Is 320B color flaw present in 320C?

[R_Leo_1]

I've been wondering recently if the bug that is present in the 320B graphics mode (One color of the palette only appearing if it is next to a different color within the same palette) is also present in 320C. I have not been able to utilize 320C graphics in 7800 Basic, so I am unable to test this myself. If anyone has any insight on this that would be awesome, thanks.

[EricBall]

https://atariage.com/forums/topic/272112-sprite-data-to-color-mapping/probably has the info you're looking for, although I don't see the bug you are referring to in 320B - you should be able to have two adjacent sub-pixels with the same color.

[R_Leo_1]

https://atariage.com/forums/topic/272112-sprite-data-to-color-mapping/probably has the info you're looking for, although I don't see the bug you are referring to in 320B - you should be able to have two adjacent sub-pixels with the same color.

 

Thank you, I have used this table you created before. But the bug I'm referring to can be seen here in Rikki & Vikki

 

 

Notice on the water and the rocks that there are vertical bars for one specific color within the palette. This is the bug where if you tried to have the water be solid and not made of vertical bars, the color would just be transparent.

[TailChao]

It's still technically present.

 

This is the bug where if you tried to have the water be solid and not made of vertical bars, the color would just be transparent.

Yeah, specifically it's a quirk of how Write Mode 1 ("x2") works - any value of %xxx00 written to the linebuffer is considered transparent and won't be drawn outside of Kangaroo Mode.

 

320C uses the same Write Mode as 320B (and 160B), but the linebuffer contents are read out differently.

 

Mode   Data              Line Write       Line Read (Output)
---------------------------------------------------------------------
160B : %p + %abcdefgh -> %pefab,%pghcd -> %pefab,%pghcd
320B : %p + %abcdefgh -> %pefab,%pghcd -> %p00ae,%p00bf,%p00cg,%p00dh
320C : %p + %abcdefgh -> %pefab,%pghcd -> %pefa0,%pefb0,%pghc0,%pghd0
                                          ---------------------------
                                          %pppcc,%pppcc,%pppcc,%pppcc

Output %pppcc = Palette ppp (0 - 7) Color cc (0 - 3)

[EricBall]

You're right. In 320B you can't have both of the two half pixels be C1. 320C doesn't have this issue, but it restricts the two half pixels to be either transparent, the same color, or one be the background color.

 

You've also inspired me to revisit my sprite data to color mapping post an make it easier to understand and hopefully use.

 

MARIA.zip

[R_Leo_1]

It's still technically present.

 

Yeah, specifically it's a quirk of how Write Mode 1 ("x2") works - any value of %xxx00 written to the linebuffer is considered transparent and won't be drawn outside of Kangaroo Mode.

 

320C uses the same Write Mode as 320B (and 160B), but the linebuffer contents are read out differently.

 

Mode   Data              Line Write       Line Read (Output)
---------------------------------------------------------------------
160B : %p + %abcdefgh -> %pefab,%pghcd -> %pefab,%pghcd
320B : %p + %abcdefgh -> %pefab,%pghcd -> %p00ae,%p00bf,%p00cg,%p00dh
320C : %p + %abcdefgh -> %pefab,%pghcd -> %pefa0,%pefb0,%pghc0,%pghd0
                                          ---------------------------
                                          %pppcc,%pppcc,%pppcc,%pppcc

Output %pppcc = Palette ppp (0 - 7) Color cc (0 - 3)

 

Awesome! Thanks for the info on this, that'll be extremely helpful for me. Just to clarify though, if Kangaroo mode is turned on, then in 320C I can use 4 solid colors, just no transparency available, right?

 

You're right. In 320B you can't have both of the two half pixels be C1. 320C doesn't have this issue, but it restricts the two half pixels to be either transparent, the same color, or one be the background color.

 

You've also inspired me to revisit my sprite data to color mapping post an make it easier to understand and hopefully use.

 

 

Thanks as well, I'm glad I have inspired you to revisit it! I'll take a look at the updated map

[EricBall]

Awesome! Thanks for the info on this, that'll be extremely helpful for me. Just to clarify though, if Kangaroo mode is turned on, then in 320C I can use 4 solid colors, just no transparency available, right?

 

320C will allow you 4 colors with transparency. However, the two half pixels are either the same color, transparent or one is the background color.

[R_Leo_1]

 

320C will allow you 4 colors with transparency. However, the two half pixels are either the same color, transparent or one is the background color.

 

Thanks for the info Last night I managed to get 320C working in 7800basic so I believe I've got a handle on it now, thanks again!