[ quesa-Bugs-1227484 ] Add support for OpenGL display lists

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Bugs item #1227484, was opened at 2005-06-25 12:50
Message generated for change (Comment added) made by jwwalker
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Category: None
Group: None
>Status: Pending
>Resolution: Fixed
Priority: 5
Private: No
Submitted By: Michael Sullivan (imikey)
>Assigned to: James W. Walker (jwwalker)
Summary: Add support for OpenGL display lists

Initial Comment:
Was discussed on the list with the following thoughts:

*****

James W. Walker wrote:

 > Yes, but if someone is updating a trimesh every frame (which 
isn"t  
 > an unreasonable expectation) you"ll be compiling a new display 
list  
 > every frame, which will certainly be slower than using the 
current  
 > vertex array path.
 
 I suppose some might do that, but it would not be a concern in 
my use  
 of Quesa.
 
 > To use display lists to their potential you need a geometry type  
 > that"s guaranteed never to change, or some sort of flag for  
 > existing geometries that allows you to declare them as "static"  
 > once their data is set.
 
 It would be easy enough to use an object property as a flag.

*****

Mikey wrote:

 >  To use display lists to their potential you need a
 >  geometry type that"s guaranteed never to change, or some 
sort of flag
 >  for existing geometries that allows you to declare them as 
"static"
 >  once their data is set.
 
 I would think that scenery such as ground terrain, trees, etc. 
would  
 be ideal for using this "static" flag and thus become eligible for  
 storage in display lists.  Furthermore, if all such objects had  
 normals computed for them, then perhaps OpenGL"s built-in 
backface  
 culling could be used when drawing them.


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>Comment By: James W. Walker (jwwalker)
Date: 2007-02-10 21:01

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The new OpenGL renderer uses VBOs when the OpenGL implementation supports
them, and display lists otherwise.

----------------------------------------------------------------------

Comment By: James W. Walker (jwwalker)
Date: 2005-07-16 19:13

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Dair Grant's idea was that we should use VBO's instead of
display lists, as a more modern method. (There has been
some recent disagreement on the comp.graphics.api.opengl
newsgroup as to whether VBOs are necessarily faster than
display lists.)  The trouble with both ideas is that Quesa
currently does its own backface culling. This is to support
the 3 backfacing choices in Quesa, which do not quite
correspond to OpenGL's two choices of two-sided rendering
or not.  But this means that if you moved the camera, you
would have to flush the cached display lists or VBOs.

What we might consider is making a new renderer that
would place less emphasis on compatibility with QD3D
documentation and experience, and more emphasis on
speed.  The new cartoon-style renderer can serve as an
example of how to base a new renderer on the existing
one, rather than writing a whole renderer from scratch.

----------------------------------------------------------------------

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