bitplanes

This was using existing blitter mask bitplanes so there was no sprite creation, everything was very fast (assembly).

Later Amigas had new graphics modes, and Intuition had support for 8 bitplanes from the beginning.

On Amiga, one had to use bitplanes which killed performance unless one could use the Blitter.

The spirit of the project, however, was to emulate the tricks that bitplanes made famous.

If you're willing to do your own timing and race the beam, pump $0RGB values to $DFF180 with no bitplanes enabled at all.

It was a great addition that extended the existing idea of bitplanes, which was a really good one in lots of ways though.

They had 8 primary colors (Black, Red, Green, Blue, Cyan Magenta Yellow White) in three bitplanes that would get OR-ed together.

So you could do all kind of nifty tricks, like changing the colors of your 5-bitplanes (32 colors) between lines, creating an image with much more than 32 colors.

Of course the very thing made genlock work so well on the Amiga (the use of bitplanes) was a factor in the ultimate demise of the Amiga in the 1990s.

The planar bitmap model had worked ok on the older models with a maximum of 32 colors (5 bitplanes), but with 256 colors you had to do 8 writes to set a pixel.

(That was one usual arrangement, but there are other options - e.g., interleaved bitplanes and/or no video RAM as such.) Separate bitplanes were very annoying in many respects, and the demise of the approach was probably regretted by only a few.

Conveiently, at the default hires (640x horiz resolution) 68k cpu would always be able to access chip ram, as the cpu is only able to use half the cycles, and at 4 color the blitter in Agnus uses most of the other half to stream bitplanes to Denise.

Or you could make 1bpp "control" bitplanes that, when fed to the blitter, would fill your polygons scanline by scanline.

Glenz vectors: use blitter to draw lines & blit into bitplanes with polygon filling mode, you'd need at least three bitplanes, one for the silhouette of the shape, one for the front-facing faces and one for the back-facing faces, then set up the palette so it's "just right" for the combination of planes to give a semi-transparent effect.