bool CameraUnProject(Vector3 p, Matrix4x4 cameraToWorld, Matrix4x4 clipToWorld, Rect viewport, out Vector3 outP)
{
// pixels to -1..1
Vector3 in_v;
in_v.x = (p.x - viewport.x) * 2.0f / viewport.width - 1.0f;
in_v.y = (p.y - viewport.y) * 2.0f / viewport.height - 1.0f;
// It does not matter where the point we unproject lies in depth; so we choose 0.95, which
// is further than near plane and closer than far plane, for precision reasons.
// In a perspective camera setup (near=0.1, far=1000), a point at 0.95 projected depth is about
// 5 units from the camera.
in_v.z = 0.95f;
Vector3 pointOnPlane;
if (clipToWorld.PerspectiveMultiplyPoint3(in_v, out pointOnPlane))
{
// Now we have a point on the plane perpendicular to the viewing direction. We need to return the one that is on the line
// towards this point, and at p.z distance along camera's viewing axis.
Vector3 cameraPos = cameraToWorld.GetPosition();
Vector3 dir = pointOnPlane - cameraPos;
// The camera/projection matrices follow OpenGL convention: positive Z is towards the viewer.
// So negate it to get into Unity convention.
Vector3 forward = -cameraToWorld.GetAxisZ();
float distToPlane = Vector3.Dot(dir, forward);
if (Mathf.Abs(distToPlane) >= 1.0e-6f)
{
bool isPerspective = clipToWorld.IsPerspective();
if (isPerspective)
{
dir *= p.z / distToPlane;
outP = cameraPos + dir;
}
else
{
outP = pointOnPlane - forward * (distToPlane - p.z);
}
return(true);
}
}
outP = new Vector3(0.0f, 0.0f, 0.0f);
return(false);
}
