Search site Dead Hackers Society
Other BBSes »

Silly Venture 2019

Sommarhack 2019
Demoscene   º   Coding   º   CT60   º   Buy/sell   º   Misc/crap   º   Alive magazine   º   SNDH/Tracking

Atari coding BBS
Re: Overscan+rasters
Posted by: ggn May,03.2017-08:20 

(Just to get the ball rolling until the people that wrote these formats step forward and explain better)

First of all, when you say "rasters" do you mean a single palette change per scanline or multiple (like MPP or PCS does)?

The first is really simple: you get 16 unique colours per line, so you can plan your image to work with this.

The second is a more complex subject: yes you do get more than 16 colours per scanline but there is a big limitation: you cannot have a stable amount of colours throughout the line.

To get technical for a moment, it has to do with the CPU being unable to reload all palette colours instantly. Which means that you might get palette index 3 (for example) quite early at the left side of the line, reusing it with another colour will take a fixed amount of time (which depends on the format you use).

So what this boils down to is: you can use a single colour inside a fixed window. So for index 1 this will be (again, this is an example - actual figures will vary depending on the format you use) pixels 16 to 80, index 2 pixels 32 to 96, index 3 pixels 64 to 112. So think of it as a sliding window.

Of course you probably don't have much control over this since you will probably use a converter to this format that does all the colour scheduling automatically for you. But I think that if you follow the above rule of thumb you can make its life much easier.

Finally if you want to see this in action try painting a bit with spectrum 512 and watch it as it reschedules palettes and stuff in real time as you lay down many cols per line - plus it's not a bad drawing program really :D.

Hope this helps, any multi palette format author is free to chip in this thread and completely shoot the above down if I'm wrong :).

[All messages in this thread]

Topic Posted by  Date 
Overscan+rasters mic/dune May,02.2017-12:38
  Re: Overscan+rasters leonard May,02.2017-14:29
    Re: Overscan+rasters mic/dune May,02.2017-23:39
      Re: Overscan+rasters ggn May,03.2017-08:20
        Re: Overscan+rasters dml May,03.2017-12:22
          Re: Overscan+rasters Troed May,26.2017-07:48
      Re: Overscan+rasters mic/dune May,03.2017-18:25
        Re: Overscan+rasters leonard May,03.2017-22:49
          Re: Overscan+rasters mic/dune May,04.2017-07:44
          Re: Overscan+rasters evil May,05.2017-20:26
            Re: Overscan+rasters mic/dune May,05.2017-22:54

Message board and comments are now read-only

Due to abuse of the message boards we have put the entire site in read-only mode. That means you can't post new threads or reply to old messages and you can't add comments in VideoDB and PicDB.

Some messages have been erased from reading, but are stored in case they need to surface again.

After 17 years and 45000 messages we're shutting down due to one person.

© 1994-2019 Dead Hackers Society Contact: Anders Eriksson