| |
Joodas
Registered: Oct 2011
Posts: 8 |
Joe's 136 colors technique
Hi all,
I am looking for information about Joe's 136 colors technique. Any links will be appreciated.
Thank you for help |
|
... 38 posts hidden. Click here to view all posts....
|
| |
Graham
Account closed
Registered: Dec 2002
Posts: 990 |
The vertical green/red bars effect only happens when using composite. If you use S-Video, that effect will not happen.
It's caused when the composite signal is seperated into a luma and a chroma signal again by using a low/high-pass filter with a cutoff frequency ~4 MHz. Since the filter doesn't work perfect, parts of the hires luma pixel pattern will still leak over to the chroma signal.
~8 MHz pixel clock with alternating pixels = ~4 MHz frequency. Remember: Chroma color carrier has 4.43 MHz.
The reason why the pattern is fixed to character sizes is simple. Both, pixel clock and color carrier clock derive from the same master clock: 17.734475 MHz. Divided by 4 it's exactly the PAL color carrier frequency of 4.43361875 MHz, divided by 18 it's the C64 system clock of 0.985 MHz. C64 system clock * 8 is the VIC2 pixel clock of 7.882 MHz. So there is an integer ratio between color carrier and pixel clock of 16/9. :) |
| |
Monte Carlos
Registered: Jun 2004
Posts: 350 |
I give it the name "Geos Pattern" |
| |
Wile Coyote
Registered: Mar 2004
Posts: 635 |
Quote: Here's a photo of a TV with a C64 connected, demonstrating the difference between odd/even mixing:
Rows 1 and 4 contain the plain colours. Row 2 is mixed with colours from row 1 on even lines and colours from row 4 on odd lines. Row 3 is mixed with colours from row 1 on odd lines and colours from row 4 on even lines.
It has been known for a long time, the method of placing one multi colour pixel above another multi colour pixel to produce a new colour. Green and Pink being one of the best combos to produce Beige.
(maybe someone already has) It would be interesting to see a converter that produces an image based on the 28 colours, and outputs and image (using FLI) with pixels that are 2x2 hires pixels / 1x2 multi colour pixels. |
| |
Graham
Account closed
Registered: Dec 2002
Posts: 990 |
To my knowledge used the first time in 46 Colour Demo/Radwar. Another early demo using that effect is Goatbeard/Oneway (12 sprites part). |
| |
ChristopherJam
Registered: Aug 2004
Posts: 1370 |
Redcrab - it's worse than that. Power cycle your c64 and display the same pattern, and there's a good chance the situation will be reversed, (possibly even scrolled by a partial character width? I can't remember now).
It's all to do with the relative phase of the colour signal and the dot clock, and the circuit that produces them doesn't appear to be consistently initialised :( |
| |
Monte Carlos
Registered: Jun 2004
Posts: 350 |
I like that color scheme very much, although it is not complete, as the colors 5,10,12 and 14 can be mixed in any combination. If this would be taken account for, it would be a perfect color scheme.
The disadvantage of this technique is, that it must be calibrated, because some TVs displays mix color 1 when mixing abababab and mix color 2 when mixing babababa and other TVs display the exchanged mix colors.
Also, as seen in "Courtesy of soviet", y soft scrolling causes the mix colors to alternate dependent on the y shift.
If y shift is changed continously, the mix colors flicker.
|
| |
algorithm
Registered: May 2002
Posts: 702 |
Quote: It has been known for a long time, the method of placing one multi colour pixel above another multi colour pixel to produce a new colour. Green and Pink being one of the best combos to produce Beige.
(maybe someone already has) It would be interesting to see a converter that produces an image based on the 28 colours, and outputs and image (using FLI) with pixels that are 2x2 hires pixels / 1x2 multi colour pixels.
Its also less straightforward than that, as the next line color is determined by the previous line color, moving onto the other 2x2 will result in the first line in the next 2x2 section etc, having a different color based on the color on the previous line. Have a look at the Algotecher demo for some examples in MUCSU-FLI (non interlaced) and MR-FLI (interlaced) which utilises the pal blending to create additional colors. Some additional examples in the MUCSU-FLI mode are in the demo 'introducing MUCSU-FLI'
Furthermore, there is the blending that occurs on the horizontal plane as well. Taking these all to account would require a huge lot of computations (unless opting for the suboptimial method)
MonteCarlos, I also believe if the image is scrolled, the issue with the color blends changing can be rectified by scrolling it in even amount eg 2,4,8
ChristopherJam, that is interesting in regards to the initialisation theory, perhaps this may also be linked to the VSP crashes that occur sometimes when powering on the c64.
|
| |
Monte Carlos
Registered: Jun 2004
Posts: 350 |
Yeah, scrolling in even steps doesn't change any color.
I wonder what's that "cool" demo from dez. 1985, radwar cites in their release in the intro?
|
| |
Joe
Registered: Apr 2002
Posts: 224 |
Joodas got an email last saturday, three hours after the opening of this thread. I shared some thoughts on the subject and I can expand a little here:
The actual vista of more colors is of course secondary and more a optimistic will, if one wants, of reading images. I'd rather want to express the possibility of a working method of adding layers on top of each other. Instead of thinking about hatching areas to mold volumes, which is rather the method of an additive color principle (oil or digital means of giving hues, tones and depth): Whereas one thinks of flat representations of objects concerned about ditheringstyle and technique.
I believe that this simple method share similarities to subractive color (water color) where one not only got a grain of texture and new possibilities to handle surfaces as flat fields of information. It might sound silly of introducing color, light, hue and grain (that is scale and dimension) in one and the same mean. We could go on in the mere technical aspect of the dilemma or as I have understood, in a more general form problem. Not very much has happened in the field of c64 art, part from perhaps the graphic-modes and the fact that people are getting better at the craft. Leon and Lars has both showed some very fine ways of dealing with transitional spaces, just as Sit did recently. Carrion showed some potential ways of layering fields and I'm trying to get rid of dithering in the convential manner. Veto showed that fields give rise to complex situations of interdependant narratives and Nada proved the potential of a fine net of sprayed pixels.
We all give rise to different approaches towards representations regardless of the subjective design. That is the most important, I'd guess: To look forward.
As for the Zebras, here's a small demo showing the awkward stripes. |
| |
WVL
Registered: Mar 2002
Posts: 885 |
Instead of scrolling in an even number (2/4/6/whatever) of pixels per frame, you can also scroll in an odd number of pixels, if you have 2 sets of bitmap where you reverse the mixing colors in the 2nd bitmap.
That way the colors stay the same and doesn't depend on the speed that you're scrolling with. -> idea (C) WVL ;) |
| Previous - 1 | 2 | 3 | 4 | 5 - Next |
