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You will find on this blog a collection of my work mostly done in Google SketchUp and Rendered in either Vray for Sketchup, Hypershot, Vray Max, LightUp and Podium.

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Tuesday 3 May 2011

How to use Vray Channels in Vray SketchUp

VFB channels are separate layers saved by Vray SketchUp. The main purpose of this channels is for post processing using image editting software like photoshop that supports layer. These render channels (render elements) serves as layer transparencies that are very useful in selecting certain portion of the image. As we know accurate selection is a must in post processing.

Some of the channels in Vray SketchUp includes:

- Diffuse - The pure diffuse surface color. I will say the positive space
- Alpha - Alpha transparency. I should say the negative space
- Athmosphere -The atmospheric effects. honestly still do not know how this work in Vray Sketchup.
- RGB - this is the render image minus the negative space. This is the RGB color of the Diffuse.
- Reflection - The pure surface reflection before it's multiplied by the reflection filter color.
- Refraction - The pure surface refraction before it's multiplied by the refraction filter color.
- Self Illumination - The self-illumination of the surface.
- Shadow - The diffuse light that was blocked by other objects.
- Specular - The surface specular hilights.
- Raw Light - The raw diffuse direct illumination before it's multiplied by the diffuse surface color.
- Raw GI - The raw diffuse global illumination (not multiplied by the diffuse surface color). Only present if Global illumination is enabled.
- Caustics - The caustics on the material. Only present when the Caustics option of V-Ray is enabled. This channel does not include GI caustics.
- MAterial ID - The material ID of the object.
- Zdepth - The z-depth of the surface.

There are a lot more channels like: Raw Reflection, wire, normals, matte shadow, total lights, bunp normal, RSS, Raw reflection. All of these are design to tweak a particular channel selection during post processing.

I often you Zdpeth Map to simulate the Depth of Field like in the tutorial HERE.

I want to create tutorial on all these channels but perhaps later. For the mentime, I wan to share some of the old resources at Vray SKetchup froum how users use this.

Here is Freeagent approach even with the old version of Vray Sketchup.

Material ID by Andy Orban

Material ID channel tutorial

Having the material ID channel has been an immense help in compositing images in post-process. This is a tool that allows you to mask out a material and replace it with a suitable texture. I thought I would share my steps in making this image using the material ID and Alpha channel.

Step 1. select material ID color. In the material editor, select the material you want to mask, and pick a color other than black. Also, use a color for the diffuse layer that is low saturation, this will be important later.

Step 2. Select the material ID channel in your VFB dialogue. I also have the alpha channel selected since I am putting my own sky behind the image as well.

Step 3. When you render your image, save the image as a “.png”, and you will have three files. Your rgb color map, an alpha map (which is also the transparency in your first png), and a material_id map. (color and material ID shown below:)

Step 4. Open the color and material ID images into your image editor (one that can manipulate and overlap layers or levels) I am using Photoshop, so the rest of this is referencing PS.
Step 5. Select the texture to use as your background and open that in PS as well

Step 6. Arrange the three images so that material ID is on top, then color image is next, and the background is at the bottom of the stack. Make a copy of your color image.
Step 7. Make a selection your material ID color on the first layer by using the “magic wand” tool in PS, set to a tolerance of 5. Then choose the color layer in your layer window and run the following command: Layer -> Layer Mask -> Hide selection.
(If you turn off the copied color layer and material id layer, you will see this:)
Step 8. Make a selection of the black color on the material ID layer. Choose the copy of the color layer in your layer window, then run the following command: Layer -> Layer Mask -> Reveal selection. Next turn off (or delete) your material ID layer. Change the transparency of the copied color layer to “multiply” – this will cover the background with the shadow pattern from the render. If you have a color that is low saturation, the shadows should look fine. If you have a strong saturation, you may need to reduce the saturation on this layer so the colors are more normal. Adjust transparency as needed (mine is at 74%)
Step 9. Create a new layer and airbrush in some shadows under the bushes.


  1. I have Vray for SU version 1.05.30.
    I choose a Material ID in VFB Channel but there is no ID Color under Material options.
    How can I do this? Is there some way around?

  2. oh you need to update your vray. the latest is vray 1.49.01

  3. ok, there is something wrong here...

    I followed the tutorial step by step, but the shadows do not appear over the background. And I dont know why they should appear even in your render.

    @step 8, when I choose multiply, everything that was black in the ID layer gets darker. Nice, but the ID layer doesnt have any shadow info, so why should the multiply command make shadows appear?

    By looking at your own example, there are no shadows in the ID Layer.

  4. ok, I made it work. But there is an error in your tutorial. After several tries, I discovered that at step 8, you must copy AGAIN the green color... not the black color. All the rest is the same. (its over the green color of the ID that the shadows are being cast, so THATS what must be revealed and multiplied)

  5. if you are using shadow, the shadow is included in your diffuse layer. now if there are no shadows being cast in the diffuse then you wont have. so be sure you have elements that are casting shadows...

  6. I had plenty of shadow being cast. Still, the tutorial only worked for me when I copied again the green color instead of the black color.

  7. Hello, I want to know, how works the Wire Color Channel in Vray for SKP (1.49.01). This Channel is more accurated than the Material ID because make an antialiased (at least, work in that way in MAX). Thanks.

  8. it doesnot work that way in Sketchup.

  9. I can also confirm that this does not appear to work for me either (using SketchUp 8 Pro / VfSU 1.49) ......I have shadows in my (very basic) scene, however they are not visible in any of the channels / layers as you have described above. Any chance you might be able to advise or go into a bit more detail in case we are missing something (which is very likely I am sure!).....

  10. Hello, thank you for all the tutorials! Could you reupload images for this tutorial?

  11. Hello! Thank you for all the tutorials. Coulds you please reupload the images in this post?

    1. sorry i think andy removed his images.. let me see what i can do.


Bedroom Interior Rendering

Bedroom Interior Rendering