Question

At last I have something displayed. Switched to using graphics.GraphicsDevice.DrawIndexedPrimitives … Next problem… Only one triangle is displayed. The data set is about 200 triangles. I formatted the data coming in to make sure every three consecutive vectors form a triangle face. These are irregular triangles forming an irregular shape. I don’t fully understand the indexing of the vertices. Looks like each 3 indices form a triangle. If that is so then the indices match the data coming in. I did this:

int i4 = -1;
        indices = new int[xData1.Count];
        for (int i2 = 0; i2 < xData1.Count; i2++)
        {
            i4++;
            cubeVertices[i4].Position = new Vector3((float)xData1[i2][0], (float)xData1[i2][1], (float)xData1[i2][2]);
            cubeVertices[i4].Color = Color.LawnGreen;
            indices[i4] = i4;
        }

making the indices match the vertices coming in.. then I used Reimers normal calc to provide normals.. this is probably wrong as his example was using 6 vertices per index (I think!), like this:

for (int i = 0; i < cubeVertices.Length; i++)
            cubeVertices[i].Normal = new Vector3(0, 0, 0);

        for (int i = 0; i < indices.Length / 3; i++)
        {
            int index1 = indices[i * 3];
            int index2 = indices[i * 3 + 1];
            int index3 = indices[i * 3 + 2];

            Vector3 side1 = cubeVertices[index1].Position - cubeVertices[index3].Position;
            Vector3 side2 = cubeVertices[index1].Position - cubeVertices[index2].Position;
            Vector3 normal = Vector3.Cross(side1, side2);

            cubeVertices[index1].Normal += normal;
            cubeVertices[index2].Normal += normal;
            cubeVertices[index3].Normal += normal;
        }

        for (int i = 0; i < cubeVertices.Length; i++)
            cubeVertices[i].Normal.Normalize();

how many things do I need to fix here? I am only seeing 1 out of a couple of hundred triangles
🙁
thx for your patience

public struct VertexPositionColorNormal
    {
        public Vector3 Position;
        public Color Color;
        public Vector3 Normal;

        public readonly static VertexDeclaration VertexDeclaration = new VertexDeclaration
        (
            new VertexElement(0, VertexElementFormat.Vector3, VertexElementUsage.Position, 0),
            new VertexElement(sizeof(float) * 3, VertexElementFormat.Color, VertexElementUsage.Color, 0),
            new VertexElement(sizeof(float) * 3 + 4, VertexElementFormat.Vector3, VertexElementUsage.Normal, 0)
        );
    }

…

private void CopyToBuffers()
    {
        vertexBuffer = new VertexBuffer(graphics.GraphicsDevice, VertexPositionColorNormal.VertexDeclaration, 
            cubeVertices.Length, BufferUsage.WriteOnly);
        vertexBuffer.SetData(cubeVertices);

        myIndexBuffer = new IndexBuffer(graphics.GraphicsDevice, typeof(int), indices.Length, BufferUsage.WriteOnly);
        myIndexBuffer.SetData(indices);
    }

….

foreach (EffectPass pass in basicEffect.CurrentTechnique.Passes)
        {
            basicEffect.World = world;
            basicEffect.View = view;
            basicEffect.Projection = proj;

            pass.Apply();

            graphics.GraphicsDevice.Indices = myIndexBuffer;
            graphics.GraphicsDevice.SetVertexBuffer(vertexBuffer);
            graphics.GraphicsDevice.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0,
                cubeVertices.Length, 0, indices.Length / 3);

Answer 1

Your normal calculation is correct, and even if it was wrong the only thing that would happen is that your triangles would receive the wrong lightning.

You’re using indices which exactly match the order of the vertices coming in, which is in itself redundant. If you switch to not setting the indices at all and use DrawPrimitives instead with the primitive count the same does that make a difference?

Other than that, are you sure that the data you’re giving it is valid? Are the vertex positions correctly set?