Directx11 heightmap texture real-time modification problem - game-development

Question

I'm making a terrain tool.
I made a 2D texture and am using it as a height map.
I want to change a specific part of the heightmap, but I'm having a problem.
I changed certain small parts, but the whole landscape of the texture is changed.
I would like to know the cause of this problem and how to solve it
thank you.
`HeightMap ShaderResourceView Create Code
void TerrainRenderer::BuildHeightmapSRV(ID3D11Device* device)
{
ReleaseCOM(mHeightMapSRV);
ReleaseCOM(m_hmapTex);
D3D11_TEXTURE2D_DESC texDesc;
texDesc.Width = m_terrainData.HeightmapWidth; //basic value 2049
texDesc.Height = m_terrainData.HeightmapHeight; //basic value 2049
texDesc.MipLevels = 1;
texDesc.ArraySize = 1;
texDesc.Format = DXGI_FORMAT_R16_FLOAT;
texDesc.SampleDesc.Count = 1;
texDesc.SampleDesc.Quality = 0;
texDesc.Usage = D3D11_USAGE_DYNAMIC;
texDesc.BindFlags = D3D11_BIND_SHADER_RESOURCE;
texDesc.CPUAccessFlags = D3D11_CPU_ACCESS_WRITE;
texDesc.MiscFlags = 0;
// HALF is defined in xnamath.h, for storing 16-bit float.
std::vector<HALF> hmap(mHeightmap.size());
//current mHeightmap is all zero.
std::transform(mHeightmap.begin(), mHeightmap.end(), hmap.begin(), XMConvertFloatToHalf);
D3D11_SUBRESOURCE_DATA data;
data.pSysMem = &hmap[0];
data.SysMemPitch = m_terrainData.HeightmapWidth * sizeof(HALF);
data.SysMemSlicePitch = 0;
HR(device->CreateTexture2D(&texDesc, &data, &m_hmapTex));
D3D11_SHADER_RESOURCE_VIEW_DESC srvDesc;
srvDesc.Format = texDesc.Format;
srvDesc.ViewDimension = D3D11_SRV_DIMENSION_TEXTURE2D;
srvDesc.Texture2D.MostDetailedMip = 0;
srvDesc.Texture2D.MipLevels = -1;
HR(device->CreateShaderResourceView(m_hmapTex, &srvDesc, &mHeightMapSRV));
}
`HeightMap Texture modifying code
D3D11_MAPPED_SUBRESOURCE mappedData;
//m_hmapTex is ID3D11Texture2D*
HR(m_texMgr.m_context->Map(m_hmapTex, D3D11CalcSubresource(0, 0, 1), D3D11_MAP_WRITE_DISCARD, 0, &mappedData));
HALF* heightMapData = reinterpret_cast<HALF*>(mappedData.pData);
D3D11_TEXTURE2D_DESC heightmapDesc;
m_hmapTex->GetDesc(&heightmapDesc);
UINT width = heightmapDesc.Width;
for (int row = 0; row < width/4; ++row)
{
for (int col = 0; col < width/4; ++col)
{
idx = (row * width) + col;
heightMapData[idx] = static_cast<HALF>(XMConvertFloatToHalf(200));
}
}
m_texMgr.m_context->Unmap(m_hmapTex, D3D11CalcSubresource(0,0,1));
Please refer to the picture below
The lower right area renders the HeightMap texture.
I wanted to edit only 1/4 width and height, but that's all changed.
enter image description here
When the completed heightmap is applied, it works normally.
enter image description here

Answer 1

A texture does not always have the same width and height in memory as the definition suggests. Some textures strides (lines) are oversized. You have to use the Stride Size * Row to calculate the offset to write into.