Here is a detailed tutorial on how to adjust the white balance of a render in V-Ray using features of the Physical Camera. This will allow you to remove any unwanted colour casting from natural lighting such as the sun or artificial lighting such as an incandescent light bulb.
In photography, when looking at a photo taken from your camera you may notice that there is a blue or orange tint to it even though to the human eye everything looks normal. This is because we are better than the camera at judging what is white and what is not. The blue tint can be a colour casting from the clear sky or fluorescent bulb, whereas the orange tint can be a colour casting from the sunrise or an incandescent bulb.
White balance was introduced as a method to tell the camera what is white within the frame before taking the photo. Then the camera can make a better judgment on what is white and what is not. Most cameras have built in presets for situations such as the ones mentioned in the table above, however in some situations it is best to adjust it manually to get a much better white balance. The process involves adding a neutral reference within the frame that you know is white. Usually this is a portable object that you place in the frame or if you are lucky something already existing in the frame that you know is white. On the camera you can then define the white area by colour picking it.
Setting up white balance in V-Ray
You can use the same techniques used in photography to adjust the white balance in a 3d scene. Place a small white (255,255,255) sphere in the centre of your render. Do not make the sphere so large that it interferes with any lighting you may have in your scene from the sun or interior lights. The sphere must be large enough so that it can gather enough information about the illumination of your scene.
In the V-ray Physical Camera properties set the white balance to neutral, this is pure white. Click render and as the light cache is calculating, enable “show pixel information” in the V-Ray Frame Buffer. There is no need to complete a full render as the light cache will give you enough colour information. Once you start to get a clear image use the right mouse button to click in the centre of the sphere. The RGB value will appear in the pixel information window under colour (8-bit). When picking an area, make sure it is one of the brighter pixels, not one that is black and yet to be calculated by the light cache.
Note down the RGB value. Here is a render before any white balance has been applied. As you can see the walls are very orange.
Switch to the V-Ray Physical Camera. Under white balance you will see a drop down list of ready made presets. These are similar to what you would find on a camera. As we will be adding in our own value, choose custom from the drop down list and enter the RGB value you colour picked from the light cache render.
When entering the RGB value into the custom balance it is best to adjust the colour to be brighter. Otherwise your scene may render a little dark. This method is not entirely accurate due to shadows being cast on to the sphere. Experiment with the value slider to get the correct level of illumination for your scene
The resulting render has no more orange colour casting and it looks much more natural.
Thanks for reading, I hope you enjoyed it. Don’t forget you can share this tutorial with others.