3D bounding box
- Get given GameObject 3D bounding box's center and size
- Compute 8 corners
- Transform positions to GUI space (screen space)
Function GUI3dRectWithObject
will return the 3D bounding box of given GameObject on screen.
2D bounding box
- Iterate through every vertex in a given GameObject
- Transform every vertex's position to world space, and transform to GUI space (screen space)
- Find 4 corner value: x1, x2, y1, y2
Function GUI2dRectWithObject
will return the 2D bounding box of given GameObject on screen.
Code
public static Rect GUI3dRectWithObject(GameObject go)
{
Vector3 cen = go.GetComponent<Renderer>().bounds.center;
Vector3 ext = go.GetComponent<Renderer>().bounds.extents;
Vector2[] extentPoints = new Vector2[8]
{
WorldToGUIPoint(new Vector3(cen.x-ext.x, cen.y-ext.y, cen.z-ext.z)),
WorldToGUIPoint(new Vector3(cen.x+ext.x, cen.y-ext.y, cen.z-ext.z)),
WorldToGUIPoint(new Vector3(cen.x-ext.x, cen.y-ext.y, cen.z+ext.z)),
WorldToGUIPoint(new Vector3(cen.x+ext.x, cen.y-ext.y, cen.z+ext.z)),
WorldToGUIPoint(new Vector3(cen.x-ext.x, cen.y+ext.y, cen.z-ext.z)),
WorldToGUIPoint(new Vector3(cen.x+ext.x, cen.y+ext.y, cen.z-ext.z)),
WorldToGUIPoint(new Vector3(cen.x-ext.x, cen.y+ext.y, cen.z+ext.z)),
WorldToGUIPoint(new Vector3(cen.x+ext.x, cen.y+ext.y, cen.z+ext.z))
};
Vector2 min = extentPoints[0];
Vector2 max = extentPoints[0];
foreach (Vector2 v in extentPoints)
{
min = Vector2.Min(min, v);
max = Vector2.Max(max, v);
}
return new Rect(min.x, min.y, max.x - min.x, max.y - min.y);
}
public static Rect GUI2dRectWithObject(GameObject go)
{
Vector3[] vertices = go.GetComponent<MeshFilter>().mesh.vertices;
float x1 = float.MaxValue, y1 = float.MaxValue, x2 = 0.0f, y2 = 0.0f;
foreach (Vector3 vert in vertices)
{
Vector2 tmp = WorldToGUIPoint(go.transform.TransformPoint(vert));
if (tmp.x < x1) x1 = tmp.x;
if (tmp.x > x2) x2 = tmp.x;
if (tmp.y < y1) y1 = tmp.y;
if (tmp.y > y2) y2 = tmp.y;
}
Rect bbox = new Rect(x1, y1, x2 - x1, y2 - y1);
Debug.Log(bbox);
return bbox;
}
public static Vector2 WorldToGUIPoint(Vector3 world)
{
Vector2 screenPoint = Camera.main.WorldToScreenPoint(world);
screenPoint.y = (float)Screen.height - screenPoint.y;
return screenPoint;
}
Reference: Is there an easy way to get on-screen render size (bounds)?