Changing Y Value in Vertex Array?

Question

I was working from a tutorial on procedural mesh generation, and I decided to try something out. I wanted to go through the array of points that I had created and make their Y values all 1. However, the program didn't really seem to do anything. Here's the program:

 public class ProceduralMesh : MonoBehaviour {
 
     Mesh mesh;
 
     Vector3[] vertices;
     int[] triangles;
 
     void Awake () {
         mesh = GetComponent<MeshFilter>().mesh;
     }
 
     // Use this for initialization
     void Start () {
         MakeMeshData();
         CreateMesh();
 
         for (int i = 0; i < vertices.Length; i++)
         {
             vertices[i].y = 1;
         }
     }
     
     // Update is called once per frame
     void MakeMeshData () {
         //Create array of verts
         vertices = new Vector3[] {new Vector3 (0, 0, 0), new Vector3 (0, 0, 1), new Vector3 (1, 0, 0), new Vector3 (1, 0, 1)};
         //Create array of ints
         triangles = new int[] {0, 1, 2, 2, 1, 3};
     }
 
     void CreateMesh () {
         mesh.Clear();
         mesh.vertices = vertices;
         mesh.triangles = triangles;
 
         mesh.RecalculateNormals();
     }
 }

The for loop is what I was using to make it go through the list. Basically, the mesh just stayed at y = 0. It's probably something super simple, but all help would be gratefully received:)

Answer 1

Answer by Tobychappell · May 30, 2018 at 01:12 AM

On the mesh object you wish to Edit, you want to call SetVertices and pass the collection of vertices.

https://docs.unity3d.com/ScriptReference/Mesh.SetVertices.html

After doing so you would need to tell the mesh to recalculate it's normals

https://docs.unity3d.com/ScriptReference/Mesh.RecalculateNormals.html

If you're going to be updating the mesh a lot, you'd be able to increase/save performance by calling the MarkDynamic method on the mesh object.

https://docs.unity3d.com/ScriptReference/Mesh.MarkDynamic.html

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Tobychappell · May 30, 2018 at 01:31 AM 0

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I'm not 100% sure on this, but in your code the array of verts is the same array of vests in the mesh object. When you're setting y to be 1, that mesh is seeing that change, however this data hasn't been sent to the GPU, it would be bad to update the mesh vertex data every time a single vert was changed as that would consume allot more of the bandwidth between cpu and gpu. Hence MarkDynamic, not really sure what that does under the hood, but I guess it optimises the way it'll communicate with the GPU for this mesh. Again I'm not a graphics engineer, this is more of a gut feeling of WHY your mesh wasn't updating.

Winj42 · May 30, 2018 at 05:55 PM 0

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OH SICK!! Thank you so much! Do you know how exactly to use that SetVertices? I can't quite figure it out...

ShadyProductions Winj42 · May 30, 2018 at 06:02 PM 2

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 mesh.SetVertices(vertices);
 mesh.RecalculateNormals();

Or a quicker fix, you can simply call 'CreateMesh()' after you set the vertices y.

Winj42 ShadyProductions · May 31, 2018 at 01:04 PM 0

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WOW HAHA I cannot believe that I didn't think of calling CreateMesh() after setting the vertices! Thank you so much!!

Changing Y Value in Vertex Array?

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