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Forums > CSDb Entries > Release id #112378 : Coma Light 13
2012-11-06 21:59
Nightlord

Registered: Jan 2003
Posts: 131
Release id #112378 : Coma Light 13

now that we all had watched this many times, I wanted to ask if the authors can give a bit more info on the technical side of things. The demo has a really entertaining notefile but coders want more detail, so that we know what exactly we need to beat :)

For instance is the shadow casting vector realtime, or the dualpyramid with the 4 circles attached to its vertices. is that realtime?

Thanks again for a great demo.
2012-11-07 06:52
Peiselulli

Registered: Oct 2006
Posts: 81
Axis has programmed this two parts, but as far as I can see, it is all realtime.
2012-11-07 11:27
Mace

Registered: May 2002
Posts: 1799
Yes, please put well commented source codes on Codebase64, please ;-)
2012-11-07 13:02
Oswald

Registered: Apr 2002
Posts: 5017
I suspect Axis is using the sprite priority trick for the shadow vector but am too lazy to check. :)

- one layer of dithered sprites for the new color to show up
- one layer of simple shadow, which trough the priority trick shows the dither layer sprites (only where the shadow is visible)
- use X expanded sprites for bigger layer, each is one color only anyway
- move layers as needed horizontally so shadow fits into them (24 chars)
- change colors by raster interrupts
- 2 color chessboard in charset

very clever :)

same is done in the next part, the twister.


no idea how is the wavy chessboard stuff done, looks like something imported from amiga
2012-11-07 13:23
chatGPZ

Registered: Dec 2001
Posts: 11108
"no idea how is the wavy chessboard stuff done"
FPP+rastercolors. seems one of the easier effects in that demo to me :)
2012-11-07 14:49
Oswald

Registered: Apr 2002
Posts: 5017
yeah, but how do you calculate the shape of it fast enough?
2012-11-07 14:52
chatGPZ

Registered: Dec 2001
Posts: 11108
hu? what shape? you mean the sinus? i'd say thats a table =P
2012-11-07 17:33
Oswald

Registered: Apr 2002
Posts: 5017
sure, 3d rotation calcs are a table aswell. a sinus. thats all.
2012-11-07 22:47
Skate

Registered: Jul 2003
Posts: 490
@Oswald: No, 3d rotation is table lookups+multiplies+additions. This effect is direct table lookups (maybe multiple table lookups). That's why it's possible to do in less cycles than a 3d rotation routine.

Think about a kefrerns bars (or alcatraz or whatever you call it) effect. This effect is as 3d as that one. Better picture now?
2012-11-08 07:04
Oswald

Registered: Apr 2002
Posts: 5017
thanks, I have some vague ideas like that, but no idea exactly how it is done :) probably its like a voxel landscape, here it's only one "ray" sent out.
2012-11-08 07:50
HCL

Registered: Feb 2003
Posts: 716
Exactly, the carpet looks very amigaish, but is probably quite simple. Genius in other words :).

Shadow-vector must have been a pain to code. Even though Axis has done quite a few projecting vectors like mirroring and stuff, this shadow here is also dithered and very big at certain angles. But like Oswald says, perhaps it's possible to draw the shadow as a plain layer with no dithering. By placing a constant dithered layer with highest priority sprites behind the floor, it will become visible when the filled shadow layer (of low-prio sprites) is placed in front of the floor. Still you have to split d025-26 correctly with a f**king cube flying randomly, and we all know Axis hates that ;).

Vector with balls is technically not that hard, but very well executed. We have all seen Reflex do 5 balls, 4 with sprites + one with chars. Here the 5:th ball is replaced with a vector octahedron. I am a bit amazed about the speed of the vector though, as i can imaging putting out those 4 sprite-balls may need quite some timing and stuff.
 
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