Pivot Point

[whitetiger0990]

How would i ahev line 'A' pivot on point 'B' to touch semicircle 'C'?

[Diroga]

for loop use cirlce with radians. or draw part of a circle with cos and sin

[whitetiger0990]

for loop use cirlce with radians. or draw part of a circle with cos and sin

huh?

[toonski84]

Code:

pi! = atn(1) * 4
cx! = 160 ' Center X
cy! = 100 ' Center Y
r! = 20 ' Radius
angle! = 180
theta! = angle! * pi! / 180

LINE (cx, cy)-(cos(theta!) * r! + cx!, sin(theta!) * r! + cy!)

in general:

when you have a radian (angle from 0 to the circumferance of a unit circle, a unit circle having a radius of one, 2 * pi), a cosine (cos) returns the x length of a line in that direction with a lenght of 1. the sine (sin) returns the y height of that line. So if you multiply that figure by the radius, you will get the x and y components for a line of r length (r being the radius).

oh yeah, and for pivoting, just thange angle!, which goes from 0 to 359 (starting from the right and going counter clockwise). Making this value higher will make the line move counter clockwise.

[whitetiger0990]

thanks

[Diroga]

if you dint get that this may help

Code:

SCREEN 13
CONST rad = (3.141592654# / 180)
FOR i = 0 TO 360
x = (COS(i * rad) * 10) + 100
y = (SIN(i * rad) * 10) + 100
LINE (100, 100)-(x, y), 15
NEXT

[Neo]

That example will draw a large amount of lines from (100,100) to a point on the circle.

Let's see:

Code:

'$DYNAMIC
DEFINT A-Z

SCREEN 13

' this draws:
'- Line B
'- Semicircle C
' r^2=x^2 + y^2
' r=50
' y = SQR(r^2-x^2)
oldY = 0
height = 0
FOR x = -50 TO 50
   y = -INT(SQR(r^2-x^2))
   IF x = 0 THEN height = y
   IF x > -50 THEN LINE (x - 1 + 160, oldY + 100) - (x + 160, y + 100), 1
   oldY = y
NEXT x
LINE (110,100)-(210,100), 2

' this draws:
'- Line A pivot on Line B and touching C
LINE (160,100)-(160,100+height), 3

Done by heart, hope there aren't any bugs in it. And I hope you can do something with it!