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I am trying to create an terrain using opentk/opengl.

I have a problem with the VBO/IBO. I think a picture of the problem is the best way to show it: the problem

I dont understand why the last triangle of a row connects to the first vertices of the row.

Here is the code:

int mapSize = 7; void CreateVertexBuffer() { Vector3[] vertices = new Vector3[(mapSize + 1) * (mapSize + 1)]; short[] indices = new short[ ((mapSize)*(mapSize)) * 6]; for (int x = 0; x < mapSize + 1 ; x++) { for (int y = 0; y < mapSize + 1 ; y++) { int li_offset = x * (mapSize + 1) + y; vertices[li_offset] = new Vector3(x / 4.0f, 0 , y / 4.0f); } } int index = 0; for (int x = 0; x < mapSize ; x++) { for (int y = 0; y < mapSize ; y++) { indices[index + 0] = (short)( x * (mapSize + 1) + y); indices[index + 1] = (short)(indices[index + 0] + mapSize + 2); indices[index + 2] = (short)(indices[index + 0] + mapSize + 1); indices[index + 3] = (short)(indices[index + 0]); indices[index + 4] = (short)(indices[index + 0] + 1); indices[index + 5] = (short)(indices[index + 0] + 2); index += 6; } } GL.GenBuffers(1, out vbo); GL.BindBuffer(BufferTarget.ArrayBuffer, vbo); GL.BufferData<Vector3>(BufferTarget.ArrayBuffer, new IntPtr(vertices.Length * Vector3.SizeInBytes), vertices, BufferUsageHint.StaticDraw); GL.GenBuffers(1, out ibo); GL.BindBuffer(BufferTarget.ElementArrayBuffer, ibo); GL.BufferData<short>(BufferTarget.ElementArrayBuffer, new IntPtr(indices.Length * sizeof(short) ), indices, BufferUsageHint.StaticDraw); }

How can I make the last row of triangles properly formed like all the others?

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  • \$\begingroup\$ This is just a wild guess, but if it's using triangle strips for rendering you might need to use a degenerate triangle at the end of each row, and zig-zag down. So if you numbered your quads in a 4xN it would go like 0,1,2,3, 7,6,5,4... \$\endgroup\$ Commented Jun 20, 2014 at 20:24

1 Answer 1

Reset to default
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Okay, after bug-searching for a while i came up with this, which works just fine. 

 void CreateVertexBuffer() { Vector3[] vertices = new Vector3[mapSize*mapSize]; short[] indices; for (int x = 0; x < mapSize; x++) { for (int z = 0; z < mapSize; z++) { vertices[x * mapSize + z] = new Vector3(x/10.0f,1.0f,z/10.0f); } } indices = new short[mapSize * mapSize * 6]; int index = 0; for (int x = 0; x < mapSize ; x++) { for (int z = 0; z < mapSize-1; z++) { int offset = x * mapSize + z; indices[index] = (short)(offset + 0); indices[index + 1] = (short)(offset + 1); indices[index + 2] = (short)(offset + mapSize); indices[index + 3] = (short)(offset + 1); indices[index + 4] = (short)(offset + mapSize + 1); indices[index + 5] = (short)(offset + mapSize); index += 6; } } GL.GenBuffers(1, out vbo); GL.BindBuffer(BufferTarget.ArrayBuffer, vbo); GL.BufferData<Vector3>(BufferTarget.ArrayBuffer, new IntPtr(vertices.Length * Vector3.SizeInBytes), vertices, BufferUsageHint.StaticDraw); GL.GenBuffers(1, out ibo); GL.BindBuffer(BufferTarget.ElementArrayBuffer, ibo); GL.BufferData<short>(BufferTarget.ElementArrayBuffer, new IntPtr(indices.Length * sizeof(short) ), indices, BufferUsageHint.StaticDraw); }
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