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Shadow
Account closed
Registered: Apr 2002
Posts: 355 |
'HCL-plasma' - how does it work?
That fullscreen-fast-plasma-thing that we saw quite a few versions of in Edge Of Disgrace (with sprite zoomer on top, in sideborder, with techtech etc.) - what's the theory?
It is pretty obvious from speed and size that it is not done using per-pixel-code...
My theory was that it was done using FPP-technique, ie. we have a base-plasma-picture, and then by displaying cleverly chosen lines from this base-picture we get the plasma.
I did some prototyping on PC to test this theory, but I can't get anything that looks correct. Am I barking up the wrong tree here? |
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Oswald
Registered: Apr 2002
Posts: 5094 |
Quote: Yepp, shit like that always happens. When you reach a certain level of popularity, people will start giving you credit for stuff that others made.. That also happens to Graham. e.g. the all-border sprite-zoomer from ComaJob, which ppl think is Graham's invention, but just look at this.. Fierce Creations or was it Design Overdose. And many more examples in *real life*(tm).
was there an fpp plasma before graham's one ? |
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Cruzer
Registered: Dec 2001
Posts: 1048 |
Shadow: You also might wanna "cycle" the colors, i.e. have a constant that you add to the sine values, which is incremented for every line in the generated pattern. Anyway, experimentation is the way to go for getting the plasmatic feel. It usually takes a lot of trial & error before it looks good.
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HCL
Registered: Feb 2003
Posts: 728 |
Quote: was there an fpp plasma before graham's one ?
No, but a sprite-zoomer. |
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Shadow
Account closed
Registered: Apr 2002
Posts: 355 |
Aha! So the base-picture IS recalculated each frame, no wonder I couldn't get it to look right! |
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Testa
Account closed
Registered: Oct 2004
Posts: 197 |
Quote: How a simple version works:
step 1: have an FPP routine of your choice. It's gonna need to be sprite FPP if you're in the borders, natch, charfpp if you don't, bitmap fpp if you want more colours, or some crazy assed fun combination.
step 2: for each possible FPP line (you need as many of these for maximum smoothness) calculate a sinus line for finalY=yval for this line. You can do this each frame, or once and just move the y sinus.
step 3: calculate each y line in your raster IRQ, and set the FPP display list appropraitely from a table based on the y output.
step 4: display fpp according to display table.
maybe i'll upload one appropriatly commented and commentated to codebase later this week, if people are interested in such things.
sad panda, what do you mean with bitmap fpp, i understand sprite fpp and char fpp but never heard of bitmap fpp...
i am just curious.....
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HCL
Registered: Feb 2003
Posts: 728 |
You can do bitmap-fpp just like char-fpp, at least the 20-cycle timing will allow fpp-behaviour. |
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Testa
Account closed
Registered: Oct 2004
Posts: 197 |
Hcl: Nice i didn't know ,do you know a demo with this effect ?or do you mean the already mentioned plasma fpp?.
and what about fli fpp?.. works fli fpp the same as bitmap fpp? or am i totally wrong once again.....
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QuasaR
Registered: Dec 2001
Posts: 145 |
Quote: No, but a sprite-zoomer.
But I think, Graham was first with this kind of zoomer, presented in Parts. |
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HCL
Registered: Feb 2003
Posts: 728 |
Quote: But I think, Graham was first with this kind of zoomer, presented in Parts.
That's a char-based zoomer. But yes, that's his invention.
Oh, and bitmap-fpp.. Yes you get some FLI-like stuff there. |
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WVL
Registered: Mar 2002
Posts: 902 |
Quote: That's a char-based zoomer. But yes, that's his invention.
Oh, and bitmap-fpp.. Yes you get some FLI-like stuff there.
I'm not sure I invented the all-border sprite zoomer.. there might have been some before. The first that comes to mind is the one by Glasnost in The Unnamed Demo ofcourse :) even when that one is a rather different technique (only a few pixels high..)
Might be interesting to tell you the difference between the zoomers in Design Overdose, Comajob and Pearls for Pigs.
Design Overdose and comajobs are basically the same, they're based on a stretched sprite routine, with $d018 switches to get extra lines. For every 21 pixels in the sprite, there are 3 d018 options, to give a 63 pixel high picture (so if you stretch the sprite 3x, you can display the picture at 1x zoom). If you dont stretch the sprite, you're at minimum height, at 1/3 zoom.
I think this 'shrinking' trick was invented by Pernod btw ;) just to give some credits ;)
The difference between the comajob one and the one is design overdose is that graham worked hard to make it more flexible, especially by rearranging the sprites when it moves into the borders..
The one in Pearls for Pigs is different. It uses sprite-fpp to shrink and expand in y, basically this allows you to shrink down to 1 single pixel, or to display the picture upside-down. You can also move the picture completely in the upper border (meaning it's possible to only show the bottom pixelrow at the complete top of the screen). With the $d018 technique, you can only move the first 2 pixelrows out of the topborder.. Basically this one is a lot more flexible :) |
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