Hi J-S,
Thanks for your detailed answer. Actually, I have been doing quite a lot
of shader work and I wanted to be really sure about this. I was hunting
a bug and therefore I was studying each line of code.
I was pretty sure that the GLSL is not affected by the attribute but I
was wondering if the osg is using it for other purposes.
Btw I am testing for enabled or disabled lights by looking at the values
of the light settings ambient, diffuse and specular. When these are 0, I
skip the light. This way I don't need an extra uniform for
enabled/disabled and it is easy to fall back to fixed functionality.
Also, there is the GLSL variable gl_MaxLights in order to determine the
no of lights. Apparantly, each OpenGL implementation is using 8 as the
max, I have never seen another value... Have you?
Thanks for suggesting ShaderGen to generate the standard lighting
shaders! I was not aware of this.
Cheers
Raymond
Jean-Sebastien Guay wrote:
Hello Raymond,
I have a small question to make sure that I understand the
lighting properly. I am using GLSL to do my lighting and I would
like to be 100% sure that the call
stateSet->setMode(GL_LIGHT0 + id, osg::StateAttribute::ON);
is not necessary for lighting with GLSL. I assume that this call
is for fixed functionality OpenGL only, is this correct? Or is it
used for other purposes too?
You're totally right. When using shaders, you'll need to maintain an
integer count of the number of enabled lights (if you take care to
always group all your enabled lights together from 0) or a bool array
of the state of lights (8 booleans, to say if light at index i [0..7]
is enabled or not).
Then in your shader you need to loop from 0 to 7, check if light i is
enabled, and do the appropriate calculations depending on light type
for that light source.
Or you can do it in some other way, that's just the classic way to
emulate the fixed pipeline.
On this site: http://www.mew.cx/glsl/ you can find a tool called
"ShaderGen" which lets you play with the different features of the
fixed pipeline, and then generates shaders that emulate those
features. You can do some various hand-optimizations afterwards, but
it's a good starting point if you want to see what it looks like.
Hope this helps,
J-S
--
______________________________________________________
Jean-Sebastien Guay jean-sebastien.g...@cm-labs.com
<mailto:jean-sebastien.g...@cm-labs.com>
http://whitestar02.webhop.org/
------------------------------------------------------------------------
_______________________________________________
osg-users mailing list
osg-users@lists.openscenegraph.org
http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
_______________________________________________
osg-users mailing list
osg-users@lists.openscenegraph.org
http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
