What is a Copper Chunky2Planar?

[SamuraiCrow]

Copper chunky is separate from chunky to planar.  With a copper chunky you set up a 1 color screen (0 bitplanes) and set up the copper to go as fast as it can and set up the screen as a bunch of copper move instructions to color palette entry 0.  This will allow 12-bit high-color resolutions of 80x256x4096 on ECS and I think 160x256 on AGA.  I'm not sure if the AGA chipset can display more than that but be sure that you don't have the black-border option set or you'll get a black screen.

Chunky to planar routines convert 8-bit chunky to 8-bit planar on the AGA chipset so you get the full resolution displays.  This doesn't use the copper as far as I know.

[SamuraiCrow]

Yes.  Each copper move is an array entry and you can change the colors by changing the color of the copper move instruction directly.  Copper chunky can use the blitter directly to copy sections of the copper list but you must be sure not to use the blitter-based line-drawing instructions becuase there is no way to insure that the pattern draw of the line drawing instructions will be forced to a 16-bit boundary.

Doing chunky to planar may be as easy as using the WritePixelArray8() function in Kickstart 3 but it is typically patched by graphics card drivers so that it will be faster on a graphics card.  The primary advantage of chunky to planar is that it will use the host screen resolution.  Many games use C2P routines becuase copper chunky has such low resolution.

[SamuraiCrow]

You're welcome!  Feel free to look at http://aminet.net/ and search for "copper" to find editors, example source codes, and demos that use the copper to do special effects.

[SamuraiCrow]

With Copper Chunky there is only a limited amount of bandwidth that is available for copper lists while displaying bitplanes but on ECS it makes little difference since there is no additional bandwidth allocated for the copper lists when there are no bitplanes.

Walls1.7 takes advantage of this by displaying 3 bitplanes of screen images overlapping the copper chunky backdrop.  Any more than 3 bitplanes on the ECS chips will cause the blitter to steal DMA channels from the copper and ruin the copper-chunky effect.

[SamuraiCrow]

@DamageX

You must have an earlier version of the Walls demo.  The one I'm referring to had clouds in a copper chunky format.

The point I'm making is that only the AGA version of copper chunky requires all of the bitplanes be disabled because that is the only way to get the copper list to execute in 4x mode timing.

The ECS version of copper chunky has fixed timing for the copper not related to the bitplane usage therefore having some bitplanes active doesn't affect the copper as long as the blitter doesn't have problems accessing its own bandwidth independantly of the display DMAs.

The blitter has more priority over the DMAs than either the CPU or the Copper I think.  It can steal a DMA if there aren't enough for both the blitter and the display DMA.