Re: Billboard Performance
Alejandro Saez (cano++at++krusty.engr.sgi.com)
Thu, 23 Oct 1997 13:38:03 -0500
On Jul 29, 10:44am, Charles Paik wrote:
> Subject: Billboard Performance
> I have a database full of trees. In fact, the trees are taking up more than
> 50% of the time to render the scene. The trees are not modeled as
> billboards. Can I get significant performance increases by changing my
> database to model the trees as billboards?
>
> -or- Are there any good suggestions on improving performance when
> you have to render a ton of trees?
>
> --
> Charles Paik
> charles.c.paik++at++boeing.com
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>-- End of excerpt from Charles Paik
How are you representing trees now? I'm assuming you are using a 3D solid model
of a tree, and with that in mind the answer, most of the time is yes but then
you should ask where is that 50% of time actually being spent. Using billboards
has a trade off, in one hand you are most probably reducing the number of polys
being drawn (how many triangles has a modeled tree, 50-100? a billboard will be
2 traingles or a quad)
which is good for the draw stage but then you are adding an extra burden to
your app because you have to compute the orientation ot the billboards. If you
have plenty of time left in your app. and it is also geometry limeted then
probably billboards are the way to go. There is still another way of lightening
the draw stage by using LODs for the trees, this is also adding extra app time
to compute the correct LOD. Another thing to consider is .. are you cloning a
single tree. if this is the case then bear in mind that each cloned tree has a
translation matrix associated that must be computed for each tree, if this is
your case then try copying at an extra memory consuption fee.
--
------------------------------------------------------------------------
Alejandro Saez
Software Engineer
Silicon Chile S.A.
Avda. Santa Maria 2560
E-mail: asaez++at++silicon.cl Providencia
Phone: +56 (2) 203 3371 Ext. 107 Santiago
Fax: +56 (2) 203 3370 Chile
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