CODEWITHSUNDEEP
c#unity-game-engine
imtouchk
imtouchk

Reputation: 41

Missing vertices in procedurally generated mesh in Unity

I am trying to procedurally generate a mesh made out of quads, but at the positive y and negative z edges half of the quad is not rendered at all. I can sort of see why it happens, but I don't know how to fix it.

    public void create(byte[,,] blocks) {
        for(int z = 0; z < 16; z++) {
            for(int y = 0; y < 16; y++) {
                for(int x = 0; x < 16; x++) {
                    if(x == 0) {
                        int CurrentCount = vertices.Count;
 
                        vertices.Add(new Vector3(x, y + 1f, z + 1f));
                        vertices.Add(new Vector3(x, y - 1f, z + 1f));
                        vertices.Add(new Vector3(x, y - 1f, z - 1f));
                        vertices.Add(new Vector3(x, y + 1f, z - 1f));
 
                        indices.Add(CurrentCount);
                        indices.Add(CurrentCount + 1);
                        indices.Add(CurrentCount + 2);
 
                        indices.Add(CurrentCount + 2);
                        indices.Add(CurrentCount);
                        indices.Add(CurrentCount + 3);
                    }
                }
            }
        }
    }

enter image description here

Upvotes: 0

Views: 396

Answers (1)

derHugo
derHugo

Reputation: 90629

Your problem is with the normals.

  • Triangle goes clockwise -> normal shows in your direction.

    enter image description here

  • Triangle goes counter-clockwise -> normal shows away from you => Due to backface culling it is not rendered

    enter image description here

What you are doing is defining all your vertices in clockwise order like

(CurrentCount + 3)--------(CurrentCount + 0)
       |                         |
       |                         |
       |                         |
(CurrentCount + 2)--------(CurrentCount + 1)

and then create one triangle with indices in clockwise order

indices.Add(CurrentCount);
indices.Add(CurrentCount + 1);
indices.Add(CurrentCount + 2);

But the other one with counter-clockwise index order

indices.Add(CurrentCount + 2);
indices.Add(CurrentCount);
indices.Add(CurrentCount + 3);

You can see this quite good when you a) enter the wire-frame mode and be move to the other side of the plane

enter image description here

It should rather be

indices.Add(CurrentCount);
indices.Add(CurrentCount + 1);
indices.Add(CurrentCount + 2);

indices.Add(CurrentCount);
indices.Add(CurrentCount + 2);
indices.Add(CurrentCount + 3);

which now constructs one correct plane facing the "right" side of the Unity world

enter image description here

Upvotes: 2

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