Search Unity

Help Wanted Reorder mesh triangles

Discussion in 'General Graphics' started by MatheusMarkies, Sep 16, 2021.

  1. MatheusMarkies


    Apr 16, 2017
    Good Morning!

    My problem is: I need to get the vertices of a mesh and send them to a shader.

    Inside the shader I will reassemble the mesh from its vertices.

    So far so good, I send the information and the shader tries to mount. But I'm not hitting the algorithm that assembles the new triangles. As seen in these images:


    Triangles (Made by shader):

    Each line of equal color; represents a triangle. Some colors end up repeating themselves, but I think you can understand.

    Basically I build a list already in the order of the triangles and then put together 3 by 3.

    Code (CSharp):
    2. public void buildObjectList()
    3. {
    4.     int indicesCount = 0;
    5.     int verticesCount = 0;
    7.         int[] triangles;
    8.         Vector3[] vertices;
    10.         triangles = pto.objectMesh.triangles;//Take a sequence of vertices that form a triangle.
    11.         vertices = pto.objectMesh.vertices;//Take vertex list
    13.         pto._pathTracingObject.indicesOffset = indicesCount;//Offset: Where the list of indices belonging to the object starts. | indicesCount: How many indices were added before these.
    14.         pto._pathTracingObject.indicesCount = triangles.Length;//How many indexes does this object have.
    16.         foreach (Vector3 vertice in vertices)
    17.             this.vertices.Add(vertice);
    19.         for (int i = 0; i < triangles.Length; i++)
    20.         {
    21.             this.indices.Add(triangles[i] + verticesCount + 1);//Variable containing all indices of all objects in the scene. | triangles[i] (take an index) +verticesCount(Add to the amount of vetices already added) + 1
    23.             /*Example:
    24.             If the previous object has 270 vertices.
    25.             The first triangle of the next objects will be connected to the vertices(271, 272, 273) instead of(0,1,2).
    26.             +1 because vertex 270 belongs to a different object.*/
    27.         }
    29.         indicesCount += triangles.Length;//update index
    30.         verticesCount += vertices.Length;//update index
    31. }
    In other words, if vertices 1,2 and 3 form a triangle in the list, they will appear in this sequence.
    So, when I need to form a triangle, I'll get the indices i, i+1 and i+2 from the list.

    As done here:

    Code (CSharp):
    2. Vector3 v0 = vertices[indices[pto._pathTracingObject.indicesOffset + i]];
    3.    Vector3 v1 = vertices[indices[pto._pathTracingObject.indicesOffset + i + 1]];
    4.    Vector3 v2 = vertices[indices[pto._pathTracingObject.indicesOffset + i + 2]];
    "pto._pathTracingObject.indicesOffset" It's good for when I have more than one object in the scene, then I skip the vertices of other objects using this offset.

    For example if I have 2 objects in the scene and the first has 10 vertices, the vertices of the second will be counted after those 10.

    Like this: 11.12,13...

    But this algorithm is wrong, as it is connecting vertices that shouldn't be together. "buildObjectList()"

    For example, unity says my cube has 12 triangles. However, the algorithm returned 716 triangles.