Edge Boundary Checking Shadow Error

[RC2292]

Hi,

Whilst rendering grass and using Edge boundary Checking, the grass itself is being trimmed correctly to the edge of the spline but there remains contact shadows where the grass would have been had edge mode node been selected.


See image with render regions as follows:

Top is Point Checking

Mid is no FP

Bottom is Edge Boundary Checking with the unwanted contact shadows.

Closest mention I've seen on the forum is here: https://forum.itoosoft.com/forest-pro-(*)/boundary-checking-problem-leaves-either-shadow-or-brighter-patch/msg18748/?topicseen#msg18748

Have tried upping the VRay transparency limit and decreasing the density but doesn't have any impact.

3ds Max 2022
VRay 5

Thanks

[Paul Roberts]

Hi,

Sorry to hear you're facing that issue. In the past, that's always been resolvable by upping the transparency levels. Could you upload a simplified sample scene that reproduces the issue so we can take a closer look?

Thanks,
Paul

[RC2292]

Thanks for looking at this Paul.

Attached a simplified scene. Somehow the effect is more subtle but hopefully still noticeable.

[RealViz]

Don't have Vray-dirt enabled on the pavement? You need to turn on "ignore invisible" or the old-fashioned "work with transparency"

[RC2292]

Good shout but no, not using Vray-dirt.

[RealViz]

I've gone over the scene and the problem is the grass material. Unfortunately I don't have all the assets (textures) and so can't identify it. However, if you assign the same material "Grass" you have in the mtl editor to all FP objects it renders without problems.

[RealViz]

I see a problem. Two objects have multimaterial "_fp_grass" and it contains Standard/Legacy materials. That's the problem.
So it's not iToo's fault ;-)

[RC2292]

Thanks again.

Don't think it's related to to materials. Apologies in my haste I didn't strip the max file entirely of maps. I've reattached the clean version to the post above.

To show its not linked to materials I've rendered the scene with a grey Vray override material both with and without the grass. You can see the region without the grass doesn't produce the artefacts where as the one with grass does.

Are you getting these with a Vray override applied too?

[Paul Roberts]

Hi,

This would appear to be related to the irradiance map settings. If I change the Primary Engine to Brute Force the issue disappears. If you need to stick with irradiance maps, You may find increasing the quality will help to fix the problem.

Best,
Paul

[RC2292]

Thanks Paul, I'll give that a go.

[RC2292]

Yes just tried that and you're right, it's irradiance related.
As I increase the quality the they become smaller.


Thanks!

[RealViz]

Hi,

This would appear to be related to the irradiance map settings. If I change the Primary Engine to Brute Force the issue disappears. If you need to stick with irradiance maps, You may find increasing the quality will help to fix the problem.

Best,
Paul

Yes this is generally a problem with IR when using non-standard materials. If the correct V-ray material is used everything is OK even when using IR. But I agree that BF is a much better method today.

[RealViz]

I can see the problem now. There are some old settings carried over from an older V-ray. If you reset the V-ray settings (just change the render to another one and back). Then everything renders correctly even with IR.