Block zoom effect

[Wrathchild]

Thought I'd throw a new topic out there...

 

I bought a SNES around the beginning of the year and

a commonly (often over-ly) used effect was to zoom out/in

on an portion of an image such that it ended up using

enormous 'pixels'.

 

Another effect is to blur the image in by gradually defining

the tiles that make up a picture.

 

Have any such effects been attempted in some A8 demos?

(or any 6502 based machine for that matter)

 

If not, how would you approach it... choice of graphics mode etc.

 

Regards,

 

Mark

[Heaven/TQA]

several "snes" effects are used in numen demo...

 

f.e. alpha blending and zooming (well...not really...fractal zoom... )

 

"hardware" zoom can be simulated on atari 8bit computers by using the several build in gfx modes which display the same gfx data but in another resolution... but never tried that way because you just have 1x,2x,4x zoom... but not inbetween... as snes or GBA.

 

a good example for "real" zooming is the oldie but goldie seven cities of gold... when you enter something it zooms correctly "into" it...

and the game uses "streaming" technology from floppy discs which is quite good!!! and a map generator for endless fun...never the same game...

 

hve

[Heaven/TQA]

and a lot of demos (around 1996) have done so called "roto-zoomers" where they rotated and zoomed fast textures or pictures no problem to do that in 50 FPS... even on 6502...because it is simple...

 

check out "asskicker" by shadows or our "ultra" demo where we zoomed textures of an rotating cube...

 

its really simple and it is NOT precaclulated like f.e. trilinear mapping on modern gfx cards... (well... i know that it is not the same...but i mean the precalculating of textures). the whole effect is based on storing the texture in a proper way in memory where the CPU is just "coping" the stuff to screen without nearly any calculation...

 

hve

[Sheddy]

I wondered a few years back why the characters in Doom were so chunky when zoomed in - one possible reason, I figured was because it could be a good way to hold the data - already zoomed.

 

Tried a few routines on the 8-bit and it made it easier to have a byte per pixel for scaling down (rather than up) So you have a maximum of say 4x zoom in the 160 pixel modes.

 

All you do is sample the data pixels every 1+zoom fraction and output them a pixel at a time into a temp zp, then chuck it at the screen when it gets a full byte.

 

If you want to do an exact to pixel size you could use the Bressenham line draw method (keep adding size you want till get to actual size and sampling next pixel, then skip a pixel when you reach that limit)

 

I expect demo coders have a better way of doing things, but this did actually work quite quickly. The hardest bit was centering it up.....

 

Chris