XNA4 DrawIndexedPrimitives vs DrawUserIndexedPrimitives

GraphicsDevice.DrawIndexedPrimitives
– 그래픽카드에 vertex와 index 정보를 초기화하고, 그것을 호출하여 Draw하는 방식

http://msdn.microsoft.com/en-us/library/microsoft.xna.framework.graphics.graphicsdevice.drawindexedprimitives.aspx



void InitializePrimitive()
{
// 중간생략…
            // Initialize our Vertex Declaration
            vertexDeclaration = new VertexDeclaration(new VertexElement[]
                {
                    new VertexElement(0, VertexElementFormat.Vector3, VertexElementUsage.Position, 0),
                    new VertexElement(12, VertexElementFormat.Vector3, VertexElementUsage.Normal, 0),
                    new VertexElement(24, VertexElementFormat.Vector2, VertexElementUsage.TextureCoordinate, 0)
                }
            );


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


            // Set the vertex buffer data to the array of vertices.
            vertexBuffer.SetData(vertices.ToArray());


            // Create an index buffer, and copy our index data into it.
            indexBuffer = new IndexBuffer(graphics.GraphicsDevice, typeof(ushort),
                                          indices.Count, BufferUsage.None);
            indexBuffer.SetData(indices.ToArray());
}

void DrawPrimitive()
{
// 중간생략…
            // Set our vertex declaration, vertex buffer, and index buffer.
            graphics.GraphicsDevice.SetVertexBuffer(vertexBuffer);
            graphics.GraphicsDevice.Indices = indexBuffer;        


            foreach (EffectPass pass in basicEffect.CurrentTechnique.Passes)
            {
                pass.Apply();
                int primitiveCount = indices.Count / 3;
                graphics.GraphicsDevice.DrawIndexedPrimitives(
                    PrimitiveType.TriangleList, 0, 0, vertices.Count, 0, primitiveCount);

            }
}




GraphicsDevice.DrawUserIndexedPrimitives
– 매 프레임마다 GPU로 vertex와 index 정보를 보내어 Draw 하는 방식
– vertex와 index 정보가 계속해서 바뀌는 경우에 사용 (그러나, DynamicVertexBuffer가 이것보다 좀 더 빠르다고 함)

http://msdn.microsoft.com/en-us/library/microsoft.xna.framework.graphics.graphicsdevice.drawuserindexedprimitives.aspx


void DrawPrimitive()
{
// 중간생략…
            foreach (EffectPass pass in basicEffect.CurrentTechnique.Passes)
            {
                pass.Apply();
                int primitiveCount = indices.Count / 3;
                graphics.GraphicsDevice.DrawUserIndexedPrimitives(
                    PrimitiveType.TriangleList, vertices.ToArray(), 0, vertices.Count,
                    indices.ToArray(), 0, primitiveCount);

            }
}