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Archive Notice: This thread is old and no longer active. It is here for reference purposes. This thread was created on an older version of the flipcode forums, before the site closed in 2005. Please keep that in mind as you view this thread, as many of the topics and opinions may be outdated.
 
dalhia

May 30, 2005, 07:03 PM

What happens when you make two drawPrimitive calls that have an overlapping subset of points? I am using only points (ie point clouds). Do the points of the second call simply replace the previous ones that they overlap? If so, does this happen before it goes to hardware?
Is it worth refilling the vertex buffers to exclude the overlapping points of the first set? Which is slower directx replacing the points or the app (say for a million points)?
Any help would be greatly appreciated.

 
juhnu

May 30, 2005, 09:02 PM

the pixels are possibly rejected in the rasterization stage. It depends if you have enabled zbuffering and the used z-comparison function.

Are your point clouds dynamic and change everyframe? if you can preprocess them you should. If it's dynamic changing data, it really depends on your application being cpu or gpu bound if culling them early by software is of any help.

What are you trying to do exactly?


juhani

 
dalhia

May 31, 2005, 03:29 AM

Well, it is sort of dynamic. They don't necessarily change every frame, but do change with user input. I have a point cloud with up to 8 million points maybe more and it is convenient to highlight a selection by just redrawing the points on top. Its still pretty fast doing it that way and I was wondering why that is the case. It doesn't seem to perform any slower as when the duplicate points are not drawn. If it is reasonable to assume that this will be the case generally I might continue to use this method in other ways as well.
How much does the drawPrimitives call cost? Because I'm essentially calling it twice on a subset of the point cloud.

Thanks for the help.

 
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