On Tue, 06 Sep 2005 19:57:32 +0200, Christopher Sean Morrison <brlcad@...> wrote:
> The light shader is indeed where you go to create/set lights. If
> there are no lights in your scene, the raytracer creates a couple
> default lights for you just so you're not looking at a black window.
> Once you create a light, however, they will override the default
> lights and you'll be able to position the lighting exactly as you
> want it.
Ah, that explains it. With two lights overhead the candle became a lot
> The lights are oriented at
> the origin by default, so if you want different directional lights or
> want to change their intensity, you'll need to edit the light
> parameters on the combination editor's shader panel. Fraction will
> control the intensity (lumens is used by the photon map renderer).
I tried to set the fractions so they added up to 1.0. That gave a
rather dull flame! In fact, the candle itself was brighter just below
the flame. It seems like the flame is emitting little light towards
the eye, and it is reflecting little light from the other sources
because of the surface orientation.
I then increased the fractions. Values like 10 made everything appear
white. 1.0 for each light and 1.1 for the candle gave tolerable results.
But still the flame is rather dark around the edges. It does not look
like a flame.
Thinking aloud... To look like a flame it would have to be transparent.
The invisible setting comes to mind :) The flame should be nowhere
darker than its background. There should not be an issue with
surface angle relative to viewing direction. Is this the reason
for the dark edge?
Perhaps I will experiment wiht a smaller light source at the center
of the flame, and some combination of transparency and other effects
for the flame itself. But I remember tinkering with OpenGL and finding
that the lamp became black when the only light source was inside the
sphere, until I found I could change the sign of some parameter to
make it "reflect" the light inside from the "wrong" side ot the sphere
Why is it called "fraction", would not "brightness" be a better
incdication of what you get from this parameter?
I then tried the photon emission, oh boy, that takes a long time.
But the black edge around the flame is gone.
Are the various lighting models described somewhere? If not, would
it be usefull if I summarize what I learn from you and from
experimenting, I mean, would you include it in the docs somewhere?
> "Infinite" lights are lights used to simulate high intensity lights
> that are far away (e.g. simulating sunlight). The main effect is
> that they cause hard shadows but don't necessarily affect intensity
Shadow??? There's no shadows here - Eh, yes there are, but why are
they only on the curved surfaces, not on the table.. Oh, I see,
the checker shader does not support lighting at all, it just smears
a fixed pair of colors.. How does this shader know which surface
to give the checkerboard pattern , and which surface to make with
thin slits? Does it look at the angle with the z axis? I should
experiment a little and not bother you with so many questions..
Should I write a minimal description of the various shaders? Or is
there already a documentation that I have overlooked?
Thanks for you many, and very helpfull answers!