One of many things missing in CPC Demos is...

[tastefulmrship]

Now that our demo coders have stopped creating logo/raster/scroller one-screen intros and started to expand their repertoires and the limits of the CPC, there are a load of C64, Amiga and PC routines that have not been seen on CPC, and I was wondering if some of them were even possible on CPC.
My first question is; are 3D (or 2D) SHADE CLUSTERS possible on our machine?

Now, I have been spending ages trying to remember which Amiga demos had clusters and I can't find any of them...
So, instead I've done a quick BASIC PLOT routine to show you the sorta thing I mean.

Code Select Expand


10 RANDOMIZE TIME
20 MODE 1
30 BORDER 1:INK 0,1
40 INK 1,26:INK 2,15:INK 3,3
50 :
60 x%=320:y%=200:a%=0
70 :
80 PLOT x%,y%,a%
90 a%=INT(RND*4)+1
100 IF a%=1 THEN x%=x%-2:IF x%<0 THEN x%=0
110 IF a%=2 THEN y%=y%-2:IF y%<0 THEN y%=0
120 IF a%=3 THEN x%=x%+2:IF x%>638 THEN x%=638
130 IF a%=4 THEN y%=y%+2:IF y%>398 THEN y%=398
140 GOTO 80


I had forgotten about NEXUS7 by ANDROMEDA! (Shade cluster starts at 02:24)

Andromeda - Nexus 7 (1994) Amiga - YouTube

[TFM]

Odiesoft did some stuff like 3D and Shading etc...
I did too, but for my OS, so nobody ever saw it ,-)

[arnoldemu]

Now that our demo coders have stopped creating logo/raster/scroller one-screen intros and started to expand their repertoires and the limits of the CPC, there are a load of C64, Amiga and PC routines that have not been seen on CPC, and I was wondering if some of them were even possible on CPC.
My first question is; are 3D (or 2D) SHADE CLUSTERS possible on our machine?

Now, I have been spending ages trying to remember which Amiga demos had clusters and I can't find any of them...
So, instead I've done a quick BASIC PLOT routine to show you the sorta thing I mean.

Code Select Expand


10 RANDOMIZE TIME
20 MODE 1
30 BORDER 1:INK 0,1
40 INK 1,26:INK 2,15:INK 3,3
50 :
60 x%=320:y%=200:a%=0
70 :
80 PLOT x%,y%,a%
90 a%=INT(RND*4)+1
100 IF a%=1 THEN x%=x%-2:IF x%<0 THEN x%=0
110 IF a%=2 THEN y%=y%-2:IF y%<0 THEN y%=0
120 IF a%=3 THEN x%=x%+2:IF x%>638 THEN x%=638
130 IF a%=4 THEN y%=y%+2:IF y%>398 THEN y%=398
140 GOTO 80


I had forgotten about NEXUS7 by ANDROMEDA! (Shade cluster starts at 02:24)

Andromeda - Nexus 7 (1994) Amiga - YouTube

interesting. I haven't seen this before on cpc.
I would say it's definitely possible. It's sprites moving in a 3d motion, with some precalculated sprites at different zoom levels.
Plot them with OR, limit them to 4 colours, and use another set of 4 colours for background and it could work quite fast.
alternatively, you'd have to sort them in z potentially, then mask them on using a custom function.

either way, it's possible I recon.

[Gryzor]

So, what *is* a shade cluster? To me it looks like semi-randomly drawn particles and clouds...?

[db6128]

Plot them with OR, limit them to 4 colours, and use another set of 4 colours for background and it could work quite fast.

Ah yeah, this is the Rotovision/Mission Genocide (a.k.a. ZTB) method. I read about this not long ago and was impressed by its logic, even despite the limitations it imposes. Was this method actually used in many other games/contexts?

As for demos, I've been working my way through various ones in the GoodCPC set. Probably the most impressive things I've seen so far have been by OdieSoft, specifically the rotating textured cube with shading, and the rotating tower with a frog walking around it. There was another demo that had about four split-screens with some really impressive types of effects and scrollers that I'd never seen before (yes, wow, even scrollers can be made interesting with enough skill ), but I don't remember its title or creator(s).

A lot of the things that can be done are very impressive. Has anyone ever done much to incorporate demo-esque effects into games, or do they consume so much CPU and RAM that they can't coexist with the more complex logic that would be required by an engine? Excuse the nooby question; I still have a lot of DSKs to get through.

[arnoldemu]

Ah yeah, this is the Rotovision/Mission Genocide (a.k.a. ZTB) method. I read about this not long ago and was impressed by its logic, even despite the limitations it imposes. Was this method actually used in many other games/contexts?

Yes a few did. Ghosts and Goblins, LED Storm, Ghouls n Ghosts.

As for demos, I've been working my way through various ones in the GoodCPC set. Probably the most impressive things I've seen so far have been by OdieSoft, specifically the rotating textured cube with shading, and the rotating tower with a frog walking around it. There was another demo that had about four split-screens with some really impressive types of effects and scrollers that I'd never seen before (yes, wow, even scrollers can be made interesting with enough skill ), but I don't remember its title or creator(s).

A lot of the things that can be done are very impressive. Has anyone ever done much to incorporate demo-esque effects into games, or do they consume so much CPU and RAM that they can't coexist with the more complex logic that would be required by an engine? Excuse the nooby question; I still have a lot of DSKs to get through.

Generally the demo effects are specific to the demo, and often use all cpu time. Normally they can't be used within a game.

These effects have been used in games:
- rasters
- rupture/split-screen
- hardware scrolling
- sample playback
- scrollers.

[Optimus]

Wow, one of my favorite rarely seen effects! So rare that I can hardly even remember any other demos (modern or not) remaking this effect even if it's not hard.


It's basically a 3d random walker, then points projected on 2d screen, and blended bobs added together or something like that (maybe a simple xor will suffice).
Most intensive parts would be 3d rotations and projection and then of course the rendering. The rendering is always my favorite, I think maybe 200 would be needed to look enough blobs on screen (in my tiny intros with blobs I had 64 blobs and more could be written, bottleneck being the chunky tile renderer and not individual blobs, and they were too big even for this effect), I think it's doable. 3d math scare me more, but I have a precalc idea since all the points positions in the cube for random walk are few and could be precalced. I think it's quite probable on amstrad and frame rate wouldn't suffer much with some tricks.


There are more effects I would like to see (and do if someone else is not the first) on CPC. Polygons. Not just flat but gouraud shading. I love it!!! Have seen 2-3 very good ones on C64 and 10s of more ugly ones. Maybe more (glenz, texture mapping, etc). The past month I have been coding a triangle/polygon rasterizer for CPC based on a much easier algorithm that the complex triangle rasterizers you will read on tuturials for PC. It's going very well and will be pleased to use this in it's various stages as it evolve for incoming demos.


Then some more rare effects I haven't seen. Bouncing sphere mapping (like on second reality). I was thinking the 2bit palete trick I recently understood would be great to make the sphere mapping also blend nicely with background. Might use the palete trick in some effect ideas I have too. Other effect, polar swirl but on textured image (like here minute 1:15). I have done polar effects with simple plasma colors (where angle and radius affect color gradient) but thinking about proper mapping that doesn't look ugly to affect 2d cartesian bitmap needs a bit more thought from my side. I would like to see this too on CPC.


I believe there are more to see on demos. I just can't refresh my mind right now.

[TFM]

Oh, IIRC the Bollawares did some stuff like this too.

[Devilmarkus]

Tasty's code inspired me:

Code Select Expand

10 RANDOMIZE TIME
20 MODE 1
30 LOCATE 1,1:PRINT CHR$(23);CHR$(1)
40 BORDER 1:INK 0,1
50 INK 1,26:INK 2,15:INK 3,3
60 :
70 x%=320:y%=200:a%=0:INPUT"Factor:",p%:CLS:xa%=320:ya%=200:IF p%<1 THEN p%=1
80 PLOT 320,200,0
90 :
100 MOVE xa%,ya%:DRAW x%,y%,1:IF TEST(x%,y%) = 0 THEN PLOT x%,y%
110 MOVE 640-xa%,400-ya%:DRAW 640-x%,400-y%:IF TEST(640-x%,400-y%) = 0 THEN PLOT 640-x%,400-y%
120 MOVE xa%,400-ya%:DRAW x%,400-y%:IF TEST(x%,400-y%) = 0 THEN PLOT x%,400-y%
130 MOVE 640-xa%,ya%:DRAW 640-x%,y%:IF TEST(640-x%,y%) = 0 THEN PLOT 640-x%,y%
140 xa%=x%:ya%=y%
150 a%=INT(RND*4)+1
160 IF a%=1 THEN x%=x%-p%:IF x%<0 THEN x%=x%+p%
170 IF a%=2 THEN y%=y%-p%:IF y%<0 THEN y%=y%+p%
180 IF a%=3 THEN x%=x%+p%:IF x%>638 THEN x%=x%-p%
190 IF a%=4 THEN y%=y%+p%:IF y%>398 THEN y%=y%-p%
200 GOTO 100


Factor is the step between pixels. Should be around 4-40

[AMSDOS]

Tasty's code inspired me:
Factor is the step between pixels. Should be around 4-40

Having the Factor set to 4 just blew me away. 

[Gryzor]

This looked nice. Even for very large numbers it looks like a vector game.