Re: [Plib-users] transparent material with texture ?

[Marc E. <ma...@fa...>]

Steve Baker wrote:
>=20
> Marc Escher wrote:
>=20
> > I'm trying to render an object with a bmp texture (no alpha) and a
> > tranparent material associated to it, but I can't get the material
> > properties to be mixed with the texture. The object is displayed with
> > the texture but with no transparency or any color for the material. W=
hat
> > is the right way to do it ?
>=20
> You are using setColourMaterial (GL_AMBIENT_AND_DIFFUSE) - which tells
> the system to use the *polygon* colour for the Ambient and Diffuse comp=
onent
> of the lighting and to use the setMaterial settings only for the remain=
ing
> components (Specular and Emission).
>=20
> Now, one of the oddities of OpenGL (and hence of SSG) is that the Alpha
> produced by this process is ALWAYS the alpha of the DIFFUSE component...
> which in this case (because of the setColourMaterial) is coming from th=
e
> polygon itself.
>=20
> So, you either need to disable GL_COLOR_MATERIAL so that all the lighti=
ng
> components come from the material settings *OR* put the 0.7 alpha on th=
e
> polygon vertex colours instead of the material.

Right, with these modifications and a few internal bug fixes, it seems
to be working well.
Thanks a lot.

By the way, my scene is composed of translucent and opaque objects that
can intersect each other and I have some problems of drawing order with
the transparent objects. Is there a way in PLIB to manage that ? Can we
enable the GL_DEPTH_TEST for the opaque object and disable it for the
tranparent ones ?


Marc.

--=20
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