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RaycastHit, triangleIndex, and submeshes - which submesh?
A raycast hit will give you the triangle index hit. What if the mesh has submeshes? There is no submesh index.
Is it ok to assume that the triangle list is sorted such that the submesh is the one modulo the number of vertices in preceding lists?
In other words, lets say submesh 0 has 10 verts, submesh 1 has 15 verts, and submesh 2 has 12 verts. And the raycast hit says 'triangle index 12'
Does that mean submesh 1? IOW submesh 0 is from 0-9, submesh 1 is 10-24, and submesh2 is 25-37?
How do I map a material to the submesh?
Answer by ScroodgeM · Jul 28, 2012 at 11:23 AM
- main mesh contains all triangles of this mesh and also all that can be accessed via submeshes.
submeshes contains tris that can be accessed also via main mesh
submeshes are always exists in any mesh, at least one
sum of all submeshes tris is equal to main mesh tris
submeshes are used to apply different materials to tris
so finally, when you got from raycast hit to triangle index 50, you should search it in main mesh (it contains all tris including triangle 50), then get vertices for this triangle, and find triangle with those vertices in submeshes
bonus: MeshAnaliser.cs
using UnityEngine; using System.Collections; public class MeshAnaliser : MonoBehaviour { void Update() { if (Input.GetMouseButtonDown(0)) { RaycastHit hit; if (Physics.Raycast(Camera.main.ScreenPointToRay(Input.mousePosition), out hit)) { Mesh m = GetMesh(gameObject); if (m) { int[] hittedTriangle = new int[] { m.triangles[hit.triangleIndex * 3], m.triangles[hit.triangleIndex * 3 + 1], m.triangles[hit.triangleIndex * 3 + 2] }; for (int i = 0; i < m.subMeshCount; i++) { int[] subMeshTris = m.GetTriangles(i); for (int j = 0; j < subMeshTris.Length; j += 3) { if (subMeshTris[j] == hittedTriangle[0] && subMeshTris[j + 1] == hittedTriangle[1] && subMeshTris[j + 2] == hittedTriangle[2]) { Debug.Log(string.Format("triangle index:{0} submesh index:{1} submesh triangle index:{2}", hit.triangleIndex, i, j / 3)); } } } } } } } static Mesh GetMesh(GameObject go) { if (go) { MeshFilter mf = go.GetComponent<MeshFilter>(); if (mf) { Mesh m = mf.sharedMesh; if (!m) { m = mf.mesh; } if (m) { return m; } } } return (Mesh)null; } }
Well that helps some. At least I could find which submesh tri list it's in. How does the submesh index correspond to the material? Is there some mapping somewhere? $$anonymous$$y own tests show that the first submesh is NOT necessarily the first material in the list
This line:
$$anonymous$$eshFilter mf = go.GetComponent();
should probably work better like this:
$$anonymous$$eshFilter mf = go.GetComponent<$$anonymous$$eshFilter>();
Damn that Qato!
@DaveA, you are right 8) thanks. Qato thinks that it was a tag 8)
@art , how did you test material-to-submesh mapping? all materials with submeshes are mapped one-to-one. of course, if submeshes quantity and materials quantity are the same. if materials quantity is more then submeshes, all extra materials are drawn with last submesh. if materials quantity less then submeshes, submeshes are not drawn.
I put a GUIText in and set the text of it to the triangle index (from the raycast hit, which comes from mouse position then screen-to-world) So mouse-over will tell me what triangle index I'm hitting. I also used Debug.DrawLine to hilight the triangle. I can see that if I'm on triangle 0, that it is not the first material in the list. I'll post screen shots tomorrow.
Answer by bbupton · Feb 10, 2015 at 10:36 PM
I ran some tests using a procedurally-generated mesh. As artie suspected in his original post, the triangle lists for the submeshes seem to be stored in order in the global triangle list. The ordering is determined by the submesh index, not the order of creation of the submeshes.
So if you do something like:
mesh.SetTriangles (submesh0, 0);
mesh.SetTriangles (submesh1, 1);
mesh.SetTriangles (submesh2, 2);
The full triangle list will consist of all the vertex indices for submesh0, followed by all the vertex indices for submesh1, followed by all the vertex indices for submesh2.