Re: Shadows in Performer 2.0

New Message Reply Date view Thread view Subject view Author view

Angus Dorbie (dorbie++at++bitch.reading.sgi.com)
Fri, 1 Mar 1996 15:31:14 +0100

On Mar 1, 10:02am, Tomas Moller wrote:
> Subject: Shadows in Performer 2.0
> Hello!
>
> I have managed to set up a scene lit by a pfLightSource that cast shadows and
I
> have a few questions.
>
> 1) My shadows are all black. Is it possible to generate shadows with
> transparency so that the object's color on which the shadow is cast will
> be seen through the shadow?
>
> 2) You could set the PFLS_SHADOW_DISPLACE_OFFSET and
PFLS_SHADOW_DISPLACE_SCALE
> for the pfLightSource but I have not found any explanation on these.
> I guess the OFFSET is to be used to avoid self-shadowing. What is the
SCALE-
> parameter to be used for and what exactly to these parameters do?

Look at the manual entry for displacepolygon.

The OpenGL equivalent has two parameters so for info on these look
at the manual for glPolygonOffsetEXT it has bias & offset:
GL_POLYGON_OFFSET_FACTOR_EXT
GL_POLYGON_OFFSET_BIAS_EXT

>
> 3) I also have a problem with transparency. My shadowed model includes a few
> surfaces that are transparent, but when I turn on the shadows the
> transparency disappears. Anyone had similar problems?
>
> 4) The man page says that "shadows and projected textures are not clipped or
> properly computed behind a pfLightSource. Instead, geometry behind the
> pfLightSource will be textured randomly."
> Will surfaces that are outside the frustum of the pfLighSource but in
front
> of the pfLightSource also be "randomly textured"? At least mine are.
> Is it possible to set for example PFTEX_CLAMP or anything to avoid this
> effect?

In IrisGL a TX_WRAP of TX_SELECT is used for this sort of thing,
give this a try.

>
> Thanks,
> Tomas
>
>
> --
>
>
>-- End of excerpt from Tomas Moller

-- 
Angus Dorbie,
Silicon Graphics Ltd, UK
dorbie++at++reading.sgi.com

New Message Reply Date view Thread view Subject view Author view

This archive was generated by hypermail 2.0b2 on Mon Aug 10 1998 - 17:52:31 PDT

This message has been cleansed for anti-spam protection. Replace '++at++' in any mail addresses with the '@' symbol.