Get Material of individual triangle

Unity Engine
,
1

I have an object which has touchable and non-touchable areas.

I currently work this by splitting the object into two meshes in Blender before importing to Unity. To detect, I Raycast and if we hit the mesh designated ‘touchable’ then (do touchy stuff)…

This works but it’s not ideal. What I really want is to get the material of the individual triangle hit by Raycast, so I can use one object - with two different materials assigned to it for touchable and non-touchable surfaces.

I’ve tried

Var FaceIndex = hit.triangleIndex*3

But trying to get the material of the face with

FaceIndex.renderer.material gives an error.

Any pointers would be most welcome!

2

Depending on the type of object you are using, you may be able to use one mesh but have two different colliders for the touchable and non-touchable areas (or perhaps just not have a collider on the non-touchable area at all). You can compare the collider returned in the RaycastHit with a reference to the touchable collider:-

var hit: RaycastHit;

if (hit.collider == touchableCollider) {
   // Process the touch.
}
3

Thanks, I already scripted it using two different colliders but I’d prefer to be able to detect the material on the exact face - so I can use that material on as many different objects as I need without having to add or modify the code to include new checks for touchable colliders.

At the moment I am doing the check via colliders / object tag.

I can get the material of a hit collider, but not of an individual face unfortunately.

4

Same exact question for me… is there a solution ?
Some of my objects have several materials…

5

Unfortunately there is no direct way of doing this. However, RaycastHit has a member called triangleIndex. Using Mesh.GetTriangles, you can look through each submesh to find a matching triangle index. Assuming that your submeshes do not share any triangles, then you should only find the triangle once, and you’ll know the submesh index.

6

Ok, and the submesh index should be equal to the (picked) material index in the MeshRenderer material list.
got it, I try it now.
Thank you very much.

7 
public static int GetSubMeshIndex(Mesh mesh, int triangleIndex)
        {
            if (mesh.isReadable == false)
            {
                Debug.LogError("You need to mark model's mesh as Read/Write Enabled in Import Settings.", mesh);
                return 0;
            }

            int triangleCounter = 0;
            for (int subMeshIndex = 0; subMeshIndex < mesh.subMeshCount; subMeshIndex++)
            {
                var indexCount = mesh.GetSubMesh(subMeshIndex).indexCount;
                triangleCounter += indexCount / 3;
                if (triangleIndex < triangleCounter)
                {
                    return subMeshIndex;
                }
            }

            Debug.LogError(
                $"Failed to find triangle with index {triangleIndex} in mesh '{mesh.name}'. Total triangle count: {triangleCounter}",
                mesh);
            return 0;
        }
8

thanks so much . you save my time

9

Hello, I’m also studying how to get the material information of a triangle of the model in unity recently. Have you solved this problem?