Disabling "Cast Shadows" for transparent objects disables their opacity maps

[marty030]

Could you please describe under what condition it is fine? The checkered plane has "CastShadows" Off AND the green material has reflectivity?

[Alex_M]

I didn't do any changes to your file. I just opened it and hit render. Are you sure you successfully installed Update 1? Maybe try installing again?

[Margarita.Stoeva]

Hello!

I was able to reproduce the issue (I changed the reflectivity of green plane as described) and it's now logged in our bug tracking system. Thank you for reporting it.

Best regards,
Margarita

[marty030]

Having updated to v1.1 the error is still apparent when using V-RayLights (not with VSun tho).

Any chance of a quickfix?

[matanov]

Having updated to v1.1 the error is still apparent when using V-RayLights (not with VSun tho).

Any chance of a quickfix?

Unfortunately we didn't had the time for this one, but when it's fixed, I can send you a build to test it. Are you ok with this?

[marty030]

Ok. And yes, I would appreciate it.

[marty030]

Hi,

so, here is a new V-Ray Update 1.2 and yet this specific bug is STILL NOT FIXED. I wonder how hard one would have to rant about it to get the attention. I am really annoyed.
This problem has been brought up by Alex_M in June 2018. That is 9 month ago. You could produce a new life in that time frame. Or another ridiculous upgrade of 3ds Max.
I dont know but maybe Chaosgroup´ focus is too scattered on too many things. I´ll shut it now (and wish big studios of the Arch/VFX industry with more leverage would step forward to speak up big time).

In the attached scene file you can try it for yourself, again. The problems occur with V-RayLights, but not with the V-RaySun.

[Margarita.Stoeva]

Hello!

I'm sorry that this issue is causing so much trouble with your workflow. I forwarded your feedback to our developers to help in pushing it up in the To do list.

Thank you for the scene, I can see you tried debugging what works and what - not. I can suggest two workarounds that may help in ceratin cases:
* If you have just a few lights in yours scene: Instead of disabling the Cast Shadows in the object properties of the opacity-mapped plane, set it back on and use the Exclude list in the VRayLight parameters to exclude the opacity-mapped plane from Shadow Casting. This is not perfect because it will have to be done in each light that contributes to the specular highlight of the area behind the plane.
* If the opacity-mapped plane (Plane002 in your scene) is not needed in any reflections or refractions in your final frame then just disable its Visible to Reflection/Refraction option together with the Cast Shadows in the Object properties.

The general workflow that should work without the need of any additional tweaks in object properties or exclude lists mentioned above would require deleting the opacity-mapped plane object from the scene and shading the other geometry with a VRayBlendMtl that is using the opacity-mapped material as its coat layer. You can use this VRayBlendMtl in a Multi/Sub-Object material or assign it directly to the geometry and use a VRayMultiSubTex to set the opacity-mapped texture to shade just the polygons that you need after assigning to them respective polygon material ID and adjusting the mapping of the textures accordingly.

I hope this will help you until we work out an actual fix here.

Best regards,
Margarita