coopercorona / shape-repo Goto Github PK

Variety of classes defining different shapes used for collision detection.


### CSShape

Don’t use CSShape directly; it is abstract.

If you wish to make a subclass of CSShape, you must override these methods:
	-[transpose:]
which takes a CGPoint as an argument and moves
the shape according to the x and y values of the point
	-[pointLiesInside:]
which returns a boolean that states whether
a given point lies inside (or on) the shape.
(OPTIONAL)	-[getRandomPoint]
which returns a random point inside/on the shape


### CSShapeGroup

CSShapeGroup contains an array of shapes that can be
tested against other shape groups. For example, you
could define a group comprised of two separate circles,
and if either of them trigger a collision, the shape
group will detect it.
	
Change the ‘center’ property to move the shape group.
However, shape groups initially start at point {0, 0}.
All shapes are therefore anchored as they were before
being in a shape group. So setting a group’s center to
{20, 20} will change a circle initially centered at
{10, 10} will then be centered at {30, 30}.


### CSPoint

CSPoint defines a point in space. CSPoints only
collide with other shapes if the point lies inside
the shape (or in the case of a point, they must
occupy the same point).


### CSLineSegment

CSLineSegment defines a line segment. When
instantiating a line segment, pass in the
two endpoints of the line segment.


### CSRectangle

CSRectangle defines a rectangle.

You can access the line segments that
comprise the rectangle with -[getLineSegments].


### CSTriangle

CSTriangle defines a triangle.

You can access the line segments that
comprise the triangle with -[getLineSegments].


### CSCircle

CSCircle defines a circle.

	-[getPositiveYforX:]
and
	-[getNegativeYforX:]
return the y-value corresponding to the given
x-value. They return 0 if the x-value is invalid.

	-[getPositiveXForY:]
and
	-[getNegativeXForY:]
return the x-value corresponding to the given
y-value. They return 0 if the y-value is invalid.

	-[getPointForAngle:]
returns the point on the circle
corresponding to the given angle.


### CSEllipse

CSEllipse defines an ellipse (oval).

	-[getPositiveYforX:]
and
	-[getNegativeYforX:]
return the y-value corresponding to the given
x-value. They return 0 if the x-value is invalid.

	-[getPositiveXForY:]
and
	-[getNegativeXForY:]
return the x-value corresponding to the given
y-value. They return 0 if the y-value is invalid.

	-[getPointForAngle:]
returns the point on the ellipse
corresponding to the given angle.

### Note about Ellipses
Collision detection for ellipses are not quite
perfect.

I’ve yet to find a mathematical formula
determining collision detection, so I just test
the far left, middle, and far right of the
overlapping portions of the ellipse (if the far
left of the first ellipse is greater than the
far left of the second ellipse, but vice-versa
for the far right, then they collide, and etc.).

If anyone figures out an exact formula for collision
of two ellipses, then I would gladly update the code
along with proper attribution.