Am 07.04.2018 um 09:40 schrieb Kenneth:

> Here's the rub, though: If, when originally writing the scene, I imagine that I
> *might* eventually include radiosity, the finish for my sky sphere would be
> easier/more logical to write as...
>                     ambient 0
>                     emission 1.0
>                     diffuse 0
> .... since ambient and emission have the same effect without radiosity. In other
> words, that set-up would appear to be satisfactory for *both* worlds. Yet it
> definitely goes against the (all-inclusive?) argument of not using emission in a
> non-radiosity environment.

Nobody ever said that.

Don't think in terms of "ambient is for non-radiosity scenes, emission
is for radiosity scenes". Disregard whether radiosity is on in your
scene, or whether you ever may want to turn it on. Instead, just
consider what /phsical effect/ you want to model.

The matter of radiosity vs non-radiosity is just the "background story"
of why you should use "ambient" for the one purpose and "emission" for
another.

"ambient" is for modeling the ambient light (i.e. light from the
surroundings) that brightens up the shadows on the object made of that
material. Any regular material should have a little bit of "ambient",
even if you're currently working on a radiosity scene - so that if you
or anyone else ever chooses to use the material in a non-radiosity
scene, the material looks ok out of the box. (Personally, I'm of the
opinion that the "ambient" term should be attached to objects rather
than materials, because it is primarily a geometric property; but that's
the bane of backward compatibility.)

"emission" is for modeling materials emitting light in and of
themselves. Sky spheres are a prime example of this; others might be a
glowing-hot ball bearing or a mage's magic crystal. In a radiosity scene
"emission" is the only mechanism that gives you this result, so you
/must/ use it there; but in non-radiosity scenes you /also/ want to use
"emission" for this purpose, because if you used "ambient" instead, (1)
I'd slap you on the wrist, and (2) you'd have to change the material if
you ever decided to turn on radiosity.


The warning message you get when you set your sky sphere to "ambient
1.0" is to tell you, "hey, you're probably doing something wrong here -
this material looks like you want it to emit light; if that is the case,
you shouldn't be using ambient but emission". It's essentially me
slapping you on the wrist.

Post a reply to this message