2 replies to this topic

[jregel]

I've read in the FAQ and technical docs that the object processor can be used to act as a sprite engine, tilemap engine, bitmap display etc.

But how was it used in reality? I've read that Tempest 2000 is basically using the object processor to read a frame buffer for the main display and overlay the score as a sprite.

Did most games work this way (using the Blitter to draw to framebuffers) or was the object processor used in clever ways?

Thanks

JR

[philipj]

My general understanding of the object processor is that a display list is created; the object processor reads this display list and converts the list into graphics by creating two scanlines. When one scanline is created, it shoots the scanline to screen while simultaniously creating the second scanline to be displayed on screen. It's a looping process until there's no more list to display. That's just my understanding of the "Object Processor;" Now as far how Tempest work, you'll have ask someone else about the technicalities for T2K.

[kskunk]

jregel, on Sat Jun 18, 2011 5:05 AM, said:

Did most games work this way (using the Blitter to draw to framebuffers) or was the object processor used in clever ways?

It's probably something like half and half. The blitter is easier to use and capable of more sophisticated graphics, but slower. The object processor is incredibly fast, but somewhat limited in effects and requires more advanced programming, especially in games with a lot of sprites.

Tempest 2K uses the blitter for almost everything. Effects like the smooth shading and 'exploding pixel zoom' can't be done by the object processor. Another hint that it uses the blitter is the framerate. It sometimes dips as low as 15FPS.

Defender 2K uses the object processor for almost everything. This is why the frame rate is a solid 60FPS, even in very frenzied scenes.

Jeff Minter later stated that he was prouder of his work in D2K. While T2K used the machine in straightforward ways (via the 68K and blitter), D2K really squeezed the performance out with some really tricky programming (via the GPU and object processor).

Some other examples:

Val D'Isere Skiing uses only the object processor to achieve such high framerates.
Doom uses only the blitter to achieve realistic shaded 3D effects.
AvP uses a combination of blitter for the 3D parts of the screen, and the object processor for the 2D overlays/maps.

Maybe this gives you some hints to work out which games use which system.

- KS