Re: pfMaterial

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John Rohlf (jrohlf++at++tubes)
Fri, 23 Dec 94 9:55:50 PST


>
> In my last email I said I intended to override back and front materials
> independently. As always front material overrides work, but after some trial
> and error I can't override the back facing material. I've guessed this is a
> result of the documented limitations of the Iris GL call lmcolor(). I've tried
> both the default pfMtlColorMode() setting on my materials and PFMTL_CMODE_COLOR
> applied to PFMTL_BOTH surfaces.

        You are correct that IrisGL lmcolor does not work for
        back-sided materials so there's no real solution until
        OpenGL.

> I need PFMTL_CMODE_COL for material transparency, which has the side effect of
> disabling colour per primitive information on some triangular meshes I create.
> This is understandable but frustrating because of its requirement for
> transparent materials. A mode where alpha is applied from the material and
> diffuse & ambient from lmcolor would be handy.

        Can you use CMODE_AD and set the pfGeoSets' alpha to that of the
        material? Note that this situation is why we chose to support
        c4f rather than c3f in pfGeoSets.

> Is there a known workaround for my material override, or colour per primitive
> with transparent material problems, or have I miss-diagnosed the symptoms?
> Also, would it be possible for someone to elaborate on what performer is doing
> with materials in "Iris GL speak" to assist my understanding? I've tried to
> glean this information from the manuals but in some respects it's not clear
> what's supposed to be happening under there.
>

        We do nothing special with lighting - a pfMaterial is simply
        a wrapper around GL materials and pfMtlColorMode simply sets
        lmcolor().


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