koobas.hobune.stream
Screen point to point on Plane WITHOUT Raycast?
How do I use the position taken from Input.mousePosition, take a gameobject (which is a plane), and calculate the local space point on the plane (or world point on the plane doesn't matter)? I can see why raycast would be useful with multiple gameobjects, but I only have one and I'm sure there is another way without using it, whether it be built in or an algorithm. Thanks for your help.
The trickiest part is converting a 2d point on the screen into a 3d direction. Luckily, Unity is kind enough to provide you a nifty algorithm to do this: Camera.ScreenPointToRay which will give you a Ray, essentially a start point (the camera's position) and a direction. Assuming that your plane is horizontally flat, all you have to do is solve a linear equation.
You can find the delta between the ray's start point's y position and the plane's y position and multiply that by the direction of the ray to find how much the position as changed. Then normalize the direction by its y position and... Okay, this is getting kind of confusing to. Here's an example:
Plane plane = new Plane();
Camera camera = new Camera();
void Start()
{
plane.transform.position = Vector3.zero;
camera.transform.position = Vector3.up * 15;
}
void Update()
{
if (Input.GetMouseButtonDown(0))
{
Nuke (GetIntersectionPos (plane, camera));
}
}
Vector3 GetPlaneIntersection(Plane plane, Camera camera)
{
Ray ray = camera.ScreenPointToRay(Input.MousePosition);
float delta = ray.origin.y - plane.transform.position.y;
Vector3 dirNorm = ray.direction / ray.direction.y;
Vector3 IntersectionPos = ray.origin - dirNorm * delta;
return IntersectionPos;
}
Awesome! Could you tell me where the concept came from? I want to formalize the knowledge..
Again, thank you for the very good answer, it was hard to find it.
About the concept, could you be more specific? I am putting debug draw lines so I can understand what really is going on, but not getting it yet.
This is the main confusion for me. Vector3 dirNorm = ray.direction / ray.direction.y;
