4 ms·

The Greatest Justification For Messed-Up Video Game Graphics

45 points by fogus 15y ago

rbanffy 15y ago
Without an explanation of why they had to make waistlines transparent to enable multi-player mode, it doesn't look very convincing. Couldn't they just move the torsos down or the legs up one pixel? I'm sure the C64 graphics hardware allowed that. On an Apple II, I was, once, asked to move something half a pixel to the left. And I did it. ;-)
- simcop2387 15y ago
  yea I'm not sure why they had to have the gap, but from the manual it looks like they used two halves for making the characters so they could reuse assets more and save a bit on ram to get it all working.
- chris_wot 15y ago
  I'm going to sound very stupid, but how did you do it? :-)
  - rbanffy 15y ago
    On the HGR modes, every 7 pixels of a line were packed into one byte - 40x7 = 280 pixels per line. The 8th bit switched the whole byte half a pixel to the left. This was also used to make different colors - the timing change shifted the pixels in relation to the color cycler, making the colors available in that 7-pixel group different (pink and green for off, blue and orange for on). White was done with two contiguous pixels. I think early IIs didn't have this 8th bit magig, but, from the II+and on, all IIs had it.
    - chris_wot 15y ago
      Wow! I've heard of some neat performance hacks, but that's pretty cool - the only one better was the hack that was done to get rectangles with circular corners on the Mac.
- mrcharles 15y ago
  I would guess it was scan-line related, and that the context switch to allow for the bottom half of the bodies took longer than the h-blank required to render that waist line. (Random guesstimation).
antidaily 15y ago
It was either that or remove Abobo's mustache. Clear choice.
Flow 15y ago
As an old C64 hacker that implemented several sprite multiplexers I can write more about the difficulties they had. First, the characters used one multicolored sprite(which gives you double-width pixels), and on top of that sprite they put a black-bordered monochrome(single-pixel widths) sprite to give the characters a cartoony feel. Maybe the memory savings was from reusing frames from one of these sprites, I don't know. All the above is for above the waist. Then, when the raster has painted the last line of those sprites, an IRQ occurs and the sprites are moved 21 pixels down and have different frames and perhaps even new colors assigned to them. This is where the difficulties happen. You have to update 8 sprite y-positions and 8 sprite frame indices. Also up to 4 colors if that is also changed. You only have one scanline(63 cycles) to do this and one update is LDA + STA = 2 + 4 = 6 cycles. So 8+8+4 moves is 20*6 cycles = 120 cycles. Just less than 2 scanlines. They could have solves this by spreading out the sprites a bit in the y-direction so they had to do less but one more scanlines. I don't think anyone would even see this. Most sprite multiplexers sorted the sprites by y-position and then did one IRQ per sprite. If you did this you'd do much less each time and if you could spare the IRQ overhead you'd easily could have 32 sprites on-screen.
- rbanffy 15y ago
  Wow! That's an amazing description! It didn't occur to me they were reusing the sprites. In any case, it shouldn't be that hard just to draw a bunch of black pixels on the waistline before the beam reaches the waistline and erase the line if a player moves.
- jaylevitt 15y ago
  That's also why Q-Link had the signature "squiggly menus" that acted as the AJAX spinner of the day... it drew the menus by changing the background color at a certain raster line, and the Commodore's serial routines (completely implemented in software) had to disable interrupts while they sent or received data. I seem to recall Ray Kelm worked around this for the CNet/Image BBS sysop console in his custom high-speed serial routines, but I may be conflating stories. (Commodore's serial routines couldn't go far above 2400bps; Ray managed to get 9600 working reliably.)
bitwize 15y ago
Man I wish Capcom had traded glitchy graphics for the ability to swap characters in in PlayStation X-Men vs. Street Fighter...

45 points by fogus 15y ago

Without an explanation of why they had to make waistlines transparent to enable multi-player mode, it doesn't look very convincing. Couldn't they just move the torsos down or the legs up one pixel? I'm sure the C64 graphics hardware allowed that. On an Apple II, I was, once, asked to move something half a pixel to the left. And I did it. ;-)

simcop2387 15y ago
yea I'm not sure why they had to have the gap, but from the manual it looks like they used two halves for making the characters so they could reuse assets more and save a bit on ram to get it all working.
chris_wot 15y ago
I'm going to sound very stupid, but how did you do it? :-)
- rbanffy 15y ago
  On the HGR modes, every 7 pixels of a line were packed into one byte - 40x7 = 280 pixels per line. The 8th bit switched the whole byte half a pixel to the left. This was also used to make different colors - the timing change shifted the pixels in relation to the color cycler, making the colors available in that 7-pixel group different (pink and green for off, blue and orange for on). White was done with two contiguous pixels. I think early IIs didn't have this 8th bit magig, but, from the II+and on, all IIs had it.
  - chris_wot 15y ago
    Wow! I've heard of some neat performance hacks, but that's pretty cool - the only one better was the hack that was done to get rectangles with circular corners on the Mac.
mrcharles 15y ago
I would guess it was scan-line related, and that the context switch to allow for the bottom half of the bodies took longer than the h-blank required to render that waist line. (Random guesstimation).

antidaily 15y ago

It was either that or remove Abobo's mustache. Clear choice.

Flow 15y ago

As an old C64 hacker that implemented several sprite multiplexers I can write more about the difficulties they had. First, the characters used one multicolored sprite(which gives you double-width pixels), and on top of that sprite they put a black-bordered monochrome(single-pixel widths) sprite to give the characters a cartoony feel. Maybe the memory savings was from reusing frames from one of these sprites, I don't know. All the above is for above the waist. Then, when the raster has painted the last line of those sprites, an IRQ occurs and the sprites are moved 21 pixels down and have different frames and perhaps even new colors assigned to them. This is where the difficulties happen. You have to update 8 sprite y-positions and 8 sprite frame indices. Also up to 4 colors if that is also changed. You only have one scanline(63 cycles) to do this and one update is LDA + STA = 2 + 4 = 6 cycles. So 8+8+4 moves is 20*6 cycles = 120 cycles. Just less than 2 scanlines. They could have solves this by spreading out the sprites a bit in the y-direction so they had to do less but one more scanlines. I don't think anyone would even see this. Most sprite multiplexers sorted the sprites by y-position and then did one IRQ per sprite. If you did this you'd do much less each time and if you could spare the IRQ overhead you'd easily could have 32 sprites on-screen.

rbanffy 15y ago
Wow! That's an amazing description! It didn't occur to me they were reusing the sprites. In any case, it shouldn't be that hard just to draw a bunch of black pixels on the waistline before the beam reaches the waistline and erase the line if a player moves.
jaylevitt 15y ago
That's also why Q-Link had the signature "squiggly menus" that acted as the AJAX spinner of the day... it drew the menus by changing the background color at a certain raster line, and the Commodore's serial routines (completely implemented in software) had to disable interrupts while they sent or received data. I seem to recall Ray Kelm worked around this for the CNet/Image BBS sysop console in his custom high-speed serial routines, but I may be conflating stories. (Commodore's serial routines couldn't go far above 2400bps; Ray managed to get 9600 working reliably.)

bitwize 15y ago

Man I wish Capcom had traded glitchy graphics for the ability to swap characters in in PlayStation X-Men vs. Street Fighter...