[PD] transparency in models

Roman Haefeli reduzierer at yahoo.de
Sat Apr 5 11:09:11 CEST 2008

On Fri, 2008-04-04 at 22:42 -0400, marius schebella wrote:
> Hi,
> I want to apply colors (or textures) with alpha values to obj. models 
> and then turn them around, but I am having problems if I rotate the 
> objects. this actually causes problems with standard geos, too...
> I searched the archives for that problem but I found no real answer. 
> maybe because there is none?

iirc, it was discussed before (otherwise i wouldn't be able to write you
a reply).

from what i understand, alpha rendering depends on rendering order.
first, the textures most behind need to be rendered in order to get
transparency for textures more in front. 

> what is necessary to get transparency working from all different 
> viewpoints?

i don't know if there is a general solution. would be interested as

>  I tried to play around with GEMglDepthFunc and other stuff, 
> but not with the correct result. (correct maybe, but not what I wanted.)
> any help? thanks,

i don't know about [GEMglDepthFunc], but a not very realistic approach
could be to split a model into its planes and change the rendering order
of the planes dynamically, so that most-behind planes are rendered first
and most-in-front planes rendered last. calculating the correct
rendering order needs a lot of math and i don't quit know how to do it.


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