(help?) Tiles not lining up

[chadderack]

Hi

So I'm having an issue getting a 4x4 set of 16x16 tiles to display
via bitplane pointers (the copper)....

I'm creating a "raw", 4-bitplane image in memory... and I zero everything out. For each bitplane, I'm putting 2 bytes (1 word) of #$FFFF (all bits on) into the image structure for ALL 4 bitplanes.

Apparently each of the bitplanes is offset by 40 bytes ($28) in the source, or it's supposed to be.

I'm expecting to see just black boxes; but there's a white edge on one side and a gray edge on the other side of each block.

Is this because of the background bitplane interacting with the "black" tiles?

ETA: The palette indexes are:

bad white edge: 5
bad gray edge: A
"black": F
brown background: 0



Thanks for any insight.
Chad.

[chadderack]

I tried setting the BG color in the copper to the same "black" (0x111) color, but the bars are still there.

[jotd]

blitter data needs to be 16 pixel wider because of possible shifting

[chadderack]

Originally Posted by jotd

blitter data needs to be 16 pixel wider because of possible shifting

Thanks. I'm just not familiar with the hardware yet.

It seems like bitplanes 0 and 2 align fine and 1 and 3 align fine.
When combining those, they seem to work fine.

But they don't line up vertically. I'm guessing this has something to do with allowing dual playfields?

In my code I'm just going with the one playfield.

The first set of tiles (top) combine correctly to form color #A
The second (bottom) combine correctly to form color #5.



I was thinking it was maybe some kind of minterm... but I'm not using the blitter (at least directly). Just poking the copperlist with pointers.

[Jobbo]

Bplcon1 might be nonzero. This register fine scrolls odd and even planes.

[chadderack]

Originally Posted by Jobbo

Bplcon1 might be nonzero. This register fine scrolls odd and even planes.

Perfect! You're a genius
(so is jotd, but for other reasons--PacMan, etc )

I'm just not as articulate yet with the Amiga. I owe you one!