[GEM-dev] branches: SIMD & vertex-array going MAIN!

chris clepper cgc at humboldtblvd.com
Tue Dec 14 16:05:19 CET 2004

On Dec 14, 2004, at 3:29 AM, Johannes M Zmoelnig wrote:
> and i have changed the width of all of the arrays to 4 (this is: 
> x/y/z/w but also u/v/0/0) to make them more uniformly.
> probably someone with a good profiler (chris ?) could check whether 
> the performance loss is really that big or if we can accept that in 
> order to be more flexible (esp. in terms of coding as it is so much 
> easier to just have consider one width)

The data is not general enough to be treated this way and it's unlikely 
to save any coding effort for more than the most trivial objects.  They 
don't even have the same ranges for valid data.  For example, vertex 
data is not restricted to any coordinate values, but color info is 
clamped at 1.0, so some sort of scaling would have to take place for 
these to be exchanged (I would say the color info should be unsigned 
chars anyway).  Also, an array width of 3 for normals is not valid 
according to the RedBook, so that is going to require truncation.  
Finally, these objects should have the highest level of optimizations 
possible as dealing with even a 10,000 poly object at a decent 
framerate is going to murder most any CPU.

So my vote is that the array widths should go back to there natural 
sizes as the very minor and rare benefits of equal lengths outweigh the 


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