Join Brian Bradley for an in-depth discussion in this video The wrapper material, part of SketchUp: Rendering with V-Ray 3.
- [Instructor] Because V-Ray for SketchUp Version 3 was still in beta when I recorded my controlling color bleed in V-Ray for SketchUp course found here on lynda.com, one of the items that I missed out but that I'd covered in other DCC applications using V-Ray was the wrapper material. As this is now available with all of its functionality intact in V-Ray for SketchUp, I thought it would be nice to quickly revisit the color bleed topic and use it as a means to take a look at the wrapper materials controls in a practical setting.
To do that with our baseline render already added to the frame buffer's history list, let's add a wrapper material. With it selected, we see that we have quite a number of controls available that can help us handle both the surface and matt properties of objects in our scene with the ones we are interested in being the generate and receive GI options that we see sitting right at the top. We do have this GI surface ID option available but this is really for preventing the blending of light cache samples across different geometry surfaces.
As the Chaos Group documentation says if two objects have different GI surface IDs, the light cache samples of the two objects will not be blended. This can be useful for preventing light leaks between objects that are receiving very different levels of illumination. To use the wrapper material on our floor geometry, we will need to first of all access the base material dropdown and choose the material currently assigned to the floor which in this instance is the wood floor option and then of course assign the wrapper material itself to the floor geometry.
If were to go ahead and render now, we would see that without adding any tweaks to the material, nothing at all would have changed in the scene. In order to make certain that we understand just what these GI options do then, let's make a couple of test renders. With the generate GI option set at zero or turned off then, what we get as we render is an image in which our red floor material is contributing no GI or light balance to the scene. The other materials are of course still generating GI which is why we still have a measure of white balance although we have as you can see dropped our illumination levels by quite a bit.
Let's save this render to history and try another, this time with just the receive GI option turned off. Now, of course, in the light cache pre-calc phase this may look like a useless option as we now have a completely black floor. What we need to keep in mind though is that the light cache pre-calc phase is only showing us the GI calculations currently taking place. Once the actual render kicks in, we can see that we are still getting some color information from the floor material. Of course, the question you are probably asking is how these options may be able to help with color bleed problems? Well, looking again at the render we saved with the generate GI control disabled, we can perhaps see that with a tweak to our camera's exposure settings, we could actually create a render that has no color bleed coming from the red floor material at all.
Perhaps a better option though if I just turn the receive GI option back on, would be to use a generate GI value of 0.25, rather than disabling it altogether. This would mean that our floor would now be adding just 25% of its total possible light balance to the scene. We could then dial in an exposure compensation by setting our camera's exposure value to something like nine and as we take a final render, and compare to our initial or base image, we can see that by using the controls on the wrapper material, we have been able to quickly and easily reduce color bleed in the scene.
- Gamma handling in V-Ray 3 for SketchUp
- Working with interactive rendering
- V-Ray light types
- Working with irradiance mapping
- Rendering animations
- Working with the V-Ray camera
- Using the Materials UI
- V-Ray FX tools
- Stereoscopic 3D rendering
- Using V-Ray objects