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Artifact Colors: Difference between revisions
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'''Artifact Colors''' on the CoCo are those extra colors that are formed in specific combinations of dots or lines in the 256x192 two color graphics mode on TV screens and Composite Video monitors. | '''Artifact Colors''' on the CoCo are those extra colors that are formed in specific combinations of dots or lines in the 256x192 two color graphics mode on TV screens and Composite Video monitors. | ||
<!--Due to the limitations of the NTSC signal and the phase relationship between the VDG clock and colorburst frequency, it is not actually possible to display 256 dots across the screen reliably. In the first colorset, where green and black dots are available, alternating columns of green and black are not distinct and appear as a muddy green color. However when one switches to the white and black colorset, instead of a muddy gray as you would expect, you will get either red or blue. Reversing the order of the alternating dots will give the opposite color. In effect this mode becomes a 128x192 4 color graphics mode where black, red, blue, and white are available. Most CoCo games used this mode as the colors available are more useful than the ones provided in the hardware 4 color modes. Unfortunately the VDG internally can power up on either the rising or falling edge of the clock, so the bit patterns that represent red and blue are not predictable. Most CoCo games would start up with a title screen and invited the user to press the reset button until the colors were correct! The CoCo 3 fixed the clock-edge problem so it was always the same (holding F1 during reset would choose the other). On a CoCo 3 with an analog RGB monitor, the black and white dot patterns do not artifact; you'll need to use a TV or composite monitor, or patch the games to use the hardware 128x192 four color mode (where the GIME chip allows the color choices to be mapped). --> | <!--Due to the limitations of the NTSC signal and the phase relationship between the VDG clock and colorburst frequency, it is not actually possible to display 256 dots across the screen reliably. In the first colorset, where green and black dots are available, alternating columns of green and black are not distinct and appear as a muddy green color. However when one switches to the white and black colorset, instead of a muddy gray as you would expect, you will get either red or blue. Reversing the order of the alternating dots will give the opposite color. In effect this mode becomes a 128x192 4 color graphics mode where black, red, blue, and white are available. Most CoCo games used this mode as the colors available are more useful than the ones provided in the hardware 4 color modes. Unfortunately the VDG internally can power up on either the rising or falling edge of the clock, so the bit patterns that represent red and blue are not predictable. Most CoCo games would start up with a title screen and invited the user to press the reset button until the colors were correct! The CoCo 3 fixed the clock-edge problem so it was always the same (holding F1 during reset would choose the other). On a CoCo 3 with an analog RGB monitor, the black and white dot patterns do not artifact; you'll need to use a TV or composite monitor, or patch the games to use the hardware 128x192 four color mode (where the GIME chip allows the color choices to be mapped). --> | ||
=Articles= | |||
{| class="wikitable sortable" | |||
|+ Y=Year, M=Month, P=Page | |||
|- | |||
! Article !! Author !! Product/''Program'' !! Magazine !! Y !! M !! P | |||
|- | |||
| [https://archive.org/details/rainbowmagazine-1988-02/page/n115/mode/2up ''Artifact Colors on CoCo 3's RGB''] || Stephen M. Ostrom || ''Patch'', ''Look'' || ''[[The Rainbow]]'' || style="text-align:center;"|88 || style="text-align:center;"|02 || style="text-align:right;"|114 | |||
|- | |||
|} | |||
=Other Resources= | |||
[https://en.wikipedia.org/wiki/Composite_artifact_colors#TRS-80_Color_Computer Wikipedia Artifact Colors article, CoCo Section] | |||
Latest revision as of 23:38, 4 September 2024
Artifact Colors on the CoCo are those extra colors that are formed in specific combinations of dots or lines in the 256x192 two color graphics mode on TV screens and Composite Video monitors.
Articles
| Article | Author | Product/Program | Magazine | Y | M | P |
|---|---|---|---|---|---|---|
| Artifact Colors on CoCo 3's RGB | Stephen M. Ostrom | Patch, Look | The Rainbow | 88 | 02 | 114 |