cycled to produce the final rainbow pattern, and their format comprises three values contained in each relevant pair of brackets, as follows:
(number,step,count)
Number refers to the number of scan lines assigned to one colour value. Think of it as controlling the "speed" of the sequence. Step is a value to be added to the colour, which controls the colour change. Count is simply the number of times this whole process is performed.
RAINBOW
instruction: display a rainbow
Rainbow number,offset,vertical position,height
The last example also demonstrates the parameters of the RAINBOW command, which is used to display one of the rainbows created with SET RAINBOW.
The rainbow number is obvious, and refers to one of the four possible rainbow patterns from 0 to 3. The offset sets the value for the first colour in the table created with SET RAINBOW, and it governs the cycling or repetition of the rainbow on screen.
The vertical position is a coordinate which must have a minimum value of 40, and it affects the starting point of the rainbow's vertical display on screen. If a lower coordinate is used, the rainbow will be displayed from line number 40 onwards.
Finally, the height number sets the rainbow's vertical height in screen scan lines.
Please note that normally only one rainbow at a time can be displayed at a particular scan line, and the one with the lowest identification number will be drawn in front of any others However, experienced Amiga users will be able to start more than one rainbow at the same line, using the Copper. See Appendix F for an explanation of this technique.
RAINBOW DEL
instruction: delete a rainbow
Rainbow Del
Rainbow Del number
Use this command on its own to get rid of all rainbows that have been set up. If a rainbow identity number is added, then only that particular rainbow will be deleted.
RAIN
function: change the colour of a rainbow line
Rain(number,line)=colour
This powerful rainbow instruction allows you to change the colour of any rainbow line to value you choose. RAIN is followed by a pair of brackets containing the number of the rainbow to be changed and the scan line number that is to be affected.