[osg-users] Is programmable pipeline faster than fixed function pipeline ?

Robert Osfield robert.osfield at gmail.com
Mon Jul 7 01:42:44 PDT 2008


Hi Forest,

2008/7/7 forest37 <forest37 at 163.com>:
>      I know  programmable pipeline  is flexible,but is it faster than fixed
> function pipeline ?

Modern graphics cards don't have fixed function pathways, they just
have stream processors that are programmable.  When you select fixed
function pipeline all you are doing is selecting from a range of
pre-prepared shaders and unfiroms.

This means that the question really is, is the shader you write going
to be more efficient than the equivalent off the shelf one?  Can't
answer this one, it depends on too many things... you just have to try
it and see.

What I can say is, a well shadesr can be allow you to do things that
are impossible with fixed function pipeline, this opens up the
opportunity to implement algorithms that you can't do otherwise, and
these algorithms can be ones that utilise the whole machine far more
efficient - for instance by moving compute work from the CPU to the
GPU.

Robert.



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