RELATIVE MODE
Pair of coordinates such as:
across, up
normally define a point relative to the origin 0,0 in the bottom left hand corner of a window (or
elsewhere if you choose). It is sometimes more convenient to define points relative to the current
cursor position. For example the square above may be plotted in another way using the LINE_R
statement which means:
"Make all pairs of coordinates relative to the current cursor position."
POINT 60,50
LINE_R 0,0 TO 10,0 TO 0,10 TO -10,0 TO 0,-10
First the point 60,50 becomes the origin, then, as lines are drawn, the end of a line becomes the
origin for the next one.
The following program will plot a pattern of randomly placed coloured squares.
100 REMark Coloured Squares
110 PAPER 7 : CLS
120 FOR sq = 1 TO 100
130 INK RND(1 TO 6)
140 POINT RND(90),RND(90)
150 LINE R 0,0 TO 10,0 TO 0,10 TO -10,0 TO 0,-10
160 END FOR sq
The same result could be achieved entirely with absolute graphics but it would require a little more
effort.
CIRCLES AND ELLIPSES
If you want to draw a circle you need to specify:
position say 50,50
radius say 40
The statement
CIRCLE 50,50,40
will draw a circle with the centre at position 50,50 and radius (or height) 40 units, see figure:
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