No Fragments Archive 10: Diskmags/nf_archive_10.iso/MAGS/ST_USER/1990/USERSP90.MSA/TEXT_COLOUR.DOC

Text File | 1990-07-25 | 2KB | 36 lines

                   ALL THE COLOURS OF THE RAINBOW


    Colin Faller presents a scrolling multicolour demo in Fast BASIC!


Have you ever seen those demonstration programs that display more than 16
colours on the screen at the same time? They are usually machine code programs
that use horizontal and vertical blank interrrupts, and other hideously complex
technical stuff to display multiple palettes. It's not necessary!

    There is another way to achieve the same effect, and from simple BASIC!
It's actually a trick, or optical illusion because what you do is mix two
colours together by plotting alternate dots in one colour and then going back
and filling in the gaps with the other colour. The two merge onscreen to
produce a different colour. The effect is better with poor quality TVs and
monitors because the coloured are more blurred.

    There are three demonstration programs. COLOUR1.BSC a small program that
appears to display 80 colours on the screen at the same time. COLOUR2.BSC is
more complicated because it scrolls the 80 colours in two directions. You can
scroll the colours quickly or slowly up or down the screen. To scroll the
colours in the opposite direction press the Alternate key.

    To change the speed you should press the Control key - this toggles between
a fast and slow scroll. To change the pattern press the left Shift key, once
you reach pattern seven you will start back at the beginning again. COLOUR3.BSC
not only scrolls up and down at the same time, but also scrolls from left to
right and right to left.


HARDWARE: ALL STs, COLOUR ONLY (ALSO REQUIRES FAST BASIC)