Unity3D: detect triangles of mesh intersects with other gameObject

Question

I'm have plane, contains multiple meshes (as usually). Now, I added to scene new gameObject - Cylinder. When cylinder collides with plane, I need to detect all triangles of plane, that appears inside of Cylinder. Is it possible with Unity3D API?
I saw tutorial "Colliders as Triggers", but I have one question - can I handle Trigger event without Rigidbody component in colliding objects? By some reasons I can't have Rigidbody in plane and in cylinder.

Answer 1

This can be accomplished by adding a spherecast to the cylinder and when any object enters it ( a box collider, raycast, etc ) have some event occur. For detecting the triangles of the plane ( assuming you have some sort of mesh collider ) you can get a list of all hit objects within the cylinder's spherecast and cycle through each one that composes a complete mesh triangle. Here's some code to show the process:

void GetMeshTriangle( RaycastHit meshHitPoint, MeshCollider meshObject ){
Mesh mesh = meshObject.sharedMesh;
Vector3[] vertices = mesh.vertices;
int[] triangles = mesh.triangles;
int counter = 0;
for( int n = 0; n <= ( worldObjectsHit.Length * 3 ); n++ ){
    if ( counter == 2 ){
        Transform hitTransform = meshHitPoint.collider.transform;
        try{
            Vector3 pointOne = vertices[triangles[meshHitPoint.triangleIndex * 3 + n]];
            Vector3 pointTwo = vertices[triangles[meshHitPoint.triangleIndex * 3 + ( n-1 )]];
            Vector3 pointThree = vertices[triangles[meshHitPoint.triangleIndex * 3 + ( n-2 )]];
            pointOne = hitTransform.TransformPoint( pointOne );
            pointTwo = hitTransform.TransformPoint( pointTwo );
            pointThree = hitTransform.TransformPoint( pointThree );
            Vector3 meshObjectCenter = new Vector3( ( ( pointOne.x + pointTwo.x + pointThree.x ) / 3 ), 
                                           ( ( pointOne.y + pointTwo.y + pointThree.y ) / 3 ) , 
                                           ( ( pointOne.z + pointTwo.z + pointThree.z ) / 3 ) );
            Debug.DrawLine( p0, p1 );
            Debug.DrawLine( p1, p2 );
            Debug.DrawLine( p2, p0 );
            IsMeshColliding( meshHitPoint, meshObjectCenter );
            } catch ( System.IndexOutOfRangeException ex ){
                break;
            }
            counter = 0;
        } else {
        counter++;
        }
    }
}

At the line "IsMeshColliding( )" you can add in your own logic to have some sort of event occur.