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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.
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chatGPZ
Registered: Dec 2001
Posts: 11089 |
"no idea how is the wavy chessboard stuff done"
FPP+rastercolors. seems one of the easier effects in that demo to me :) |
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Oswald
Registered: Apr 2002
Posts: 5017 |
yeah, but how do you calculate the shape of it fast enough? |
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chatGPZ
Registered: Dec 2001
Posts: 11089 |
hu? what shape? you mean the sinus? i'd say thats a table =P |
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Oswald
Registered: Apr 2002
Posts: 5017 |
sure, 3d rotation calcs are a table aswell. a sinus. thats all. |
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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? |
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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. |
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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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Bitbreaker
Registered: Oct 2002
Posts: 498 |
It is an FLI done each second line to force a new charset and screen to be loaded and not to stretch the dithering what would happen on a per line update like with FPP. Also the stuff is interlaced by using two banks. During FLI the z-tab is cleared to have a bit more time for generating a new one and be able to load the next part (Mostly this part was thought for bootstrapping the second side)
The z-effect is done by creating a z-tab, by starting with the deepest z-value and just writing the y-positions from a sine-table (higher z-values by that overwrite lower ones and thus lower parts get automatically hidden). Z thereby determines x-size of the chessboard that is represented via the FLI, as well as what colors that are set for the multicolorcharset (be aware of gray dots, YUCK). So for the white parts of the chessboard colors are changed interleaved, while the blue parts just fade from blue to black (multicol 3 -> colram), as else one would run out of colors.
Basically one can put any bitmap-texture on all that, but there are some caveats with the color-interleaves and horizontal lines that appear very stretched.
That is how the texture looks like before it is split up into 2 line high blocks and converted to the respective charsets + screens:
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Oswald
Registered: Apr 2002
Posts: 5017 |
checked again the cube shadow, maybe I was thinking too much into it, as the cube and the shadow can intersect heavily, that would cause big headaches with sprite layer tricks.
it's not a huge problem to draw it entirelly either tho. probably axis is being clever the other way round, and only updates what needed & to have the shadow intersected by the chessboard its not much extra stuff having to plot into the eor buffer, you can speedcodize the chessboard lines plotting lda sta sta sta sta style. even pick only the lines that have to be redrawn.
edit: or, setup the eorbuffer with the chessboard lines, then draw/erase the shadow lines with eor, only fill out what needed and done. |
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Oswald
Registered: Apr 2002
Posts: 5017 |
thanks, I get the chessboard stuff now, it helps a lot also that there are only 100 lines to calculate :) thats a cool cheat as its not visible at all. I guess it wouldnt look 5% nicer if all 200 lines were done. |
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