1

I am creating voxel-based game (Minecraft etc.) and I was wondering how to rotate chunk parts that are more complex than simple squares, like the sides of a cube are.

For example, I created a staircase by manually constructing the mesh from code by giving the script the x,y,z coordinates of the virtual cube the staircase should appear in.

Now, how must I change the vertex coordinates of the staircase mesh so it gets rotated 90 degrees? Keep in mind that I can’t just rotate the whole gameobject because the stairs would be part of a chunk’s mesh.

Part of the code (creates vertices for one side of a very simple two-step staircase):

List<Vector3> vertices = new List<Vector3>();


		int x = 4;
		int y = 0;
		int z = 3;
                
            int angle = 0;//0 = 0 degrees, 1 = 90, and so on.

		vertices.Add(new Vector3(x, y, z));
		vertices.Add(new Vector3(x, y + 1, z));
		vertices.Add(new Vector3(x + 0.5f, y + 1, z));
		vertices.Add(new Vector3(x + 0.5f, y + 0.5f, z));
		vertices.Add(new Vector3(x + 1, y + 0.5f, z));
		vertices.Add(new Vector3(x + 1, y, z));
2

Untested on my part, but I think you can just do:

  • center - Vector3 around which you want to rotate the submesh
  • v - a vertex to rotate
  • q - a Quaternion representing the rotation you want to do
v = q * (v - center) + center;

So cycle through the vertex positions in the submesh you want to rotate, and apply the above to each one.

3

If anyone is looking, this tool can rotate vertices of a mesh, and transform vertices using handle manipulation or directly entering the x,y,z coordinates of each vertex.
https://assetstore.unity.com/packages/slug/166155

it also has a bunch of other tools to further model your staircase or any object’s mesh.