Am 02.12.2010 13:17, schrieb Stephen Klebs:

> This makes the point very clearly. But in the particular example of the
> gradients that for me set this off was that I was trying to deal with a
> completely graphics issue: rgb 0.5 ambient 1. There is no light involved here.
> Ambient is not a real property, it is a completely artificial adjustment control
> that does not exist in the real world. Some of us are not always dealing
> necessarily with how much light is reflected off a piece of white paper in the
> real world. We just want to make a picture by telling POV give me rgb 128.

There /is/ an equivalent to "ambient" in the real world: Ambient light. 
Of course in real life it is not as uniform as in POV-Ray, but that's 
because the "ambient" mechanism was designed at a time where it was 
prohibitively time-consuming to compute ambient light from the scene 
geometry and materials (a process we call radiosity now), so the next 
best thing to do was to let the user decide how much ambient 
illumination looked convincing.

The fact that the ambient mechanism can also be used to create "non-3D 
scenes" like your gradients is just a side effect of it. It's not what 
it was originally designed for.

So yes, there /is/ light involved there. In the POV-Ray render engine, 
there is /nothing/ without light.

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