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Old 14 January 2016, 04:38   #25
Code Kitten

Join Date: Aug 2015
Location: Montreal/Canadia
Age: 46
Posts: 1,064
Originally Posted by eXeler0 View Post
@ReadOnlyCat how was the roto-zoom in Brian the Lion done, and is the technique related to faking mode 7? (Then again I'm unsure if the A1200 and 500 versions were different.)
I do not know.
I have never seen that rotozoom "in the flesh", only on YouTube and I do not recall whether it is AGA only or is supposed to run on OCS. It seems impossible to me to have a full screen pixel precise rotozoom on an A500 unless there are constraints on the structure of the zoomed image which allow for some shortcuts to be taken, like lots of flat surfaces which can be easily blitted while only the contours of the image are really being zoomed.
Galahad seemed to know a few things about this rotozoom so maybe he will be kind enough to share if he reads this thread.

Originally Posted by LuMan View Post
I suppose the real issue would be getting the effect to run at a good speed, while also taking care of the rest of the game code/logic...
This should probably work.
I mentioned earlier that writing the chunky pixels to the copperlist was likely as efficient as determining the tiles to select and send to DMA but it is probably actually even more efficient since it requires only one write to memory and there is no conversion to be done between the mapped texture and the final tiles to send to DMA for copy in VRAM.

So with a bit of luck the Amiga could have a small speed advantage over the console (I say "could" because there are other factors to take into account) in the rendering of the road.

However, where it suffers is the rendering of objects which appear over the road: as I said earlier, using only 4 bitplanes (16 colors) in combination with copper chunky results in zero DMA available for blitting or CPU during the display: only the top of the screen where no road is drawn, the screen borders and the blanking intervals offer free DMA slots for the blitter or CPU. This might be ok for the blitter since the background does not have to be redrawn over the road (the road is drawn using only color 0 by the Copper) and there is no need to mask objects drawn over the road (same reason) but CPU might be a bit tight to texture map the road into the next copperlist and handle game logic under one frame.

This is something I thought about for a future project (yes, I have bazillions of these ) and there are probably some ways to make it fit all under one frame or two but this might not be as simple as I first let it appear.

Note however, that if I recall correctly the thread in which he explains it, gasega68k's routine does not fit under one VBL. This needs to be double checked though.

Originally Posted by s2325 View Post
How about something like Sonic
Drift 1 - 2 for Game Gear? [ Show youtube player ] [ Show youtube player ]
Oh, nice racing game for the GameGear/SMS indeed.
This is more like Lotus II rather than Mario Kart: no texture on the floor except for some road sections in the 2nd installment.
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