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index on index buffer?

Started by yuppies Nov 6, 2004 at 4:23 AM 5 replies 950+ views

Original Post

Nov 6, 2004 at 4:23 AM

im just curious why DirectX index buffer only accepts short values for specifying the index? ive tried using an integer array for specifying index but it doesnt work., then finally i consult some tutorials and all of them are using an array of short for indices, whats the logical explanation for this? pls enlighten my innocent mind..

j-ho

Nov 6, 2004 at 4:51 AM

the 3rd (format) parameter can be D3DFMT_INDEX16 or D3DFMT_INDEX32

That should sort you out :)

Namethatnobodyelsetook

Nov 6, 2004 at 9:26 AM

99% of cards in use don't support index32. For nVidia, upto and including GeForce 4 doesn't have index32. GeForceFX may, I'm not sure. 6800/6600 probably does. As for ATI, I'm not sure when they added index32 support.

WarAmp

Nov 6, 2004 at 11:28 AM

16 bit indices are used because
A) It's rare to have more than 65536 vertices in a vertex buffer.
B) With 16-bit indices, the driver can pack both into a 32 bit word and transfer 2 indices across the bus at once. So its a bandwidth savings.

dxdotnet1

Nov 6, 2004 at 9:17 PM

cool.. thanks guys

Supernat02

Nov 6, 2004 at 9:52 PM

You said that you tried integers. A common mistake (without even thinking about it) is to use int instead of unsigned int. You may see some tutorials that use DWORD.

Chris

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