🚀 go-pugleaf

In <7671@dove.nist.gov> fred@poly2.nist.gov (Frederick R. Phelan Jr.) writes:
>Suppose you have a material color:
>float object_color[] = 
>{
>        DIFFUSE,    0.1, 1.0, 0.2,
>        SPECULAR,   0.3, 0.9, 0.3,
>        EMISSION,   1.0, 0.1, 1.0,
>        SHININESS,  24.0,
>        LMNULL 
>};
>which has been set with:
>	lmdef(DEFMATERIAL, 1, 15, object_color);
>First, are you allowed to change the EMISSION values (or really any
>of object_color's properties) on the fly?  

Yes.  Use lmcolor(LMC_EMISSION) if you are only changing that one
property, and use c3f() or cpack() commands to change it.

>Second, If you can change on the fly, do you need to do a new call to
>lmdef every time for the changes to take effect or is the first call
>sufficient?

Changing the value in the array is not sufficient-- you need to send
the values to the GL.  Use lmcolor() if you can, or just issue another
lmdef() with just the values you are changing:

float object_emission[] = { EMISSION, 0.2, 0.5, 0.1, LMNULL };
lmdef(DEFMATERIAL, 1, 5, object_emission);

In OpenGL, this is much simpler-- material properties are just like
colors.  You set them and forget them.

So, in OpenGL, your code will look like:

float emission[3] = { 1.0, 0.1, 1.0 };
glMaterialfv(GL_FRONT, GL_EMISSION, emission);

... no bind necessary.
--
--gavin     (gavin@sgi.com,  (415)390-1024)