不使用memcpy的DirectX11映射顶点

Question

apparently I have some issue regarding mapping vertexBuffers into the GPU using memcpy

This is my initial code

  D3D11_MAPPED_SUBRESOURCE MappedResource;
  ID3D11Buffer *pBuffer = s_vertexBuffers.pBuffers[i].Get();
  HRESULT hr = s_d3dContext->Map(pBuffer, 0, D3D11_MAP_WRITE_DISCARD, 0, &MappedResource);

  float *vertices = (float *) MappedResource.pData,
        *data = (float *)s_vertexBuffers.pData[i];
  int len = s_vertexBuffers.pStrides[i];
  if (i != VERTEX_BUFFER::COLOR)
  {
      len *= total;
  }

  memcpy(vertices, data, len);
  s_d3dContext->Unmap(pBuffer, 0);

What I'm going to change is the way of mapping (copying data from buffers into GPU) using pointer, like the one pointed on here into something similar to SetShaderParameters function (also on the tutorial), which is using pointer to get the data in the buffer and copying data directly using pointer into it

Basically, line float *vertices = (float *) MappedResource.pData until memcpy(vertices, data, len);

will be changed into something like the above tutorial pointed out

This is what my code looks like right now

VertexBuffers *dataPtr;
dataPtr = (VertexBuffers *)MappedResource.pData;
dataPtr->pBuffers[i] = s_vertexBuffers.pBuffers[i].Get();
dataPtr->pData[i] = s_vertexBuffers.pData[i];
dataPtr->pSizes[i] = s_vertexBuffers.pSizes[i];
dataPtr->pStrides[i] = s_vertexBuffers.pStrides[i];
if (i != VERTEX_BUFFER::COLOR) 
{
   dataPtr->pStrides[i] *= total;
}

struct VertexBuffers and VERTEX_BUFFER namespace content is

namespace VERTEX_BUFFER
{
    enum : int
    {
        POSITION,
        COLOR,
        TEXCOORD,
        COUNT
    };
}


 struct VertexBuffers
    {
        ComPtr<ID3D11Buffer>    pBuffers[VERTEX_BUFFER::COUNT];
        void*                   pData[VERTEX_BUFFER::COUNT];
        UINT                    pStrides[VERTEX_BUFFER::COUNT];
        UINT                    pSizes[VERTEX_BUFFER::COUNT];
    };

I think the problem is whenever I'm trying to copy data using pointer, I'm not taking len into account like memcpy does

Since I'm currently learning DirectX and programming please do correct me if something quite not right about my explanations.

Sorry for the bad code and bad programming skills, and also for the bad english, Cheers!

Answer 1

So you want something like this?

VertexBuffers *dataPtr;
dataPtr = (VertexBuffers *)MappedResource.pData;
dataPtr->pBuffers[i] = s_vertexBuffers.pBuffers[i].Get();
dataPtr->pSizes[i] = s_vertexBuffers.pSizes[i];
dataPtr->pStrides[i] = s_vertexBuffers.pStrides[i];
if (i != VERTEX_BUFFER::COLOR) 
{
   dataPtr->pStrides[i] *= total;
}
memcpy(dataPtr->pData[i], s_vertexBuffers.pData[i], dataPtr->pStrides[i]);

As you've found out when you have two pointers (say p and q) then all p = q; does is copy the pointer. If you want to copy the data that is being pointed to you should write memcpy(p, q, size_of_data); .