Question

im kinda stuck and i don’t know exactly where my problem might be. I am rendering a terrain divided by a quad tree. Now i am trying to make the boundaries of this quad tree visible for debugging purposes. Therefore im setting up a new buffer for each node on the terrain and only those debug quads wich are visible should be getting rendered. The problem i have is, that i am passing those node buffers to a method of another class (DebugTreeClass) by reference to create those there. But it seems like those buffers stay empty after the call of the method.
Here are my definitions:

1. m_debugTree->InitializeBuffer(node->vertexBufferDebug, node->indexBufferDebug, node->positionX, node->positionZ, node->width, device);

2. bool InitializeBuffer(ID3D11Buffer*,ID3D11Buffer*, float, float, float,ID3D11Device*);

And this is the method creating the index / vertex buffer:

bool DebugTreeClass::InitializeBuffer(ID3D11Buffer* vertexBuffer,ID3D11Buffer* indexBuffer, float positionX, float positionZ, float width, ID3D11Device* deviceContext){
VertexType* vertices;
unsigned long* indices;
int index, i, j;
D3D11_BUFFER_DESC vertexBufferDesc, indexBufferDesc;
D3D11_SUBRESOURCE_DATA vertexData, indexData;
HRESULT result;

m_vertexCount = 8; // to form a quad with lines we need 24 points.

m_indexCount = 24;

// Create the vertex array.
vertices = new VertexType[m_vertexCount];
if(!vertices)
{
    return false;
}

// Create the index array.
indices = new unsigned long[m_indexCount];
if(!indices)
{
    return false;
}

//DEFINE THE 8 POINTS FOR THE QUAD
//UPPER LEFT
vertices[0].position = D3DXVECTOR3(positionX, width / 2, positionZ);
vertices[0].color = D3DXVECTOR4(1.0f, 1.0f, 1.0f, 1.0f);
// UPPER RIGHT
vertices[1].position = D3DXVECTOR3(positionX + width, width / 2, positionZ);
vertices[1].color = D3DXVECTOR4(1.0f, 1.0f, 1.0f, 1.0f);
// BOTTOM RIGHT
vertices[2].position = D3DXVECTOR3(positionX + width, -(width / 2), positionZ);
vertices[2].color = D3DXVECTOR4(1.0f, 1.0f, 1.0f, 1.0f);
// BOTTOM LEFT
vertices[3].position = D3DXVECTOR3(positionX, -(width / 2), positionZ);
vertices[3].color = D3DXVECTOR4(1.0f, 1.0f, 1.0f, 1.0f);
// UPPER LEFT BACKSIDE
vertices[4].position = D3DXVECTOR3(positionX, width / 2, positionZ + width);
vertices[4].color = D3DXVECTOR4(1.0f, 1.0f, 1.0f, 1.0f);
// UPPER RIGHT BACKSIDE
vertices[5].position = D3DXVECTOR3(positionX + width, width / 2, positionZ + width);
vertices[5].color = D3DXVECTOR4(1.0f, 1.0f, 1.0f, 1.0f);
// BOTTOM RIGHT BACKSIDE
vertices[6].position = D3DXVECTOR3(positionX + width, -(width / 2), positionZ + width);
vertices[6].color = D3DXVECTOR4(1.0f, 1.0f, 1.0f, 1.0f);
// BOTTOM LEFT BACKSIDE
vertices[7].position = D3DXVECTOR3(positionX, -(width / 2), positionZ + width);
vertices[7].color = D3DXVECTOR4(1.0f, 1.0f, 1.0f, 1.0f);

//SET UP THE INDEXBUFFER
indices[0] = 0;
indices[1] = 1;
indices[2] = 1;
indices[3] = 2;
indices[4] = 2;
indices[5] = 3;
indices[6] = 3;
indices[7] = 0;
indices[8] = 0;
indices[9] = 4;
indices[10] = 1;
indices[11] = 5;
indices[12] = 2;
indices[13] = 6;
indices[14] = 3;
indices[15] = 7;
indices[16] = 4;
indices[17] = 5;
indices[18] = 5;
indices[19] = 6;
indices[20] = 6;
indices[21] = 7;
indices[22] = 7;
indices[23] = 4;

// Set up the description of the static vertex buffer.
vertexBufferDesc.Usage = D3D11_USAGE_DEFAULT;
vertexBufferDesc.ByteWidth = sizeof(VertexType) * m_vertexCount;
vertexBufferDesc.BindFlags = D3D11_BIND_VERTEX_BUFFER;
vertexBufferDesc.CPUAccessFlags = 0;
vertexBufferDesc.MiscFlags = 0;
vertexBufferDesc.StructureByteStride = 0;

// Give the subresource structure a pointer to the vertex data.
vertexData.pSysMem = vertices;
vertexData.SysMemPitch = 0;
vertexData.SysMemSlicePitch = 0;

// Now create the vertex buffer.
result = deviceContext->CreateBuffer(&vertexBufferDesc, &vertexData, &vertexBuffer);
if(FAILED(result))
{
    return false;
}

// Set up the description of the static index buffer.
indexBufferDesc.Usage = D3D11_USAGE_DEFAULT;
indexBufferDesc.ByteWidth = sizeof(unsigned long) * m_indexCount;
indexBufferDesc.BindFlags = D3D11_BIND_INDEX_BUFFER;
indexBufferDesc.CPUAccessFlags = 0;
indexBufferDesc.MiscFlags = 0;
indexBufferDesc.StructureByteStride = 0;

// Give the subresource structure a pointer to the index data.
indexData.pSysMem = indices;
indexData.SysMemPitch = 0;
indexData.SysMemSlicePitch = 0;

// Create the index buffer.
result = deviceContext->CreateBuffer(&indexBufferDesc, &indexData, &indexBuffer);
if(FAILED(result))
{
    return false;
}

// Release the arrays now that the buffers have been created and loaded.
delete [] vertices;
vertices = 0;

delete [] indices;
indices = 0;

return true;

}

There are 2 classes, the “QuadTreeClass” where the nodes get defined and the “DebugTreeClass” where the buffers for each node should get filled and the rendering of the debug quads take place.
If im debugging the “DebugTreeClass::InitializeBuffer()” method i can see that the buffers should get created successfully, so im pretty sure that something is wrong with the passing by reference to this method. Maybe im just blind….

Thanks for any help.

Answer 1

I’m pretty sure the problem is here:

bool DebugTreeClass::InitializeBuffer(ID3D11Buffer* vertexBuffer,...
...
result = deviceContext->CreateBuffer(&vertexBufferDesc, &vertexData, &vertexBuffer)

You are probably expecting the vertexBuffer to arrive in the caller of “InitializeBuffer”, but that doesn’t happen. You are talking about references, but you are not actually passing a reference. This will probably fix it:

bool DebugTreeClass::InitializeBuffer(ID3D11Buffer*& vertexBuffer,...

Same for the other pointers that you want to return.

Your original version copied the old (probably uninitialized — you should enable warnings) pointer variable from the caller into the “vertexBuffer” variable of the function, and used that. “vertexBuffer” was a local variable for the function, it never got passed back.

With my change, it is turned into a “reference to a pointer”. Now, the “vertexBuffer” pointer is actually the same pointer as the one passed into the function call, using the same memory. So, when you change that pointer, the version in caller is changed.