[d3d9] Disable instancing for non-indexed draws

[K0bin]

Fixes #2473

https://learn.microsoft.com/en-us/windows/win32/direct3d9/efficiently-drawing-multiple-instances-of-geometry#drawing-non-indexed-geometry

The docs say the following about instancing with non-indexed draws:

This technique is not supported by hardware acceleration on any device. It is only supported by software vertex processing and will work only with vs_3_0 shaders.

It also seems to work differently in the non-indexed example with seemingly no way to set the instance count. On the other hand they also use DrawIndexedPrimitive in the example for non-indexed draws, so I don't really understand it.

The best I can deduce is that instancing is not supported for non-indexed draws. This probably needs to be tested on Windows.

[misyltoad]

@K0bin
In the MSDN article you mention, it is refering to D3DSTREAMSOURCE_INDEXEDDATA, not whether there is an index buffer used.

Look at the two examples, they both call SetIndices and DrawIndexedPrimitive but one does not set D3DSTREAMSOURCE_INDEXEDDATA.

Indexed Geometry Performance Comparison

if( SUCCEEDED( pd3dDevice->BeginScene() ) )
{
    // Set up the geometry data stream
    pd3dDevice->SetStreamSourceFreq(0,
                (D3DSTREAMSOURCE_INDEXEDDATA | g_numInstancesToDraw));
    pd3dDevice->SetStreamSource(0, g_VB_Geometry, 0,
                D3DXGetDeclVertexSize( g_VBDecl_Geometry, 0 ));

    // Set up the instance data stream
    pd3dDevice->SetStreamSourceFreq(1,
                (D3DSTREAMSOURCE_INSTANCEDATA | 1));
    pd3dDevice->SetStreamSource(1, g_VB_InstanceData, 0, 
                D3DXGetDeclVertexSize( g_VBDecl_InstanceData, 1 ));

    pd3dDevice->SetVertexDeclaration( ... );
    pd3dDevice->SetVertexShader( ... );
    pd3dDevice->SetIndices( ... );

    pd3dDevice->DrawIndexedPrimitive( D3DPT_TRIANGLELIST, 0, 0, 
                g_dwNumVertices, 0, g_dwNumIndices/3 );
    
    pd3dDevice->EndScene();
}

Non-Indexed Geometry Performance Comparison

if( SUCCEEDED( pd3dDevice->BeginScene() ) )
{
    // Set the divider
    pd3dDevice->SetStreamSourceFreq(0, 1);
    pd3dDevice->SetStreamSource(0, g_VB_Geometry, 0,
                D3DXGetDeclVertexSize( g_VBDecl_Geometry, 0 ));

    // Set up the instance data stream
    pd3dDevice->SetStreamSourceFreq(1, verticesPerInstance));
    pd3dDevice->SetStreamSource(1, g_VB_InstanceData, 0, 
                D3DXGetDeclVertexSize( g_VBDecl_InstanceData, 1 ));

    pd3dDevice->SetVertexDeclaration( ... );
    pd3dDevice->SetVertexShader( ... );
    pd3dDevice->SetIndices( ... );

    pd3dDevice->DrawIndexedPrimitive( D3DPT_TRIANGLELIST, 0, 0, 
                g_dwNumVertices, 0, g_dwNumIndices/3 );
    
    pd3dDevice->EndScene();
}

I think what we should be checking for is D3DSTREAMSOURCE_INDEXEDDATA.

[K0bin]

Needs more investigation

[K0bin]

I tested this on Windows and instancing indeed only happens with indexed draws.

cc @Joshua-Ashton