)...underside now 100% black.


(Colours here are just to show clearly what's going on.)

So any thoughts/advice!?

Cheers guys (gals)

Matt

[Svetlozar Draganov]

First we would like to welcome you to our community

VrayDirt cannot calculate properly the color of surfaces which normal coincides with bias-axis.
In your example the surfaces facing down(+Z/-Z) have wrong color since the bias offsets the DirtMap in Z-direction while the map only exists in XY-plane.

You can fix that by using lower value for bias and greater value for distribution. Find a bias value that doesn't produce a bizarre color of the surfaces facing bias-axis and then increase the distribution value until you get the effect you are looking after.

It would be great if you could post another example with the accompanying settings afterwards - it would be helpful for people facing the same issue.

Let us know if you need any further assistance on that matter.

[mattclayton]

Thanks for the welcome.

And thanks for the advice, seems to have done the trick. Results below;



I did have to increase the radius slightly and drop the falloff to get a similar gradient but looks about right.

As a bonus the faceting that was occurring around the curved edges has smoothed out as well, which is nice!

Cheers
Matt.

[Svetlozar Draganov]

This one looks much better
Thanks for the sharing.