DirectX 11:如何勾勒出边界框？

Question

在一个2d平台游戏中，我想要可视化我创建的边界框来帮助调试。如何在Visual C++ 2012中完成此操作？

Answer 1

首先定义一个简单的顶点结构：

struct Vertex
{
    D3DXVECTOR3 position; //a 3D point even in 2D rendering
};

现在，您可以创建顶点和索引数组：

Vertex *vertices;
unsigned long *indices = new unsigned long[5];
D3D11_BUFFER_DESC vertexBufferDesc, indexBufferDesc;
D3D11_SUBRESOURCE_DATA vertexData, indexData;

//create the vertex array
vertices = new Vertex[5];
if(!vertices)
{
    //handle error
}
//load the vertex array with data
vertices[0].position = D3DXVECTOR3(left, top, 0.0f);
vertices[1].position = D3DXVECTOR3(right, top, 0.0f);
vertices[2].position = D3DXVECTOR3(right, bottom, 0.0f);
vertices[3].position = D3DXVECTOR3(left, bottom, 0.0f);
vertices[4].position = D3DXVECTOR3(left, top, 0.0f);
//create the index array
indices = new unsigned long[5];
if(!indices)
{
    //handle error
}
//load the index array with data
for(i=0; i<5; i++)
    indices[i] = i;

并将它们加载到缓冲区中：

ID3D11Buffer *vertexBuffer, *indexBuffer;
HRESULT result;

//set up the description of the dynamic vertex buffer
vertexBufferDesc.Usage = D3D11_USAGE_DYNAMIC; //enables recreation and movement of vertices
vertexBufferDesc.ByteWidth = sizeof(Vertex) * 5;
vertexBufferDesc.BindFlags = D3D11_BIND_VERTEX_BUFFER;
vertexBufferDesc.CPUAccessFlags = D3D11_CPU_ACCESS_WRITE; //couples with dynamic
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 = device->CreateBuffer(&vertexBufferDesc, &vertexData, &vertexBuffer);
if(FAILED(result))
{
    //handle error
}

//set up the description of the static index buffer
indexBufferDesc.Usage = D3D11_USAGE_DEFAULT;
indexBufferDesc.ByteWidth = sizeof(unsigned long) * 5;
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 = device->CreateBuffer(&indexBufferDesc, &indexData, &indexBuffer);
if(FAILED(result))
{
    //handle error
}

设置要渲染的矩形，如下所示：

unsigned int stride = sizeof(Vertex);
unsigned int offset = 0;

deviceContext->IASetVertexBuffers(0, 1, &vertexBuffer, &stride, &offset);
deviceContext->IASetIndexBuffer(indexBuffer, DXGI_FORMAT_R32_UINT, 0);
deviceContext->IASetPrimitiveTopology(D3D11_PRIMITIVE_TOPOLOGY_LINESTRIP);

现在使用您选择的着色器进行渲染，记住将orthographic matrix传递给着色器而不是透视矩阵。瞧！矩形。但是你还不能移动它。为此，您必须定义另一个函数：

bool UpdateRectBuffers(ID3D11Buffer *vertexBuffer, ID3D11DeviceContext *deviceContext, float top, float left, float bottom, float right)
{
    Vertex *vertices;
    D3D11_MAPPED_SUBRESOURCE mappedResource;
    VertexType *verticesPtr;
    HRESULT result;

    //create a temporary vertex array to fill with the updated data
    vertices = new Vertex[5];
    if(!vertices)
    {
        return false;
    }
    vertices[0].position = D3DXVECTOR3(left, top, 0.0f);
    vertices[1].position = D3DXVECTOR3(right, top, 0.0f);
    vertices[2].position = D3DXVECTOR3(right, bottom, 0.0f);
    vertices[3].position = D3DXVECTOR3(left, bottom, 0.0f);
    vertices[4].position = D3DXVECTOR3(left, top, 0.0f);

    //lock the vertex buffer so it can be written to
    result = deviceContext->Map(vertexBuffer, 0, D3D11_MAP_WRITE_DISCARD, 0, &mappedResource);
    if(FAILED(result))
    {
        return false;
    }

    verticesPtr = (Vertex*)mappedResource.pData;

    //copy the data into the vertex buffer
    memcpy(verticesPtr, (void*)vertices, (sizeof(Vertex) * 5));

    deviceContext->Unmap(vertexBuffer, 0);
    delete [] vertices;
    vertices = 0;

    return true;
}

这段代码的依赖项是float top、float left、float right、float left、ID3D11DeviceContext *deviceContext和ID3D11Device *device。