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Forums > C64 Coding > 'HCL-plasma' - how does it work?

2008-11-02 23:16

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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2008-11-03 22:12

HCL

Registered: Feb 2003
Posts: 727

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.

2008-11-04 09:13

WVL

Registered: Mar 2002
Posts: 889

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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