Re: [Mesa3d-users] GL polygon offset addition

[Taura M <le...@fu...>]

On Thu, 07 Jun 2001 16:36:58 -0600, Brian Paul said:

>  > How would a new glEnable/Disable for this particular attribute of
>  > polygon offsetting be benifit? It seems redundant since the proposal was
>  > to add an option to specify otherwise from the current GL standard
>  > of writing the offsetted depth.
>  
>  Maybe I don't understand what you want.  The change in behaviour that
>  you want (as I understand it) can be expressed by a boolean.  It
>  seems a lot simpler to implement it as a glEnable/Disable() rather
>  than invent a new function which only takes two values.  You'll find
>  that adding a new enable/disable flag is a lot simpler than adding a
>  new API function (consider the dispatch code, display lists, etc).

Oh I understand what yer trying to do now!

I don't think this `sits right' from a design stand point but you obviously
have more experiance with GL.  I've written/designed a lot of libraries myself
and the way I felt was different I guess.


So a new glEnable(GL_POLYGON_OFFSET_WRITE_UNBIASED_DEPTH) it is then,
where it is disabled by default?

Does that sound okay?


>  > For example a wave simulation program, multiple levels of ocean currents
>  > would have to be generated and as waves originate farther from the beach
>  > their interpolation of height may be nearly identical at some points
>  > which makes distinction difficult without polygon offsetting.
>  > 
>  > Also this situation could not be stored in a display list since the height
>  > values are constantly changing.
>  
>  I was assuming that your object/geometry data was stored in a
>  data structure that could easily be traversed and rendered twice
>  per frame (like many OpenGL apps).  If your computation and rendering
>  code are intermingled then a two-pass algorithm may indeed be
>  impractical.  You never explained this when I asked before.

Sorry, i'll be in more depth next time, I didn't want to clutter your
brain with our petty design issues. I know developers have enough in
their brains already. ;)

Yes we do have the drawing routine in a separate itteration function
that we can call with ease and the GL rendering calls outside, the
two way pass can be done... but this program has to run on a variety
of platforms and not all have graphics acceleration. Speed is an
issue so calling the function twice isn't really an option.

-- 
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