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Is rotation possible on nes?
http://forums.nesdev.com/viewtopic.php?f=2&t=16365
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Author:  tepples [ Wed Aug 16, 2017 12:41 pm ]
Post subject:  Re: Is rotation possible on nes?

By "4 sprites", were you referring to four 8x8, 8x16, 16x16, 16x32, 32x32, etc. portions of the same cel, or were you referring to four independent cels? If four independent cels, then all four would need to be rotated by the same angle, and I fail to understand exactly how this would prove useful. If four portions of the same cel, you'd need to somehow combine them into one cel after you have finished rotating them so that you don't have a bunch of blank space at each side that decreases usable overdraw. If you do not understand how rotating four cels would result in a bunch of blank space at each side that decreases usable overdraw, do you need me to make you a diagram?

Author:  rainwarrior [ Wed Aug 16, 2017 3:56 pm ]
Post subject:  Re: Is rotation possible on nes?

tepples wrote:
By "4 sprites", were you referring to four 8x8, 8x16, 16x16, 16x32, 32x32, etc. portions of the same cel, or were you referring to four independent cels? If four independent cels, then all four would need to be rotated by the same angle, and I fail to understand exactly how this would prove useful.

I'm pretty sure he meant independent cells.

I think it's presuming an advantage for addressing texel fetches at a per-byte level, and from that premise if you're wasting a whole byte per texel you might as well stack 4 images in the same space, I guess. If you did want to rotate all 4 by he same angle at once, I would think that's an advantage too, albeit a very situational one.

For instance, if you were doing a Sonic the Hedgehog rotating bonus round as sprites, you could rotate a set of 4 different tiles all at once.

Author:  psycopathicteen [ Wed Aug 16, 2017 4:03 pm ]
Post subject:  Re: Is rotation possible on nes?

If you're using the RAM filling method, you can fill RAM 4 times faster. If you don't need 4 sets of sprites at once, you can do two sets of sprites at both 0 and 90 degrees.

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