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Find out what's wrong with my instancing code

JustChris Member since: 11/9/2005 From: Chicago, IL, United States

Posted - 4/10/2009 3:58:26 AM

Normally I don't post this much code to focus on a problem, but I've been stumped for days on how to use mesh instancing correctly. The few instancing samples I've seen for DirectX have me still wondering how you should set up your vertex data for instance streams so that they are read correctly according to the vertex declaration. I used NVidia's instancing sample because the code looked clearer than other examples I've seen. Well, this is a bare bones version of the code I'm using but I think I stripped it down too far and probably missing some important things.

This code compiles without errors but I only see one instance of the mesh, and couldn't use Pix or debugging to help me figure out where I could be missing some function calls. My best guess is that the InstanceData vertex declaration isn't configured correctly. No shader files are being used here.

My vertex declarations, and matrix struct used for instancing data:

static D3DVERTEXELEMENT9 vertexN[] = 
{
	{0, 0,  D3DDECLTYPE_FLOAT3, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_POSITION, 0},
	{0, 12, D3DDECLTYPE_FLOAT3, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_NORMAL, 0},
	{0, 24, D3DDECLTYPE_D3DCOLOR, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_COLOR, 0},
	{0, 28, D3DDECLTYPE_FLOAT2, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_TEXCOORD, 0},
	D3DDECL_END()
};


const D3DVERTEXELEMENT9 InstanceData[] =
{
	{1, 0,  D3DDECLTYPE_FLOAT4, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_TEXCOORD, 1},
	{1, 16, D3DDECLTYPE_FLOAT4, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_TEXCOORD, 2},
	{1, 32, D3DDECLTYPE_FLOAT4, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_TEXCOORD, 3},
	{1, 48, D3DDECLTYPE_FLOAT4, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_COLOR,    0},
	D3DDECL_END()
};

struct MatrixVertex
	{
	MatrixVertex(D3DXVECTOR4& i1, D3DXVECTOR4& i2, D3DXVECTOR4&i3, D3DXVECTOR4&i4, D3DXCOLOR&c)
	: r1(i1),r2(i2),r3(i3),c1(c) {}
	D3DXVECTOR4 r1;     // row 1
	D3DXVECTOR4 r2;     // row 2
	D3DXVECTOR4 r3;	   // row 3
	D3DXCOLOR c1; // color
	};

Setup code

D3DXMATRIX* InstanceMatrices;
LPDIRECT3DVERTEXDECLARATION9 pMeshVertexDecl;
LPDIRECT3DVERTEXBUFFER9 MeshVB, ModelMatrixVB;
LPDIRECT3DINDEXBUFFER9  MeshIB;

// Loading the mesh from a file, it produces the set of vertices 
// to use in the vertex buffer

	TestMesh.loadfromOBJ("Data/test.obj");

	// Set up vertex declaration
	Display.D3Device()->CreateVertexDeclaration(vertexN, &pMeshVertexDecl);
	numInstances = 20;

	// Create the matrix vertex buffer
	Display.D3Device()->CreateVertexBuffer(numInstances * sizeof(MatrixVertex),
		D3DUSAGE_DYNAMIC | D3DUSAGE_WRITEONLY, 0, D3DPOOL_DEFAULT, &ModelMatrixVB, NULL);

	// Set up the instance matrices
	InstanceMatrices = new D3DXMATRIX[numInstances];

	// Lock the vertex buffer
	MatrixVertex* pVertices;
	ModelMatrixVB->Lock( 0, 0, (void**)&pVertices, D3DLOCK_DISCARD);
	for (unsigned i = 0; i < numInstances; i++) {

		pVertices[i].r1 = D3DXVECTOR4(1.0f, 0.0f, 0.0f, (float)i); // translate along X;
		pVertices[i].r2 = D3DXVECTOR4(0.0f, 1.0f, 0.0f, (float)i); // translate along Y;
		pVertices[i].r3 = D3DXVECTOR4(0.0f, 0.0f, 1.0f, 0.0f);
		pVertices[i].c1 = 0xffffffff;
	}
	ModelMatrixVB->Unlock();

	// Set index buffer indices
	// Allocating the number of vertices

	UINT *g_indices;
	g_indices = new UINT[TestMesh.verts().size()];  

	unsigned totalVertices = TestMesh.verts().size();
	for (unsigned i = 0; i < totalVertices; i++) {
		g_indices[i] = i;
	}

	// Create the mesh vertex buffer and index buffer
	Display.D3Device()->CreateVertexBuffer(totalVertices * sizeof(vertexN),
		D3DUSAGE_WRITEONLY, 0, D3DPOOL_MANAGED, &MeshVB, NULL );

	Display.D3Device()->CreateIndexBuffer(totalVertices * sizeof(UINT),
		D3DUSAGE_WRITEONLY, D3DFMT_INDEX32, D3DPOOL_MANAGED, &MeshIB, NULL);

	// Lock the mesh vertex buffer
	void *pData;
	MeshVB->Lock( 0, 0, (void**)&pData, 0);
	memcpy(pData, &(TestMesh.verts().at(0)), totalVertices * sizeof(vertexN)); 

	MeshVB->Unlock();

	// Lock the mesh index buffer

	MeshIB->Lock(0, 0, (void**)&pData, 0);
	memcpy(pData, g_indices, totalVertices * sizeof(UINT));

	MeshIB->Unlock();

Rendering code


	// Display setup code to start the scene...

	// Vertex declaration

	Display.D3Device()->SetVertexDeclaration(pMeshVertexDecl);


	// stream sources
	Display.D3Device()->SetStreamSourceFreq(0,(D3DSTREAMSOURCE_INDEXEDDATA | numInstances));
	Display.D3Device()->SetStreamSourceFreq(1,(D3DSTREAMSOURCE_INSTANCEDATA | 1));

	Display.D3Device()->SetStreamSource(0, MeshVB, 0, 
		D3DXGetDeclVertexSize(vertexN, 0));
	Display.D3Device()->SetStreamSource(1, ModelMatrixVB, 0,
		D3DXGetDeclVertexSize(InstanceData, 1));

	// Set index buffer to use
	Display.D3Device()->SetIndices(MeshIB); 

	// Display mesh and clean stream sources
	Display.D3Device()->DrawIndexedPrimitive(D3DPT_TRIANGLELIST, 0, 0, totalVertices, 
		0, totalVertices / 3);

	Display.D3Device()->SetStreamSourceFreq(0, 1);
	Display.D3Device()->SetStreamSourceFreq(1, 1);

	Display.D3Device()->EndScene();
	Display.D3Device()->Present(0, 0, 0, 0);

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