Quote:

ppcamiga1 wrote: "stop this crap it will be always too slow"

said pepikamiga1's father
as he was coming out of his mother's cervix

_________________
I HAVE ABS OF STEEL
--
CAN YOU SEE ME? CAN YOU HEAR ME? OK FOR WORK

New experiment with PTDQ: dual playfield with both layers scrolling freely.

https://www.youtube.com/watch?v=mENnJygi5Eo

As usual, available from https://retream.itch.io/ptdq.

Fun fact: the foreground layer is triple-buffered, but that's a complete waste as no graphics rendering is performed; the reason is that the initial 5% was made months ago, but I got around to make the rest only now that my right arm is immobilized due to injury: it was just too much of a chore to write more code and to create more assets using just the left hand - and I'm not even left-handed (even just typing this is driving me nuts)!


LAYERS

Common:
* PTDQ system
* RGBWa color model
* 320x256 visible dots
* interleaved bitplanes
* horizontal and vertical scrolling

Background:
* 336x336 dots
* maximum 256 colors

Foreground:
* 672x576 dots
* maximum 81 non-transparent colors
* triple buffer


NOTES

* Both the layers reside in CHIP RAM.
* The layers use 6 bitplanes in all.
* If the foreground had not used 100% transparent dots, its maximum number of colors would have been 256.
* The foreground mode is changed by writing a whole 24-bit palette to the COLORxx registers with the CPU during the vertical blanking. The required palettes are pre-calculated at startup.
* The CPU is idle most of the time. The Copper is idle most of time (but if the staggered lines are on, it performs a wait and a write for each visible rasterline). The Blitter is idle.
* The triple buffer was implemented for glitchless rendering of graphics, but eventually no rendering was added.
* YouTube's encoding degraded the quality.

Last edited by saimo on 09-Feb-2026 at 10:38 AM.
Last edited by saimo on 05-Feb-2026 at 05:32 PM.
Last edited by saimo on 05-Feb-2026 at 05:29 PM.

_________________
RETREAM - retro dreams for Amiga, Commodore 64 and PC

I pushed the dual playfield a bit further: 256+256 colors, plus 8-bit alpha per color component value, plus 2-bit alpha channel.

https://www.youtube.com/watch?v=aHwE41IWmQ4

LAYERS

Common:
* PTDQ system
* RGBWa color model
* 320x256 visible dots
* interleaved bitplanes
* horizontal and vertical scrolling

Background:
* 336x336 dots
* maximum 256 colors

Foreground:
* 672x576 dots
* maximum 256 colors
* 8-bit alpha per color component
* 2-bit alpha per pixel

NOTES

* Both the layers reside in CHIP RAM.
* The layers use 8 bitplanes in all.
* The foreground mode is changed by writing a whole 24-bit palette to the COLORxx registers with the CPU during the vertical blanking. The required palettes are pre-calculated at startup.
* The CPU is idle most of the time. The Copper is idle most of time (but if the staggered lines are on, it performs a wait and a write for each visible rasterline). The Blitter is idle.
* YouTube's encoding degraded the quality.

New demo available at https://retream.itch.io/ptdq as usual.

Last edited by saimo on 09-Feb-2026 at 10:37 AM.
Last edited by saimo on 08-Feb-2026 at 12:40 PM.

_________________
RETREAM - retro dreams for Amiga, Commodore 64 and PC

Since the last demo reused the graphics of the previous one (with improved quality and additional effects, thanks to the extra alpha channel), the latter didn't look that good anymore, so I decided to rework it to produce a more meaningful and interesting result. I just released it, so who wants to try in on their machine can get it from https://retream.itch.io/ptdq as usual.

https://www.youtube.com/watch?v=1eBPcg1ndXY

LAYERS

Common:
* PTDQ system
* RGBWa color model
* 320x256 visible dots
* interleaved bitplanes
* horizontal and vertical scrolling

Background:
* 336x272 dots
* maximum 256 colors

Foreground:
* 672x576 dots
* maximum 81 non-transparent colors
* 8-bit alpha per base color

NOTES

* Both the layers reside in CHIP RAM.
* The layers use 6 bitplanes in all.
* If the foreground had not used 100% transparent dots, its maximum number of colors would have been 256.
* The foreground mode is changed by writing a whole 24-bit palette to the COLORxx registers with the CPU during the vertical blanking. The required palettes are pre-calculated at startup.
* The Copper is idle most of time (but if the staggered lines are on, it performs a wait and a write for each visible rasterline). The Blitter is idle.
* The texture is 512x512 dots and gets scaled and rotated onto a triple-buffered 128x128 dots raster.
* The raster gets rendered onto the foreground while racing the beam by means of PTDQ_DoC2P_R() when, at the end of a frame, it is found to have changed (so, at most 50 times per second, even if the fps limit is off).

PERFORMANCE

On a stock Amiga 1200, the speed is about 17.5 fps.
On an Amiga 1200 equipped with a Blizzard 1230 IV mounting a 50 MHz 68030 and 60 ns FAST RAM, the speed varies between 80 and 94 fps.
The fps fluctuation depends on the fact that the fetching of the texture dots is more of less friendly to the CPU data cache according to the scale factor and the rotation angle.

Last edited by saimo on 03-Mar-2026 at 09:36 AM.

_________________
RETREAM - retro dreams for Amiga, Commodore 64 and PC