private void Pick(int sx, int sy)
{
var ray = _cam.GetPickingRay(new Vector2(sx, sy), new Vector2(ClientWidth, ClientHeight));
// transform the picking ray into the object space of the mesh
var invWorld = Matrix.Invert(_meshWorld);
ray.Direction = Vector3.TransformNormal(ray.Direction, invWorld);
ray.Position = Vector3.TransformCoordinate(ray.Position, invWorld);
ray.Direction.Normalize();
_pickedTriangle = -1;
float tmin;
if (!Ray.Intersects(ray, _meshBox, out tmin))
{
return;
}
tmin = float.MaxValue;
for (var i = 0; i < _meshIndices.Count / 3; i++)
{
var v0 = _meshVertices[_meshIndices[i * 3]].Position;
var v1 = _meshVertices[_meshIndices[i * 3 + 1]].Position;
var v2 = _meshVertices[_meshIndices[i * 3 + 2]].Position;
float t;
float u, v;
//if (!Ray.Intersects(ray, v0, v1, v2, out t)) continue;
if (!Ray.Intersects(ray, v0, v1, v2, out t, out u, out v))
{
continue;
}
// determine the actual picked point on the triangle
var p = v0 * (1.0f - u - v) + v1 * u + v2 * v;
// find the closest intersection, exclude intersections behind camera
if (!(t < tmin || t < 0))
{
continue;
}
tmin = t;
_pickedTriangle = i;
}
}