Friday, July 25, 2008

Got Distracted

To all of those waiting for STL output, sorry, but I got distracted yesterday and today.  When I was going through the steps necessary for generating tessellated trim surface output I came up with a nice optimization that could apply to both NURBS curves and surfaces.  I won't bore you with the gritty details of the approach.  If you are really interested just drop a comment and I will reply.

In addition to being faster, this optimization uses less texture memory and requires a good deal less setup for generation that the current approach.  It did require modifying every generation shader, but the changes were pretty minor.

I have been reading "Performing Efficient NURBS Modeling Operations on the GPU" repeatedly in order to get prepared for surface-surface intersection.  One of the neat parts of their approach is that their GPU-based generation routines don't have to generate the entire curve or surface but can generate just a sub-region.  They use this ability to iterate through repeatedly (almost Newtonian like) to get within a certain accuracy.  Well, the optimization I put in place lays the groundwork for Wildcat being able to do the same sub-region generation too.  Just need to make a few more tweaks and API changes and we should be all done.

In addition I move to using PBOs to copy curve and surface generation data for server-side generation.  This should be a nice improvement.  I had avoided doing this before because I was running into some driver bugs that would hang the system when I tried to call glReadPixels.

Wow...lots done in the last two days, but little to do with STL.  Getting good STL output really is a priority, I promise.  Hopefully next week.


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