DirectX 11: How to outline a bounding box? [closed] - c++

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In a 2d platform game, I want to visualize the bounding box that I have created to aid debugging. How can I accomplish this in Visual C++ 2012?

Answer 1

First define a simple vertex structure:
struct Vertex
{
D3DXVECTOR3 position; //a 3D point even in 2D rendering
};
Now you can create vertex and index arrays:
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;
And load them into buffers:
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
}
Set up the rectangle to be rendered like this:
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);
Now render with the shader of your choice, remembering to pass the orthographic matrix to the shader instead of the perspective matrix. Voilà! Rectangle. But you can't move it yet... You have to define another function to do that:
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;
}
The dependencies of this code are float top, float left, float right, float left, ID3D11DeviceContext *deviceContext, and ID3D11Device *device.

Answer 2

As you did not described well what you are able to do already, my answer is based on some assumptions.
Assumptions
So, I'm assuming that
you are able to draw a sprite (i.e. a colored/textured rectangle, i.e. quad of vertices / duet of triangles)
you already have data, that defines bounding volume (in any of several ways)
and will not explain how to do it.
Possible solutions
Variant 1:
You don't need anything special to draw edges. "Edges" (straight lines) are just long and thin rectangles. So, you need to put 4 thin rectangles in place where your edges should be.
This way you can choose thickness, color of line and even use a texture (dotted lines, dashed lines, lines with pink kittens, etc.) or shader effects, like procedural coloring, smoothing, blur, etc. Anyway, you will likely need lines for your game.
Variant 2:
You can draw lines instead of triangles. Use "line list" primitive topology, instead of "triangle list". (See: ID3D11DeviceContext::IASetPrimitiveTopology(), D3D11_PRIMITIVE_TOPOLOGY_LINELIST).
This way you cannot customize things. But this is much easier.
Variant 3:
Draw rectangle in wireframe mode. Just set up rasterizer state's fill mode. See: ID3D11DeviceContext::RSSetState, D3D11_RASTERIZER_DESC::FillMode, D3D11_FILL_MODE::D3D11_FILL_WIREFRAME
You'll get edges of triangles, even that ones that are diagonals of rectangle. This way you cannot set up neither thickness, nor color. But this way is really, really simple.
Variant 4:
Use any 2D drawing library that will do Variant 1 for you. As D3DX is obsolete, it is not recommended to use D3DXLine anymore. You can try DirectX toolkit or any library available on web.
Obviously you'll get additional dependency.
P.S.
If my initial assumptions were incorrect, then you'll not get an answer here. No men on StackOverflow will explain you such basic things. To correct a situation:
There are zillion ways to draw a rectangle. Pick any tutorial online (Ex.: rastertek, braynzarsoft) to get an idea on what's happening in "Possible solutions" part of this answer.
There are zillion ways to calculate bounding rectangle for each of zillion ways of defining it. Note, that to define a rectangle in 2D space, you need at least 2 points. And to define a 2D point, you need 2 coordinate values. So 4 values per each rectangle. Google or pick a math book for additional info.
Hope it helps!