Shapes and lines

There are six shapes, and each asks for its own numbers: a corner here, a centre there, a radius elsewhere

easyYou need: The first picture

steptick 0

Draw0

clear

rgb

Draw1

color

rgb

a

Draw2

rect

xy

widthheight

Draw3

line rect

xy

widthheight

Draw4

stroke

Draw5

line

xy

x2y2

Draw6

color

rgb

a

Draw7

poly

xy

sidesradius

rotation

Draw8

line poly

xy

sidesradius

rotation

Draw9

triangle

xy

x2y2

x3y3

Draw Flush10

Stop11

@counter0number

Everything the display can do is drawn here: a fill and an outline, a line, a hexagon, a triangle in outline and a triangle filled.

What each shape asks for

Command	Fields	What it counts from
rect	x y width height	the bottom left corner
lineRect	x y width height	the same, but in outline
line	x1 y1 x2 y2	point to point
poly	x y sides radius rotation	from the centre
linePoly	x y sides radius rotation	the same, in outline
triangle	x1 y1 x2 y2 x3 y3	three vertices

That difference in what a shape counts from is the most common cause of “it drew in the wrong place”. For a rectangle it is a corner, for a polygon the centre.

Note

There is no circle among the commands: you draw one as a polygon with many sides. No more than 25 of them, though — anything above that the display silently trims to twenty-five. That is the limit of smoothness: on 176 dots, twenty-five sides are indistinguishable from a circle.

Line thickness

draw stroke 4

stroke sets the thickness of everything drawn in outline: line, lineRect, linePoly. Like the colour, it holds until the next stroke, and it does not affect fills at all.

Note

Thickness is counted in the same picture dots as the coordinates — not in screen pixels. An ordinary display has 80 per side, a large one 176, so the same numbers on a large display give a smaller-looking shape: it takes up a smaller share of the screen.

Rotating a polygon

The fifth field of poly is an angle in degrees, and it is counted as everywhere in mlog: counter-clockwise, with zero pointing right.

draw poly 88 88 3 40 0
draw poly 88 88 3 40 180

Two triangles from the same point, rotated relative to each other — a star. Half the pictures on displays are built on that.

Remember

• rect and lineRect count from a corner, poly and linePoly from the centre.
• A circle is drawn as a polygon; there can be at most 25 sides, the extra are trimmed silently.
• stroke sets outline thickness and holds, like the colour.
• Rotation is given in degrees, counter-clockwise.

Task

Change draw poly 45 40 6 30 0 in the example to draw poly 45 40 25 30 0 and run it: the hexagon becomes a circle. Put 40 and the picture does not change at all — a display does not draw more than 25 sides.

Then set draw stroke 1 and look at the line: it becomes a hair. And with draw stroke 20 the line covers a third of the display — thickness grows both ways from its middle.