EDIT

Since I read what Mark H suggested (thanks a lot, I found it very useful) I think my question can become clearer structured this way:

Using XNA 4.0, I'm trying to draw a cube.

Im using this method:

GraphicsDevice.DrawUserIndexedPrimitives<VertexPositionColor>(
    PrimitiveType.LineList,
    primitiveList,
    0,  // vertex buffer offset to add to each element of the index buffer
    8,  // number of vertices in pointList
    lineListIndices,  // the index buffer
    0,  // first index element to read
    7   // number of primitives to draw
);

I got the code sample from this page which simply draw a serie of triangles. I want to modify this code in order to draw a cube. I was able to slitghly move the camera so I can have the perception of solidity, I set the vertex array to contain the 8 points defining a cube. But I can't fully understand how many primitives I have to draw (last parameter) for each of PrimitiveType.

So, I wasn't able to draw the cube (just some of the edges in a non-defined order).

More in detail:

to build the vertex index list, the sample used

// Initialize an array of indices of type short.
lineListIndices = new short[(points * 2) - 2];

// Populate the array with references to indices in the vertex buffer
for (int i = 0; i < points - 1; i++)
{
    lineListIndices[i * 2] = (short)(i);
    lineListIndices[(i * 2) + 1] = (short)(i + 1);
}

I'm ashamed to say I cannot do the same in the case of a cube.

• what has to be the size of the lineListIndices?
• how should I populate it? In which order?

And how do these things change when I use a different PrimitiveType?

In the code sample there are also another couple of calls which I cannot fully understand, which are:

// Initialize the vertex buffer, allocating memory for each vertex.
vertexBuffer = new VertexBuffer(graphics.GraphicsDevice, vertexDeclaration,
points, BufferUsage.None);

// Set the vertex buffer data to the array of vertices.
vertexBuffer.SetData<VertexPositionColor>(pointList);

and

vertexDeclaration = new VertexDeclaration(new VertexElement[]
  {
    new VertexElement(0, VertexElementFormat.Vector3, VertexElementUsage.Position, 0),
    new VertexElement(12, VertexElementFormat.Color, VertexElementUsage.Color, 0)
  }
);

that is, for VertexBuffer and VertexDeclaration I could not find and significant (monkey-like) guide. I reported them too because I think they could be involded in understanding things.

I think I also have to understand something related to the order the vertexes are stored in the array. But actually I have no clue of what I should learn to have this function drawing a cube. So, if anybody could point me to the right direction, it wil be appreciated.

Hope to have made myself clear this time