In Blender, it is possible to use non-square textures with simple Box Mapping by enabling the Correct Aspect option during UV unwrapping.
For this to work, a Blender Image Texture node must be selected so that the texture’s aspect ratio is taken into account during unwrapping.
However, since Blender nodes cannot be created directly when using V-Ray for Blender, the current workaround is rather cumbersome: a Blender Image Texture node has to be copied, pasted, and selected specifically for this purpose.
A simpler way to handle non-square textures would be a very useful new feature in V-Ray for Blender.
For architectural visualization, simple Box Mapping is one of the fastest and most efficient ways to generate UVs. Supporting the Correct Aspect functionality (maybe a Button?) directly would significantly improve this workflow.
At the moment Correct Aspect should work you just need to select the bitmap you want to have corrected before unwrapping. We have a “secret” Blender Image node that gets synced with a V-Ray Bitmap if there’s one selected. Unfortunately, I don’t think there’s much we can do about it to make it better.
Basically, you’ve already implemented the feature I was asking for. It just hadn’t worked for me until now.
After your reply, I experimented with it a bit more and discovered that it actually works! The problem was simply my usual workflow.
When I create a V-Ray Image node by dragging and dropping a texture into the Shader Editor, the node has a red outline (meaning it’s selected, but not active). If I unwrap the object immediately afterward, Correct Aspect doesn’t work. However, if I click the Image node again to make it active, everything works perfectly!
When I do the same thing in Cycles, the Image Texture node becomes active immediately after dragging and dropping it (indicated by a white outline in my color theme).
It took me quite a while to notice this difference, which is why I initially thought the feature wasn’t implemented!
So I’d like to revise my feature request: The V-Ray Image node should automatically become active when a texture is added via drag and drop, just like it does in Cycles.
Correct Aspect is already implemented and working correctly!