displacement 'decal'

[Gijs]

How can I apply a displacement decal properly? If I want to affect only certain faces it still applies the decal to the whole object. I can't find it in the manual. I have searched the newsgroup for some articles, but still can't figure it out.

Gijs

[Biohazard]

You should use a mask in you diplacement map slot.
A bitmap would do the job, but if your displaced object is too big, I recommand you to use a vertex color instead. That's cheap and very efficient.

[J_Bug]

I like the vertex color idea didn't think of that but good to know it's a better solution.

Thanks,
--Jon

[Gijs]

Thanks for the reply, I will check. Never worked with vertex color, so it will take some time to figure this out I suppose.

Gijs

[Gijs]

Finally found some time to try this out. It works really good. Thanks again for the solution.

[travistlo]

if you guys wouldnt mind, Can someone explain that technique? (Displacement with vertex color)

Thanks,
Travis

[Biohazard]

Yep,

In order to spare memory and avoid huge bitmaps for masking areas on your mesh when displacing :

- Simply add a "mask" on top of your displacement map (bitmap or wathever).
- Then add a "vertex color" in the mask slot (to control diplacement or not).
- At last, add a "vertex color" modifier on your object, under the vray displacement mod. The important thing is that you can collapse that modifier after painting. The vertex color infos will stay.

Then paint your object : White for displacement and black for none.
The results will depend on the tesselation of your mesh, but I guess you'll start from a moderate tesselated object. Else, refine a bit your mesh around the areas where you want to avoid displace.

That's simple like that. I love elegant solutions.

[Gijs]

Maybe a bit double information, but this is how I did it:

in the object modifier stack add a vertex paint, a UVW Mapping and a VrayDisplacement modifier.

set object to 3d mapping and check in VrayDisplacementMod under 3D mapping params: use object material

now in the Vray material, mappings, put a mask map in displacement slot. Leave the value to 100, rather control the displacement in VrayDisplacementMod.

The Mask map now consists of two things: the map and the mask. The map is your displacement map texture. Put a vertex color map in the mask slot.

The nice thing now is that you can make the displacement map easy visible in the viewport.