As I prefer to camp in the managed world I couldn’t resist to download the new XNA beta. I must confess that I was less interested in the Game Studio. I was locking for what Microsoft had done with MDX 2. The first impression wasn’t that bad as it looks very similar to what we have seen in MDX 1 and 2. Even if there are some leftovers the fixed function are gone as announced. Some classes are renamed but that’s fine. I like the step that gives us properties for the old descriptions structures. The new effect framework looks very similar what I am already have seen for Direct3D 10. Good work guys.

But with light comes shadows. I really don’t like that the have cut the possibility to lock and unlock resources. This makes dynamic resources less effective. Remove most of Direct3DX doesn’t make me happy too. This reduces the use of the XNA framework to write tools.

As this is only the first impression on a first beta I am still undecided how useful the final version would be for me. If I will not be happy at the end I still could use MDX 1 or write my own wrapper.

Last night I spend some time on my managed layer for Direct3D 10. It’s nearly complete and therefore I start playing with some advanced features. One thing I never really like since Direct3D 9 was the need to define your vertex structure twice. One time for the compiler and then for Direct3D again. It’s still the same for D3D10. The name has changed from vertex declaration to input layout. Some other details have changed too but the pain to do it twice is still there.

C++:

struct SimpleVertex

{

    D3DXVECTOR3 Pos; 

    D3DXVECTOR4 Color;

};

To create and set the input layout for this structure the following code is necessary.

// Define the input layout

D3D10_INPUT_ELEMENT_DESC layout[] =

{

    { "POSITION", 0, DXGI_FORMAT_R32G32B32_FLOAT, 0, 0, D3D10_INPUT_PER_VERTEX_DATA, 0 }, 

    { "COLOR", 0, DXGI_FORMAT_R32G32B32A32_FLOAT, 0, 12, D3D10_INPUT_PER_VERTEX_DATA, 0 },

};

UINT numElements = sizeof(layout)/sizeof(layout[0]);

// Create the input layout

D3D10_PASS_DESC PassDesc;

g_pTechnique->GetPassByIndex( 0 )->GetDesc( &PassDesc );

hr = g_pd3dDevice->CreateInputLayout( layout, numElements, PassDesc.pIAInputSignature, PassDesc.IAInputSignatureSize, &g_pVertexLayout );

if( FAILED(hr) )

    return hr;

// Set the input layout

g_pd3dDevice->IASetInputLayout( g_pVertexLayout );

This can easily be ported to C#:

struct SimpleVertex

{

    public SimpleVertex(DXGI.R32G32B32Float position, DXGI.R32G32B32A32Float color)

    {

        this.position = position;

        this.color = color;

    }

    DXGI.R32G32B32Float position;

    DXGI.R32G32B32A32Float color;

}

// Define the input layout

D3D10.InputElement[] layout = new D3D10.InputElement[]

{

    new D3D10.InputElement ("position", 0, DXGI.Format.R32G32B32Float, 0, 0, D3D10.InputClassification.PerVertexData, 0),

    new D3D10.InputElement ("color", 0, DXGI.Format.R32G32B32A32Float, 0, 12, D3D10.InputClassification.PerVertexData, 0)

};

// Create the input layout

inputLayout = new D3D10.InputLayout(device, layout, technique.Passes[0].InputAssemblerSignature);

// Set the input layout

device.InputAssembler.InputLayout = inputLayout;

Clever usage of propertys save some lines of code but the main problem is still the same. Let’s add some reflection magic.

// Create the input layout

inputLayout = new D3D10.InputLayout(device, typeof(SimpleVertex), technique.Passes[0].InputAssemblerSignature);

// Set the input layout

device.InputAssembler.InputLayout = inputLayout;

This new construtor I add last night use reflection to analyse the vertex structure and create the nessary layout on the fly. If you change the structure the layout will be automatically in sync.