V-ray decal materials disappearing after (rhino)purge

[rene_rapati]

Yet another annoying problem:

When I use the Rhino purge command, my V-ray decal materials are purged when the decals are hidden.
Usually I only notice the problem after quite some time, so there is no easy way to fix the missing materials.

Steps to reproduce:

1. Open new rhino model;
2. Draw a solid cube;
3. Draw a V-ray decal on the cube;
4. Generate 2 new V-ray generic materials: make one red and the other one blue;
5. Apply the blue material to the cube and the red material to the decal.
6. Then it looks something like the picture below;
7. Hiding the cube and then (rhino) purge has no effect (as expected)
8. Showing the cube and hiding the decal then (rhino) purge, The red (decal) material is purged from the drawing. (NOT as expected)
9. If you are lucky enough to notice something wrong in the drawing, you can hit undo. Then the (red) material will be back in the drawing, but not assigned to the decal anymore!
10. If you are unlucky (like me) and only notice something wrong after quite some time working on the model......

Note that using the V-ray purge command does not have the same effect.


Before purge:

After purge:

Purge settings:


I'm using Rhino 8 (8.8.24170.13001, 2024-06-1 and V-ray 6.20.4.

[glennco]

rene_rapati
A work around I use:
Create Rhino layer "extra stuff" or "Vray decal bitmaps"
Make a flat surface, create Vray material & apply to that surface.
In Vray Decal, select that material.
Layer visibility can be turned off so it doesn't interfere with rendering or modeling.
Glenn

[rene_rapati]

glennco,
Thanks for the advice! I will try to use this method, but I have a lot of decals in my models, so this will take me a lot of extra time...

---

I have just tested the above steps with other V-ray geometries. As far as I can see, only an infinite plane can have a material assigned to it, but for this geometry the material is not purged when it is hidden...
So it seems the problem is restricted to V-ray decals...

[natalia.gruzdova]

Hello rene_rapati,
Thank you for your report.

I have linked this forum post to the internal Improvement case number VRW-4496 (Prevent Rhino Purge from deleting hidden materials).

Note that not only Decal material can be currently purged with Rhino Purge command but other materials from hidden objects as well, such as Clipper, V-Ray Fur, Proxy Mesh etc.

Which is why we generally advise to avoid using the Rhino Purge Materials option (please see this article) and use V-Ray Purge unused instead.

As glennco suggested you need to ensure that materials are not hidden - unhide (-Show command) everything before the purge (including hidden layers) if you decide to use Rhino materials Purge.