collision_circle( x1, y1, rad, obj, prec, notme );
| Argument | Description |
|---|---|
| x1 | The x coordinate of the center of the circle to check. |
| y1 | The y coordinate of the center of the circle to check. |
| rad | The radius (distance in pixels from its center to its edge). |
| obj | The object to check for instance collisions. |
| prec | Whether the check is based on pixel-perfect collisions (true = slow) or its bounding box in general (false = fast). |
| notme | Whether the calling instance, if relevant, should be excluded (true) or not (false). |
Returns: Instance id or noone
Collision circle creates a circular zone of the radius given by
the user around the points x1,y1 and then checks that zone for a
collision with any instance of the object specified by the
argument "obj". This check can be either precise or not, but for
precise collisions to be enabled, the object or instance that you
are checking for must also have precise collisions enabled
for their sprite. If not, the default check is based on bounding
boxes. The following image illustrates how this works:
Here, the instance in the middle is using a collision circle to
check for ball objects. Now, the blue ones do not have a
precise bounding box and as you can see, even if the sprite is not
actually touching the circle, the collision can still happen (even
if you set the precise option in the function to true) as the
bounding box of that sprite over-laps the circular area defined by
collision_circle. On the other hand, the green balls will only be
considered in collision if the actual sprite over-laps with the
defined circle. Remember, for precise collisions to be considered
both the object sprite and the collision function must have
precise marked as on. It should also be noted that the return value
of the function can be the id of any one of the instances
considered to be in collision.
if collision_circle(x, y, 20, obj_Cursor, false,
true)
{
image_index = 1;
}
else image_index = 0;
The code above will check a circular are with a 20pixel radius for a collision with "obj_Cursor" and if there is one it will set the image_index of the object running the code to 1, but if there is not it will set the image_index of the object to 0.