John Rohlf (jrohlf++at++tubes)
Tue, 1 Mar 94 13:41:36 PST
1.2 Performer supports the following GL concepts:
1. Texture idle through pfIdleTex()
2. Query whether a texture is loaded or not through pfIsTexLoaded()
Other GL features such as subtexload will be supported in the
release following 1.2 which will be OpenGL based. Expect
sophisticated texture management in 1.3 or 2.0 or whatever
we call it.
> - For managing the pfLayer i read that Perf1.2 uses
> DisplacePolygon, but if i well remember displace polygon modify the Z
> value of a polygon by a factor calculated by the use of the polygon
> orientation, and this factor is 0.0 if the polygon as its normal oriented
> direct to the viewer.So for coplanar polygon in front of the viewer it
> will no works fine
> Is'it right ??? Is there a way to avoid this ???
This is a correct evaluation of a fundamental flaw in displacepolygon().
The OpenGL version will solve this problem by adding an offset
in addition to the scale. Remember that you can use stencil-based
decaling in Performer by calling pfLayerMode(layer, PFDECAL_BASE_STENCIL).
We may even change the default back to stencil since many people
have had problems with displacepolygon-type decaling.
> - Is there a way to store informations on every nodes of the
> hierarchy ??
In 1.2, all libpr and libpf objects including nodes have a
data pointer accessed through pfUserData. Thus you can attach
the structure of your choice to any object.
> - I heard that Performer sorts the polygons before the drawing to
> optimise the graphics (Especially mode transitions).But what kind of
> sorting Performer uses .. Is it only to group polygons with the same
> textures to avoid Texbind ???
We have a sorting hierarchy that includes sorting by texture
but we also sort by matrix, by material, and by transparency.
The sorting hierarchy may differ between machines and releases.
> - My last question is not especially for Performer guys, in fact
> it seems that the GL call "msmask()" is very slow . Is it right ???
I don't know. We use msmask for fade LOD and it doesn't seem
to be very slow. Of course the term "slow" is relative to the
number of times you call it per frame.
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