flimbo's quest dual playfield?

[Raislin77it]

today i've watched flimbo's quest for amiga
it seems it use dual playfield, but with what trick?

it seems 2 layer of 32 colors, impossible even on a 1200.

if i remember well on the c64 the second playfield is faked using a tileset with shifted tiles (like some level of turrican on c64)

but on amiga ? (maybe codetapper have studied the technique)

[Codetapper]

The game is using 5 bitplanes (32 colours), but the actual parallax section of the screen is only 80 pixels high. The game stores a 1 bitplane mask of the parallax section and has to draw the background layer into the gaps of the scenery every frame, since it updates at 50Hz.

[Raislin77it]

Originally Posted by Codetapper

The game is using 5 bitplanes (32 colours), but the actual parallax section of the screen is only 80 pixels high. The game stores a 1 bitplane mask of the parallax section and has to draw the background layer into the gaps of the scenery every frame, since it updates at 50Hz.

i'm really impressed , so every frame almost all the tiles are getting refreshed. the background + the strip for the scroll + the bobs

[Mrs Beanbag]

Originally Posted by Raislin77it

i'm really impressed , so every frame almost all the tiles are getting refreshed. the background + the strip for the scroll + the bobs

it shouldn't need to refresh the tiles, since the background layer only needs to be drawn into the "transparent" parts of the foreground.

i do remember being impressed with it when it first came out, though. it is a neat trick.

[Codetapper]

The game keeps a separate buffer of the parallax section, building that up as you scroll - the only thing it does every frame is the large blit into the gaps when required.

[Raislin77it]

Originally Posted by Mrs Beanbag

it shouldn't need to refresh the tiles, since the background layer only needs to be drawn into the "transparent" parts of the foreground.

The game keeps a separate buffer of the parallax section, building that up as you scroll - the only thing it does every frame is the large blit into the gaps when required.

yes, but are actually a great number of "tiles" to redraw like in this screenshot



very impressive

[Codetapper]

Originally Posted by Raislin77it

yes, but are actually a great number of "tiles" to redraw like in this screenshot

very impressive

In actual fact, there are not many tiles to plot at all. The tiles in the game are 8x8 pixels in size, and 5 bitplanes plus a mask stored after each tile. When you scroll sideways by 8 pixels (over 4 frames), the game has to plot 22 of those tiles, so 5 or 6 per frame.

In addition to that, it has to build up the parallax layer, 80 pixels high therefore 10 tiles have to be plotted into the buffer but this time you have 8 frames to do it as the background scrolls at half the speed. So only one or two tiles per frame need to be plotted.

8x8 pixel tiles are not at all optimised for the Amiga hardware, and it would have been significantly faster if the game had been able to use 16x8 tiles. All tiles are plotted with the CPU.

The real work is restoring the graphics behind each object on the screen, then doing 5 individual cookie cut blits of 320x80 to plot the parallax graphics into the gaps, saving the graphics behind the enemies, then plotting the enemies themselves. The game doesn't have any waits for the blitter in it either.

This bit of code is so tight for time that if you alter the code to plot a 6th
bitplane instead of 5, the game drops to 25Hz with all the enemies flickering. If you wish to see this yourself, drop into the WinUAE debugger (with Shift-F12), type "W 14B7 5" and then "g" to restart. Note that the flickering only occurs when you scroll the screen. It's smart enough to not plot the parallax layer if the player has not scrolled the screen at all.

I should probably create a proper webpage for this analysis on my website too with some screenshots...

[Hewitson]

Originally Posted by Codetapper

I should probably create a proper webpage for this analysis on my website too with some screenshots...

Please do!

[Raislin77it]

Originally Posted by Codetapper

In actual fact, there are not many tiles to plot at all. The tiles in the game are 8x8 pixels in size, and 5 bitplanes plus a mask stored after each tile. When you scroll sideways by 8 pixels (over 4 frames), the game has to plot 22 of those tiles, so 5 or 6 per frame.

In addition to that, it has to build up the parallax layer, 80 pixels high therefore 10 tiles have to be plotted into the buffer but this time you have 8 frames to do it as the background scrolls at half the speed. So only one or two tiles per frame need to be plotted.

8x8 pixel tiles are not at all optimised for the Amiga hardware, and it would have been significantly faster if the game had been able to use 16x8 tiles. All tiles are plotted with the CPU.

The real work is restoring the graphics behind each object on the screen, then doing 5 individual cookie cut blits of 320x80 to plot the parallax graphics into the gaps, saving the graphics behind the enemies, then plotting the enemies themselves. The game doesn't have any waits for the blitter in it either.

This bit of code is so tight for time that if you alter the code to plot a 6th
bitplane instead of 5, the game drops to 25Hz with all the enemies flickering. If you wish to see this yourself, drop into the WinUAE debugger (with Shift-F12), type "W 14B7 5" and then "g" to restart. Note that the flickering only occurs when you scroll the screen. It's smart enough to not plot the parallax layer if the player has not scrolled the screen at all.

I should probably create a proper webpage for this analysis on my website too with some screenshots...

thanks for the explanation, and please if you find time, an article on flimbo's quest is a must

[turrican3]

Flimbo's quest is technically impressive but i don't like the design... But technically it's impressive, too bad that a really graphist didn't work on this one !!! Or perhaps it's just a question of taste ??? Some of you find the gfx beautifull ?? I mean versus agony, it looks crappy for me. ;-)
Like usual don't take it too seriously. ;-)

[seuden]

I absolutely adore this game, the music, graphics and gameplay.

[dlfrsilver]

The graphics of this game are very detailed and excellent. that's one of the best amiga games technically speaking.

[Lonewolf10]

Pfft... based on that screenshot it's truely ugly. Far too purple and green, although it is rather detailed yes.

The 'player stats' portion (bottom of screen) should have much more colour and be more vibrant in my opinion, but no... more dull (but detailed) graphics.

[turrican3]

I played this game a little, i see nothing beautifull.
Technically, it is but the gfx aren't beautifull in my opinion but this is surely just a question of taste.

[Mrs Beanbag]

the fact that the foreground and background both use the same palette gives it quite a cluttered look. it probably looks better in motion, but in any case the purple is quite intense.