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CV Turbo and scaling trees/buildings


Cafeman
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Sorry in advance if this was covered, I searched AA and the net but did not see what I'm looking for.

 

I've been interested lately in how different systems did racing games. Like CV Turbo, 2600 Enduro and Pole Position for example.

 

So how does Turbo manage its huge buildings and trees and "scale" them? My guess, on watching video of it, is that there are actually 3 background screens pre-drawn, and the game quickly cycles through these screens 1-2-3- repeat giving the illusion of scaling. Either that or the CV can handle re-mapping all those tiles/characters in real-time - which seems unlikely.

 

Compare the huge (yet blocky of course) scaling buildings in CV Turbo vs the crappy square "billboards" in Atari 5200 Pole Position! (5200 PP used extra-wide 1-color missile sprites to handle the billboards). I can't think of any 5200/A8 game which has the effect of CV Turbo's huge buildings and trees. Actually, the INTV version of Turbo also does a decent job with screen-filling buildings too, so I assume the 5200 could do this too.

 

Any answers?

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The nametable data can be mapped in different part of the VRAM. So the screen can be build on the 2nd screen before it swap to that one. Usually 0x1800-1AFF(screen1) and 0x1C00-1FFF(screen2) can be mapped. I used double buffering for Flappy Bird. It takes 6 frames to build the screen while the game is running without disabling NMI.

 

I'm thinking Turbo is using a 3rd screen in the unused part of the VRAM. Writing the new value to the nametable register will swap to the other screen. I think it take about 3 frames to load 768 tiles into a nametable.

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I would suggest checking Hang On on Sega Master System and Penguin Adventure for MSX, it's a racing game with a penguin, the 3-D effect is amazing.

 

For Penguin Adventure I suppose every graphic is predefined and screens are loaded and switched in the fly.

 

For Hang On the effects are slightly simpler, only sprites that "grow"

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Penguin Adventure has lush, detailed side-road graphics. They fill the screen impressively, more impressive than the similar CV Antarctic Adventure. But they seem to move and animate a bit too slowly for a Turbo-style racing game, and I doubt the CV could do it as well. I'm unfamiliar with this game ! I watched a long play on YT and it looked very fun, especially the bosses.

 

Master System Hang On has extremely smooth scaling bikes and roadside objects . Are the roadside poles and shrubs and cacti all done with Sprites? Because they scale as smoothly as the bikes and road. However, despite their impressive smoothness, these objects are rather sparse and are small objects , unlike the impressive size of the CV Turbo trees and buildings .

 

So is CV Turbo the only racing game of its era (CV/ 5200/INTV/5200/A8) which has such screen-filling (vertically tall) roadside objects that seem to 'scale' ? Pole Position type games have a flat field but have impressive road edge movement and bigger cars, by way of comparison.

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