Wednesday, October 24, 2012

Rendering Tip - White Walls

Rendering Question - White Walls

Recently on our Forum, we received this query:   

How can I make Walls or other surfaces whiter?
We often get requests for information on how to make walls, ceilings, or objects being rendered look "Whiter".  White Walls and White Backgrounds are often a challenge, because illuminated items in the real world are almost never pure white. Whereas "pure white" is used often in computer images.

Here are some tips. 

White that we see in computer images isn't always realistic 

Some walls in the real world aren't as "White" as we think they are. For instance, if we stood in front of a white wall with a very bright flashlight, would the beam of the flashlight be even "whiter? If it appears whiter, then the wall wasn’t really white but was only perceived as white.

Here is a typical rendering of a room with white walls, illuminated by artificial lights.

It is actually fairly realistic, but often we feel that the walls are just not white enough.

White walls appear gray because they do not receive enough light. However, even if they were "white", we would expect the lampshade to be a brighter white. So, it is primarily a question of white balance. If the walls, floor and ceiling were all "pure white", they would also look the same, leaving no gradient and we wouldn't be able to tell them apart. 

Using a Paint Program

Here I have use a Paint Program to make the walls completely white. This is not really the effect we want either - since both walls are pure white the natural darkening near the corner is washed out.

Brightness Slider

We can make the whole scene brighter with the brightness slider at the top of the rendering window.

Here I increased overall brightness by 10%. This might have made the walls "whiter", but if I ran the brightness all the way up, the rest of the scene would wash out.

Self Glow

Another way to make a single object brighter is to apply self glow to the material on the surface. Self Glow make a material appear brighter - as if additional light was being applied to it.

Here I applied a 15% self glow to both walls. This made the walls lighter, but the automatic "photometric" lighting adjuster darkened the rest of the scene to compensate for the bright walls.

Self Glow and Brightness

So finally, I adjusted the brightness slider at the top of the screen to make the whole image brighter: With a combination of self glow and the brightness slider we may be able to get close to the effect we are looking for.

Lighting Channels

Note: Lighting channels will make this easier - there is one lighting channel that adjusts the self glow with a slider bar, so you can adjust self glow and overall brightness after the rendering is complete. See: Lighting Channels

See also