How do I check if the mouse is over a VISIBLE vertex?

Question

Hi, how do I check if the mouse is over a visible mesh vertex in the scene view. I can get the vertex under the mouse using the following code:

 using UnityEditor;
 using UnityEngine;
 
 [CustomEditor(typeof(Test))]
 public class TestEditor : Editor
 {
     private MeshFilter meshFilter = null;
     private void OnSceneGUI()
     {
         if (meshFilter == null)
         {
             meshFilter = ((Test)target).GetComponent<MeshFilter>();
         }
         for (int a = 0; a < meshFilter.sharedMesh.vertices.Length; a++)
         {
             Vector3 screenPoint = SceneView.currentDrawingSceneView.camera.WorldToScreenPoint(meshFilter.sharedMesh.vertices[a]);
             screenPoint.y = SceneView.currentDrawingSceneView.camera.pixelHeight - screenPoint.y;
             if (Event.current.mousePosition.x >= screenPoint.x - 5 && Event.current.mousePosition.x < screenPoint.x + 5 && Event.current.mousePosition.y >= screenPoint.y - 5 && Event.current.mousePosition.y < screenPoint.y + 5)
             {
                 //THE MOUSE IS OVER THIS VERTEX.
             }
         }
     }
 }

The above code only checks if the mouse is over the vertex, not if there is a triangle in the way. How do I check if there is a triangle in the way (raycasting?). Thanks :D

Answer 1

Answer by robertbu · Oct 01, 2014 at 10:07 AM

This is an ugly little problem, and I don't see an easy problem. For many meshes with shared vertices, you can do the process in reverse. That is, you Raycast(). The RaycastHit returns the triangle and the hit point. You can take a look at the three vertices (transformed into world space) forming the triangle and find the closest to the hit.point. You know the vertex is visible because the triangle used to find it is visible. But it is possible to construct meshes where the closest vertex is not part of the triangle that was hit...unusual, but possible.

For meshes that don't share vertices, if the Dot product between the normal of the vertex and the forward of the camera is positive, you know that vertex cannot be seen by the camera. This eliminates vertices, but it does not verify them. That is, it is possible for vertices with negative-value normals to be occluded.

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How do I check if the mouse is over a VISIBLE vertex?

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