[feasibility check] Victory Heat Rally and other Power Drift incarnations

[saimon69]

Victory Heat Rally - Unofficial spiritual successor to Power Drift gets an early alpha


So my perverse mind was thinking if using a hybrid approach similar approach between Vergeworld Icarus and Drivin'force but with a lesser density of voxels (streets are ramps so no need to plot all voxel pillar unless side of the street) could be possible to have a decent power-drift-like game visually appalling too; to make things more interesting i would also target OCS/ECS

[VladR]

To have some reference comparison point, let's remind us that PowerDrift originated on Sega Board Y : https://segaretro.org/Sega_Y_Board

CPU1 : 12.5 MHz 68000
CPU2 : 12.5 MHz 68000
CPU3 : 12.5 MHz 68000
CPU4 : 4.0 MHz Zilog Z80

GPU: SuperScaler
- 2176 Sprites per frame
- 62.5 MPixels/s fillrate

21 MB RAM for PowerDrift

Now, the question becomes, how much do we need to butcher the Environment to downgrade from 37.5 MHz of 68000 (with a famous SuperScaler) to just 7 MHz 68000.

I think a lot

[VladR]

Now, if we let go of the nonsensical roll rotation/tilt (around the view vector), we can unroll the rendering of all road segments ("voxels").

We'd probably need around 64 such unrolled code chunks, so a bit of Memory would be sacrificed for max speed.

I'm pretty sure that even 7 MHz 68000 could pull such road rendering at 30 fps, at 16 colors.

No idea about on-screen sprites performance on original A500. Is there any scaling HW present whatsoever?
Worst-case scenario, pre-scale all sprites at cost of RAM.

[coder76]

There is no HW-scaling present in Amiga hardware for anything. Although it's fast to scale in y-direction by just skipping scanlines or drawing them twice, the horizontal scaling is difficult to make fast, a lookup table for horizontal scaling is probably fastest, if you want 1x1 pixel quality, but that's not too fast either. Usually sprites are just prescaled for speed in A500 games.

[VladR]

Then I guess all the sprites for current track could be simply pre-scaled at loading time into RAM.


How many KBs (or Width x Height [in pixels]) of 16-color sprites can 68000 do in, say, half frame time ?

[coder76]

The 68000 is not usually used for drawing sprites on screen, as it is slower than the blitter. The blitter can draw around 18 32x32 pixel objects at 50 FPS with 4 bitplanes or 16 colors.

OCS/ECS chipset has also 8 hardware sprites which are each only 16 pixels wide and whole screen height. But if you want 16 color sprites, two sprites must be attached, so you got only 4 sprites now. Due to the limitations of the Amiga sprite hardware, sprites are often only used for player objects and score overlays. Sprites can be reused in vertical direction, so you can reuse score overlay sprites for something else sometimes. Sometimes clever tricks can be done with hardware sprites, like drawing a repeating background by reusing sprite data in horizontal direction. Or multiplexing sprites in vertical direction where possible.

See discussion here about blitter performance:
https://eab.abime.net/showthread.php?t=101707

[saimon69]

hmm i think for the road sprites are not needed, just voxels at the right height, sprites or bobs could be uses for cars and backgroound elements

MAYBE some pseudo rotation could be achieved by tilting the rendering line of the voxels

wish to know how to code an engine like that so to show

[Hewitson]

Check out the C64 conversion of Power Drift. Honestly, one of the best arcade conversions ever in my opinion.