vray dirt odd gaps.

[super gnu]

im using vray dirt to add some dusty corners to glass. ive got it in the reflection and refraction level slots.. works well.. buuut... i get strange gaps in the effect.


ive tried changing the subdivs, AA min rate, noise threshold, subdividing the geometry finely... nothing seems to affect it.






any suggestions?

[vlado]

Could you post that part of the scene? Or email it to vray@chaosgroup.com

Best regards,
Vlado

[super gnu]

yes sure.. im trying to solve the issue here at the moment.. seems to work fine in the diffuse or reflection slots, but if i put it in the refraction level slot it goes a bit nuts.

- and ive just discovered it seems i can fix it by turning on "consider for GI" in the dirtmap settings.

no idea why this should be necessary, and for some reason it seems to make the dirtmap more grainy, but.. its not got any gaps any more.

do you still want a test file?

[vlado]

Yes, a test file would be good.

Best regards,
Vlado

[super gnu]

ok ive mailed it over.. however i think i finally got to the bottom of it.. issue is, without "consider for gi" turned on in the dirtmap, the gi is being calculated on, essentially, perfectly refractive glass... meaning totally transparent, and it doesnt bother doing any gi on totally transparent surfaces.

so, when the dirtmap makes the edges opaque in the final render, you get nasty gi errors.

this is proved by making the refraction colour / unoccluded colour something other than pure white.. even value 254 fixes the issue.. although it still looks a bit lumpy.. vray probably thinks it doesnt need to put much gi quality there.

anyway ive sent the scene, maybe you can add a tweak to avoid this issue..

cheers, Robin.