B2.World:rayCast
Available since: Gideros 2011.6
Class: b2.World
Description
Ray-casts the world for all fixtures in the path of the ray. Your callback controls whether you get the closest point, any point, or n-points. The ray-cast ignores shapes that contain the starting point.
Listener function is called for each fixture found in the query and accepts 6 parameters (7 if data parameter is provided):
- the fixture hit by the ray
- the x coordinate of the point of initial intersection
- the y coordinate of the point of initial intersection
- the x coordinate of the normal vector at the point of intersection
- the y coordinate of the normal vector at the point of intersection
- fraction
You control how the ray cast proceeds by returning a number:
- return no value or -1: ignore this fixture and continue
- return 0: terminate the ray cast
- return fraction: clip the ray to this point
- return 1: don't clip the ray and continue
<syntaxhighlight lang="lua"> b2.World:rayCast(x1,y1,x2,y2,listener,data) </source>
Parameters
x1: (number) the x coordinate of the ray starting point
y1: (number) the y coordinate of the ray starting point
x2: (number) the x coordinate of the ray ending point
y2: (number) the y coordinate of the ray ending point
listener: (function) the listener function that processes the results
data: (any) an optional data parameter that is passed as a first argument to the listener function optional
Examples
Detecting bodies with raycasting <syntaxhighlight lang="lua"> local raycastCallback function(fixture, hitX, hitY, vectX, vectY, fraction)
--so if this function is called, it means we hit some kind of object --and its fixture is stored in first variable we named "fixture" --so we can for example get body local body = fixture:getBody()
end
--now we add callback function for projected raycast above body --Parameters: --object x coordinate --object y coordinate --projection vector on x axis --projection vector on y axis --callback function local x, y = body:getPosition() world:rayCast(x, y, x, y-100, raycastCallback) </source>
