Material library and UV size

[aleksey_dremin]

When importing a model with UV map to SketchUp, whether it is a regular import via *dae or any other format via Transmutr, the texture size in the Materials/Edit/Texture tray is equal to one inch, i.e. 25.4 mm.
When I save a material in the V-Ray library, when using it in a new project, the texture size increases to 10 inches, i.e. 254mm. this either produces duplicates of materials, or you need to manually reduce the size.
How do I configure the V-Ray library to open materials with a texture size of 25.4 mm?

[aleksey_dremin]

Ok, the Transmutr developers adjusted the input size to 254 mm, so there is no problem.
Although if you save the material to the VRay library, it will not remember the texture size, color, or transparency level when it is loaded. And if you save the material using the native SketchUp method, all this will be done ( just like when copying a customized model). It would be great if you removed these restrictions.

[Peter.Chaushev]

Hello, Aleksey,
Apologies for the late reply!

SketchUp's internal scale is always set to 1". This is the size a V-Ray material's textures will assume if no object UVs are set.
In the illustrations below I've only used a procedural V-Ray Checker texture in the Reflection slot to simplify the example:


V-Ray assumes object UVs in SketchUp from the texture projected on each object face in SketchUp. This means UVs are only available when the material in SketchUp uses a texture (corresponding to the V-Ray Diffuse texture slot).
For nested and procedural textures or when a material lacks a Diffuse texture a couple of options are offered in the "Binding" section of the V-Ray material settings. There, you can either select a custom Bitmap texture or use the generic "Texture Helper". Using any of those options allows adjusting the UV size based on the SketchUp texture size. The default texture size in SketchUp is 10" or ~0.25m

UVs are part of the object properties, not materials'. This is why despite the peculiar way SketchUp's texture projection works V-Ray materials cannot store the data of UVs from SketchUp.
Furthermore, you may notice some of the V-Ray library materials have a dimension at the end of their names. It serves as an indicator of the suggested UV size that needs to be manually set:


There is one way to modify the UV size of textures in V-Ray in a relative way regardless of the UVs used. You can find all controls in each texture's "Texture Placement" section:


Hope this helps!

Kind regards,
Peter