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Shadow
Account closed
Registered: Apr 2002
Posts: 355 |
Accuracy in 3d-rotation routines?
How accurate do you run your 3d-rotation routines?
I just started doing a mockup (in a high-level language) for a 3D-rotation routine, but found out that running 8-bit accuracy (8 bit coords and sin/cos tables, 8 bit mulitiplies w. 16 bit result) really looked quite crappy, vertexes flail about rather much. Do people generally run full 16-bit all the way through? |
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HCL
Registered: Feb 2003
Posts: 731 |
@Graham: Yepp, it suxx :/. I never claimed to have a vector shit as good as yours, but 24 bits is pure illness.. One day i might try to keep up with your standards (just ~10 years after), but until then my current vector routine will have to be nice enough.. :). Cheers! |
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Oswald
Registered: Apr 2002
Posts: 5129 |
in 2008 it should be obvious that a 16 bit rotation matrix can be calculated pretty fast:3-4 char high rastertime, and in like half or less time for 2 axes rotation only.
the rotation matrix should be rather viewed imho as the 3 unit vectors which help you make up the coordinates by adding(dividing) them. this can be done even without multiplications assuming no morphing, but precalculated tables for each value used by the coords.
perspective projection must be done with real multiplications. 3d calcs for an avg c64 object should be roughly at 0.5 or 1 frames.
sub pixel stuff is nice, but it doesnt comes through imho at speeds <25 fps.
Id like to see some true vector wolds no matter how slow. tho nobody will code it if I wont :P :) |
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Graham
Account closed
Registered: Dec 2002
Posts: 990 |
@HCL: Well if you need 16 bit rotation, you need a 100% accurate 16 bit matrix too which can only be achieved with 24 bit calculation. Every addition let's you lose 1 bit accuracy and the matrix calculation involves a lot of successive additions. |
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