Personal Computer News


Keeping Colouring Under Control

 
Published in Personal Computer News #074

Keeping Colouring Under Control

Q. Could you give me any hints about using serial attributes on my Oric 1? I'm trying to produce coloured pie character on the HIRES screen using the FILL command. The problem I have is that after drawing the circle, the control codes for colours appear in black between some of the segments - those which meet in any plane except horizontal. I can't work out why or how to get round the problem.

L. Bancroft
Cambridge

A. The following routine shows how FILL can be used to produce curved areas of colour, without gettiing a black area between them:

 10 HIMEM &97FF (&17FF FOR 16K)
 20 HIRES
 30 CURSET 0,0,0
 40 FOR COLOUR = 1 TO 4
 50 CURSET COLOUR * 30,0,0
 60 FOR F=0 TO 10
 70 CURMOV F,1,0
 80 FILL 1,1,COLOUR+16
 90 NEXT:NEXT
100 GET A$:TEXT:LIST

Understanding how this works may help you sort out your programming problem. Your description isn't very clear, but another difficulty could be caused by drawing the circle. The example program uses background colours only, so try using PAPER or background attribute codes alone (those between 16 and 23): don't put any character codes in the chart.

Yet another reason for the black areas may be that your program is ing incorrect areas, so try PEEKing the screen locations (between 40960 and 49119 decimal) to find out exactly which attribute/character codes are there. Mapping out the screen's contents might be of use because you can see where the problem is. You could then add a few POKEs of character or attribute colours to these relevant screen locations.

L. Bancroft