On Saturday, March 03, 2012 06:41
johannes-bru...@arcor.de [mailto:johannes-bru...@arcor.de] wrote:
Subject: Re: [Opensg-users] ChunkMaterial rendering woes
> I finally got the time to compile your sample.
> As it turns out you have to set the Lit property to true...
Well, this is interesting and unexpected. I was all set to contradict you, but
lucky for me I did some more testing before replying ...
First, my intention is for the shapes to be self-illuminated, not relying on
lights in the scene, and I realized that I had forgotten to turn off the
headlight in the SimpleSceneManager. So I did that first:
mgr->turnHeadlightOff();
I also changed the MaterialChunk to set either the Diffuse or the Emission, but
not both, and to default the other colors. Here is the pattern I'm seeing:
headlight off (no lights in the scene)
Lit = false
Diffuse = red, green blue
Emission unspecified
renders as red, red, red (unexpected)
Diffuse unspecified
Emission = red, green, blue
renders as white, white, white (unexpected)
Lit = true
Diffuse = red, green blue
Emission unspecified
renders as black, black, black (expected)
Diffuse unspecified
Emission = red, green, blue
renders as red, green, blue (expected)
So, setting Lit to true does give the results I would expect. However, I
didn't expect "Lit" to matter when there are no lights in the scene. I
expected that with Lit=false, the shape would simply render with its own pure
unattenuated material color.
Using the VRML lighting model as a guide (
http://www.web3d.org/x3d/specifications/vrml/ISO-IEC-14772-VRML97/part1/concepts.html#4.14
), lighting is "off" if there's no material, and "on" if there is a material,
so interpreting the "Lit" field in the OpenSG material had me confused,
apparently. Thanks for taking the time to set me straight.
The behavior with Lit=false is still unexpected, but I guess I don't care.
I have set Lit=false in other places, but I guess it has always been with
vertex colors rather than material colors.
Cheers.
--
Ted
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