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.
The problem
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.
The solution
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 and if you have any questions or comments about this tutorial please leave a comment below.
Thanks, Great tip!
Now I got the LWF & White Balance to have a natural color render, Is there other aspects beside them to have a realistic photo?
LWF and white balance are just tools and there are many others. A realistic render comes from your artistic skills as a 3D Visuliser.
Isnt it better to full render frame with that ball inside?
The smaller the render the harder it would be to pick a bright pixel. Best to keep it full size, light cache does not take long to calculate anyway.
The sphere material diffuse color is: 255,255,255?
Yes the diffuse colour is 255,255,255.
Adn what is white balance set in camera when i render 255,255,255 sphere to take RGB sample?
The white balance should be set to neutral before calculating the light cache. Sorry I forgot to add that in to the tutorial, I have now corrected it.
Thank you,
This is my test scene paused at “building light cache”: http://s15.postimage.org/5g1apihrv/LC_paused.jpg
When I zoom on pixels I can see each one with totally different color. How to pick up proper one for color balance?
http://img269.imageshack.us/img269/583/lcsphere.png
Pick one of the lighter blue pixels. Since blue is the prominent colour casting on your objects.
A nice simple tutorial! I think you should show a render of it with the white balance on neautral though, so everyone can physically see what you mean. Some beginners might not fully understand the difference without a visual representation.
Thank you Andy. I have updated the tutorial to include a render before any white balance has been applied.
Thank you,
To make it in less steps maybe it would be good idea to stop LC at neutral color balance, than set camera color balance to custom, click color, pick color picker and pick it up straight from LC. Right?
The process is: Add a white sphere, set camera white balance to neutral, render LC and colour pick, set camera white balance to custom and add in the picked colour.
Yes, but why to launch Pixel information an dnote RGB numbers if You can click on color swatch color balance) use its color picker to pick it straight from LC?
This is what I try to descride (sorry for my english, delete it if You want, I dont want to make mess here)
http://s18.postimage.org/cio1dx7s9/LC_color_picker.png
Yes you could do it that way if you like. However there are some custom colour swatches out there that do not have the option to colour pick.
Nice tut James, Solid Rocks is becoming less useful the more I learn about VRay from your site.
Thanks James, great tips!As well as all your other tutorials.
nice tip but why you donot crop scene ( the sphere) for fast rendering and then pick RGB
You could crop the render, but I don’t think this will save you much time. Depends on your scene I guess.
nice and simple.should we do this test only after placing all the light sources with final settings of each parameters of them?
Yes, do this at the end of your workflow.