TwoSided materials and Displacement

[jiminy-billy-bob]

I have a Generic material with displacement settings.
This Generic material is wrapped in a TwoSided material.

When I apply the Generic material to a group, the displacement is visible in the render.
But when I apply the TwoSided, the displacement from the wrapped material is not used.

Is it expected? Is this a bug?
If it's expected, is there a workaround?

[konstantin_chaos]

Hi jiminy-billy-bob,

What you've described is indeed expected.
The Displacement in V-Ray Core is actually applied to the scene objects and not to the material.
And since in the Asset Editor the Displacement is part of the material, we basically have to re-connect it during rendering.
This is not always possible and you're just seeing one of the side-effects.

To ensure that the displacement is rendered you should apply the material with the displacement directly to the group.
After that you can apply any material that you like to the faces - the displacement effect will still be controlled by the group assignment.

Keep in mind that we are planning to change the displacement workflow in the future.
We will possibly introduce a new geometry type for it.
The material effect will be removed and you'll have to think about displacement more as a geometry property rather than a material one.
What do you think about that?
Does it make sense or you prefer the current workflow?

Regards,
Konstantin

[konstantin_chaos]

There are two more things to consider here:

1. Adding Translucency to any material
In V-Ray Next for SketchUp, update 2 you have the option to add Translucency attribute to any Generic material.
This removes the need of using 2 Sided materials in most cases.
It'll also work with displacement out of the box.

2. Keeping only Displacement attributes
Another option in update 2 is to remove all the layers and attributes from a material - keeping only the Displacement in.
You can then reference any material in it using this in-between material for the displace assignment.

I'd go with option 1.

[jiminy-billy-bob]

What you've described is indeed expected.
The Displacement in V-Ray Core is actually applied to the scene objects and not to the material.
And since in the Asset Editor the Displacement is part of the material, we basically have to re-connect it during rendering.
This is not always possible and you're just seeing one of the side-effects.

I see, thanks.

Keep in mind that we are planning to change the displacement workflow in the future.
We will possibly introduce a new geometry type for it.
The material effect will be removed and you'll have to think about displacement more as a geometry property rather than a material one.
What do you think about that?
Does it make sense or you prefer the current workflow?

I'm not sure.
One the one hand, it makes sense from your POV because of the core implementation, and from the users's POV for the fact that only one displacement can be applied to a single object.
On the other hand, I think most people think about displacement as a material property. Sure it deforms the geometry, but it is based on a texture/map, it follows the same UVs, etc. It's basically Bump on steroids. But nobody would think of Bump outside of the material.

1. Adding Translucency to any material
2. Keeping only Displacement attributes

I'm aware of that, and it's really great!
But we want to retain compatibility with previous versions of V-Ray.

[Mousa_SA]

The material effect will be removed and you'll have to think about displacement more as a geometry property rather than a material one.

I was not sure that would be an enhancement the first time you have told us about these changes, but after the forethought, I suppose that would be the right approach, here are why:

1-The using of displacement as "Material" usually increase the rendering time without knowing the reason and it is difficult to track which is the material that has a high setting for displacement, especially with large scale projects, so if we have it as "Displacement geometry property", it will be very easy tracked in the geometry tab like fur.
2-Displacement geometry property could be added for multible objects by copy the "Displacement geometry property" group inside other groups and components (Like Fur and Mesh Lights).
3-Since bump give good result for the far objects and is renderd fast, displacement Could be useful for close up objects only, so we will get the possiblity to add the displacement only for close objects, and the visibility for Displacement could be controlled for each scene by hiding the "Displacement geometry property" group.

4- Bump map could be copied as instance to the Map Slot in the "Displacement geometry property", which would give a consistent result for the size of the UVs.
5-Currently, It is not intuitive to understand why the displacement is not working the first time we try it.

But if these changes are occurred, there should be some video demonstration with the release which explain these changes and the benefit of it.

[jiminy-billy-bob]

These are very good points!