//----------------------------------------------------------------------------
// Title:       How to fake DX10 instancing on DX9 hardware
//
// Author:      Ivica Kolic
// E-mail:      Ivica.Kolic@gmail.com
//
// Copyright (c) Ivica Kolic. All rights reserved.
//
// Description: Code shows how to consturct DX9 alternative for 
//              DX10's "uint idx:SV_InstanceID" which is used for instancing.
//
//----------------------------------------------------------------------------



// GLOBAL VARIABLES:

    LPDIRECT3DVERTEXBUFFER9      _pInstanceVertexBuffer;    // Konstant vertex buffer used for instancing
    LPDIRECT3DVERTEXDECLARATION9 _pVertexDeclaration;       // Vertex declaration enriched with instancing index
    LPDIRECT3DDEVICE9            _d3dDevice;                // Rendering device


// SAMPLE OF VERTEX DECLARATION:

    const D3DVERTEXELEMENT9 vertexElements[] =
    {
        {0,  0, D3DDECLTYPE_FLOAT3, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_POSITION, 0},
        {0, 12, D3DDECLTYPE_FLOAT3, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_NORMAL,   0},
        {0, 24, D3DDECLTYPE_FLOAT2, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_TEXCOORD, 0},
        {1,  0, D3DDECLTYPE_FLOAT1, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_TEXCOORD, 1},   // This comes from instancing
        D3DDECL_END()
    };
    
    _d3dDevice->CreateVertexDeclaration( vertexElements, &_pVertexDeclaration );



// SETTING UP INSTANCING VERTEX BUFFER (CONSTANT):

    float instanceVertices[] = {0.0f, 1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f, 7.0f };
    
    _d3dDevice->CreateVertexBuffer( sizeof(instanceVertices), 0, 0, D3DPOOL_DEFAULT, &_pInstanceVertexBuffer, NULL );

    void* pVertices;
    
    _pInstanceVertexBuffer->Lock(0, sizeof(instanceVertices), &pVertices, 0);
    memcpy(pVertices, instanceVertices, sizeof(instanceVertices));
    _pInstanceVertexBuffer->Unlock();
    


// RENDERING (_iNumberOfInstances times):

    _pd3dDevice9->SetVertexDeclaration(_pVertexDeclaration);
    
    _pd3dDevice9->SetStreamSource(1, _pInstanceVertexBuffer, 0, sizeof(float));

    _pd3dDevice9->SetStreamSourceFreq(0, (D3DSTREAMSOURCE_INDEXEDDATA  | _iNumberOfInstances));
    _pd3dDevice9->SetStreamSourceFreq(1, (D3DSTREAMSOURCE_INSTANCEDATA | 1));

    RenderGeometry(); // this will set stream source 0 and indices...
    
    // Shut down instancing after rendering is done:
    _pd3dDevice9->SetStreamSourceFreq(0,1);
    _pd3dDevice9->SetStreamSourceFreq(1,1);



// SHADER PART:

    struct VS_P_N_T
    {
        float4 pos    : POSITION;
        float3 normal : NORMAL;
        float2 tex    : TEXCOORD0;
        float  idx    : TEXCOORD1; // idx comes from instancing vertex buffer filled with constants: 0, 1, 2, 3, 4, 5, 6, 7.
    };
    
    // "float idx : TEXCOORD1" is replacement for DX10's "uint idx:SV_InstanceID"