how can I update dynamic vertex buffer fastly? - directx

I'm trying to make a simple 3D modeling tool.
there is some work to move a vertex( or vertices ) for transform the model.
I used dynamic vertex buffer because thought it needs much update.
but performance is too low in high polygon model even though I change just one vertex.
is there other methods? or did I wrong way?
here is my D3D11_BUFFER_DESC
Usage = D3D11_USAGE_DYNAMIC;
CPUAccessFlags = D3D11_CPU_ACCESS_WRITE;
BindFlags = D3D11_BIND_VERTEX_BUFFER;
ByteWidth = sizeof(ST_Vertex) * _nVertexCount
D3D11_SUBRESOURCE_DATA d3dBufferData;
d3dBufferData.pSysMem = pVerticesInfo;
hr = pd3dDevice->CreateBuffer(&descBuffer, &d3dBufferData, &_pVertexBuffer);
and my update funtion
D3D11_MAPPED_SUBRESOURCE d3dMappedResource;
pImmediateContext->Map(_pVertexBuffer, 0, D3D11_MAP_WRITE_DISCARD, 0, &d3dMappedResource);
ST_Vertex* pBuffer = (ST_Vertex*)d3dMappedResource.pData;
for (int i = 0; i < vIndice.size(); ++i)
{
pBuffer[vIndice[i]].xfPosition.x = pVerticesInfo[vIndice[i]].xfPosition.x;
pBuffer[vIndice[i]].xfPosition.y = pVerticesInfo[vIndice[i]].xfPosition.y;
pBuffer[vIndice[i]].xfPosition.z = pVerticesInfo[vIndice[i]].xfPosition.z;
}
pImmediateContext->Unmap(_pVertexBuffer, 0);

As mentioned in the previous answer, you are updating your whole buffer every time, which will be slow depending on model size.
The solution is indeed to implement partial updates, there are two possibilities for it, you want to update a single vertex, or you want to update
arbitrary indices (for example, you want to move N vertices in one go, in different locations, like vertex 1,20,23 for example.
The first solution is rather simple, first create your buffer with the following description :
Usage = D3D11_USAGE_DEFAULT;
CPUAccessFlags = 0;
BindFlags = D3D11_BIND_VERTEX_BUFFER;
ByteWidth = sizeof(ST_Vertex) * _nVertexCount
D3D11_SUBRESOURCE_DATA d3dBufferData;
d3dBufferData.pSysMem = pVerticesInfo;
hr = pd3dDevice->CreateBuffer(&descBuffer, &d3dBufferData, &_pVertexBuffer);
This makes sure your vertex buffer is gpu visible only.
Next create a second dynamic buffer which has the size of a single vertex (you do not need any bind flags in that case, as it will be used only for copies)
_pCopyVertexBuffer
Usage = D3D11_USAGE_DYNAMIC; //Staging works as well
CPUAccessFlags = D3D11_CPU_ACCESS_WRITE;
BindFlags = 0;
ByteWidth = sizeof(ST_Vertex);
D3D11_SUBRESOURCE_DATA d3dBufferData;
d3dBufferData.pSysMem = NULL;
hr = pd3dDevice->CreateBuffer(&descBuffer, &d3dBufferData, &_pCopyVertexBuffer);
when you move a vertex, copy the changed vertex in the copy buffer :
ST_Vertex changedVertex;
D3D11_MAPPED_SUBRESOURCE d3dMappedResource;
pImmediateContext->Map(_pVertexBuffer, 0, D3D11_MAP_WRITE_DISCARD, 0, &d3dMappedResource);
ST_Vertex* pBuffer = (ST_Vertex*)d3dMappedResource.pData;
pBuffer->xfPosition.x = changedVertex.xfPosition.x;
pBuffer->.xfPosition.y = changedVertex.xfPosition.y;
pBuffer->.xfPosition.z = changedVertex.xfPosition.z;
pImmediateContext->Unmap(_pVertexBuffer, 0);
Since you use D3D11_MAP_WRITE_DISCARD, make sure to write all attributes there (not only position).
Now once you done, you can use ID3D11DeviceContext::CopySubresourceRegion to only copy the modified vertex in the current location :
I assume that vertexID is the index of the modified vertex :
pd3DeviceContext->CopySubresourceRegion(_pVertexBuffer,
0, //must be 0
vertexID * sizeof(ST_Vertex), //location of the vertex in you gpu vertex buffer
0, //must be 0
0, //must be 0
_pCopyVertexBuffer,
0, //must be 0
NULL //in this case we copy the full content of _pCopyVertexBuffer, so we can set to null
);
Now if you want to update a list of vertices, things get more complicated and you have several options :
-First you apply this single vertex technique in a loop, this will work quite well if your changeset is small.
-If your changeset is very big (close to almost full vertex size, you can probably rewrite the whole buffer instead).
-An intermediate technique is to use compute shader to perform the updates (thats the one I normally use as its the most flexible version).
Posting all c++ binding code would be way too long, but here is the concept :
your vertex buffer must have BindFlags = D3D11_BIND_VERTEX_BUFFER | D3D11_BIND_UNORDERED_ACCESS; //this allows to write wioth compute
you need to create an ID3D11UnorderedAccessView for this buffer (so shader can write to it)
you need the following misc flags : D3D11_RESOURCE_MISC_BUFFER_ALLOW_RAW_VIEWS //this allows to write as RWByteAddressBuffer
you then create two dynamic structured buffers (I prefer those over byteaddress, but vertex buffer and structured is not allowed in dx11, so for the write one you need raw instead)
first structured buffer has a stride of ST_Vertex (this is your changeset)
second structured buffer has a stride of 4 (uint, these are the indices)
both structured buffers get an arbitrary element count (normally i use 1024 or 2048), so that will be the maximum amount of vertices you can update in a single pass.
both structured buffers you need an ID3D11ShaderResourceView (shader visible, read only)
Then update process is the following :
write modified vertices and locations in structured buffers (using map discard, if you have to copy less its ok)
attach both structured buffers for read
attach ID3D11UnorderedAccessView for write
set your compute shader
call dispatch
detach ID3D11UnorderedAccessView for write (this is VERY important)
This is a sample compute shader code (I assume you vertex is position only, for simplicity)
cbuffer cbUpdateCount : register(b0)
{
uint updateCount;
};
RWByteAddressBuffer RWVertexPositionBuffer : register(u0);
StructuredBuffer<float3> ModifiedVertexBuffer : register(t0);
StructuredBuffer<uint> ModifiedVertexIndicesBuffer : register(t0);
//this is the stride of your vertex buffer, since here we use float3 it is 12 bytes
#define WRITE_STRIDE 12
[numthreads(64, 1, 1)]
void CS( uint3 tid : SV_DispatchThreadID )
{
//make sure you do not go part element count, as here we runs 64 threads at a time
if (tid.x >= updateCount) { return; }
uint readIndex = tid.x;
uint writeIndex = ModifiedVertexIndicesBuffer[readIndex];
float3 vertex = ModifiedVertexBuffer[readIndex];
//byte address buffers do not understand float, asuint is a binary cast.
RWVertexPositionBuffer.Store3(writeIndex * WRITE_STRIDE, asuint(vertex));
}

For the purposes of this question I'm going to assume you already have a mechanism for selecting a vertex from a list of vertices based upon ray casting or some other picking method and a mechanism for creating a displacement vector detailing how the vertex was moved in model space.
The method you have for updating the buffer is sufficient for anything less than a few hundred vertices, but on large scale models it becomes extremely slow. This is because you're updating everything, rather than the individual vertices you modified.
To fix this, you should only update the vertices you have changed, and to do that you need to create a change set.
In concept, a change set is nothing more than a set of changes made to the data - a list of the vertices that need to be updated. Since we already know which vertices were modified (otherwise we couldn't have manipulated them), we can map in the GPU buffer, go to that vertex specifically, and copy just those vertices into the GPU buffer.
In your vertex modification method, record the index of the vertex that was modified by the user:
//Modify the vertex coordinates based on mouse displacement
pVerticesInfo[SelectedVertexIndex].xfPosition.x += DisplacementVector.x;
pVerticesInfo[SelectedVertexIndex].xfPosition.y += DisplacementVector.y;
pVerticesInfo[SelectedVertexIndex].xfPosition.z += DisplacementVector.z;
//Add the changed vertex to the list of changes.
changedVertices.add(SelectedVertexIndex);
//And update the GPU buffer
UpdateD3DBuffer();
In UpdateD3DBuffer(), do the following:
D3D11_MAPPED_SUBRESOURCE d3dMappedResource;
pImmediateContext->Map(_pVertexBuffer, 0, D3D11_MAP_WRITE, 0, &d3dMappedResource);
ST_Vertex* pBuffer = (ST_Vertex*)d3dMappedResource.pData;
for (int i = 0; i < changedVertices.size(); ++i)
{
pBuffer[changedVertices[i]].xfPosition.x = pVerticesInfo[changedVertices[i]].xfPosition.x;
pBuffer[changedVertices[i]].xfPosition.y = pVerticesInfo[changedVertices[i]].xfPosition.y;
pBuffer[changedVertices[i]].xfPosition.z = pVerticesInfo[changedVertices[i]].xfPosition.z;
}
pImmediateContext->Unmap(_pVertexBuffer, 0);
changedVertices.clear();
This has the effect of only updating the vertices that have changed, rather than all vertices in the model.
This also allows for some more complex manipulations. You can select multiple vertices and move them all as a group, select a whole face and move all the connected vertices, or move entire regions of the model relatively easily, assuming your picking method is capable of handling this.
In addition, if you record the change sets with enough information (the affected vertices and the displacement index), you can fairly easily implement an undo function by simply reversing the displacement vector and reapplying the selected change set.

Related

(DX12 Shadow Mapping) Depth buffer is always filled with 1

I'm really new to graphics programming in general, so please bear with me. I am trying to add shadow mapping from a distant light (orthogonal projection) into my scene, but when I follow the (very incomplete) steps from Frank Luna's DX12 book I find that my SRV for the shadow map is just filled with depths of 1.
If it helps, here is my SRV definition:
D3D12_TEX2D_SRV texDesc = {
0,
-1,
0,
0.0f
};
D3D12_SHADER_RESOURCE_VIEW_DESC srvDesc = {
DXGI_FORMAT_R32_TYPELESS,
D3D12_SRV_DIMENSION_TEXTURE2D,
D3D12_DEFAULT_SHADER_4_COMPONENT_MAPPING,
};
srvDesc.Texture2D = texDesc;
m_device->CreateShaderResourceView(m_lightDepthTexture.Get(),&srvDesc, m_cbvHeap->GetCPUDescriptorHandleForHeapStart());
and here are my DSV heap and descriptor definitions:
D3D12_DESCRIPTOR_HEAP_DESC dsvHeapDesc = {};
dsvHeapDesc.NumDescriptors = 2;
dsvHeapDesc.Type = D3D12_DESCRIPTOR_HEAP_TYPE_DSV;
dsvHeapDesc.Flags = D3D12_DESCRIPTOR_HEAP_FLAG_NONE;
ThrowIfFailed(m_device->CreateDescriptorHeap(&dsvHeapDesc, IID_PPV_ARGS(&m_dsvHeap)));
D3D12_DEPTH_STENCIL_VIEW_DESC depthStencilDesc = {};
depthStencilDesc.Format = DXGI_FORMAT_D32_FLOAT;
depthStencilDesc.ViewDimension = D3D12_DSV_DIMENSION_TEXTURE2D;
depthStencilDesc.Flags = D3D12_DSV_FLAG_NONE;
CD3DX12_HEAP_PROPERTIES heapProps = CD3DX12_HEAP_PROPERTIES(D3D12_HEAP_TYPE_DEFAULT);
CD3DX12_RESOURCE_DESC resourceDesc = CD3DX12_RESOURCE_DESC::Tex2D(DXGI_FORMAT_R32_TYPELESS, m_width, m_height, 1, 0, 1, 0, D3D12_RESOURCE_FLAG_ALLOW_DEPTH_STENCIL);
D3D12_CLEAR_VALUE depthOptimizedClearValue = {};
depthOptimizedClearValue.Format = DXGI_FORMAT_D32_FLOAT;
depthOptimizedClearValue.DepthStencil.Depth = 1.0f;
depthOptimizedClearValue.DepthStencil.Stencil = 0;
ThrowIfFailed(m_device->CreateCommittedResource(
&heapProps,
D3D12_HEAP_FLAG_NONE,
&resourceDesc,
D3D12_RESOURCE_STATE_DEPTH_WRITE,
&depthOptimizedClearValue,
IID_PPV_ARGS(&m_dsvBuffer)
));
D3D12_RESOURCE_DESC texDesc;
ZeroMemory(&texDesc, sizeof(D3D12_RESOURCE_DESC));
texDesc.Dimension = D3D12_RESOURCE_DIMENSION_TEXTURE2D;
texDesc.Alignment = 0;
texDesc.Width = m_width;
texDesc.Height = m_height;
texDesc.DepthOrArraySize = 1;
texDesc.MipLevels = 1;
texDesc.Format = DXGI_FORMAT_R32_TYPELESS;
texDesc.SampleDesc.Count = 1;
texDesc.SampleDesc.Quality = 0;
texDesc.Layout = D3D12_TEXTURE_LAYOUT_UNKNOWN;
texDesc.Flags = D3D12_RESOURCE_FLAG_ALLOW_DEPTH_STENCIL;
ThrowIfFailed(m_device->CreateCommittedResource(
&heapProps,
D3D12_HEAP_FLAG_NONE,
&texDesc,
D3D12_RESOURCE_STATE_GENERIC_READ,
&depthOptimizedClearValue,
IID_PPV_ARGS(&m_lightDepthTexture)
));
CD3DX12_CPU_DESCRIPTOR_HANDLE dsv(m_dsvHeap->GetCPUDescriptorHandleForHeapStart());
m_device->CreateDepthStencilView(m_dsvBuffer.Get(), &depthStencilDesc, dsv);
dsv.Offset(1, m_device->GetDescriptorHandleIncrementSize(D3D12_DESCRIPTOR_HEAP_TYPE_DSV));
m_device->CreateDepthStencilView(m_lightDepthTexture.Get(), &depthStencilDesc, dsv);
I then created a basic vertex shader that just transforms the vertices with my map (from Frank Luna's book, page 648,650). Since I bound the m_lightDepthTexture to D3D12GraphicsCommandList::OMSetRenderTargets, I assumed that the depth values would be written onto m_lightDepthTexture. But simply sampling this texture in my main pass proves that the values are actually 1.0f. So nothing actually happened on my shadow pass!
I really have no idea what to ask, but if anyone has a sample DX12 shadow map I could see (Google comes up with DX11 or less, or much too complicated samples), or if there's a good source to learn about this, please let me know!
EDIT: I should say that I changed the format from DXGI_FORMAT_D24_UNORM_S8_UINT, as I think the extra 8 bits for stencil is irrelevant to my case. I changed back to the book format and nothing changed, so I think this format should be fine.
If you remove the unecessary return ret; from your shadow vertex shader, the problem then seems to be in winding order of vertices of your sphere. You can easily verify this by setting cull mode to D3D12_CULL_MODE_NONE for your shadow PSO.
You can easily correct your sphere winding order by switching order of any two vertices of every triangle, so wherever you have p1,p2,p3 you just write it for example as p1,p3,p2.
You will also need to check your matrix multiplication order in your vertex shaders, I didn't checked it in detail but it's inconsistent and I believe the cause why the sphere will appear black when you fix the above issue. You also seem to be missing division by w for your light coords in lighting vertex shader.

Stop computing when Metal kernel output buffer is full?

I have a metal compute kernel that takes input points from a buffer particles, and populates a new buffer particlesOut. My compute kernel is defined as:
kernel void compute(device DrawingPoint *particles [[buffer(0)]],
device Particle *particlesOut [[buffer(1)]],
constant ComputeParameters *params [[buffer(2)]],
device atomic_int &counter [[buffer(3)]],
uint id [[thread_position_in_grid]]) {
This works fine, so long as the output buffer has room for the number of records populated.
So, for instance, if the input buffer has 10,000 records, and for each of those records I create 10 output records, and the output buffer has a length of 100,000, then all is fine. In other words, if the number of output records is fixed and is large enough, all is fine.
But for some input records, I would like a random number of output records to be populated. For instance, some I would like to populate 5, and another I would like to create 200 (and any number in-between).
I am using an atomic_int for the output record's position in the buffer. Again, this works if I have a fixed number of records populated per input record.
I am populating the output buffer like this:
//Output buffer is 10 times the size of the input buffer
for (int i = 0; i < 10; i++) {
int counterValue = atomic_fetch_add_explicit(&counter, 1, memory_order_relaxed);
...
particlesOut[counterValue].position = finalPoint;
}
This works fine.
If I try to make it work on a variable number instead of the fixed value, the buffer is way under populated (instead of getting say 100,000 particles populated, maybe only 10,000 are populated).
For example:
int numberOfOutputPoints = someRandomValueBetweenFiveAndTwoHundred();
for (int i = 0; i < numberOfOutputPoints; i++) {
int counterValue = atomic_fetch_add_explicit(&counter, 1, memory_order_relaxed);
//particleCount is the size of the output buffer
if (counterValue > params->particleCount) {
return;
}
...
particlesOut[counterValue].position = finalPoint;
}
When I do that, only a small number of the particles in the output buffer are actually populated.
I looked at using different options for atomic_fetch_add_explicit, but only memory_order_relaxed will compile.
I tried using:
int counterValue = atomic_fetch_add(&counter, 1)
But, the compiler reports that there is no matching function. Other than having the buffer output large enough for every record to populate the maximum number of possible particles populated (e.g. 200 times 10,000), is there any way to make it dynamic?
In other words, I just want to stop populating the output buffer when it is full.

WebGL attempt to access out of range vertices in attribute 2 error

I know this question has been asked quite a bit, but none of the solutions really fit my case. I am looking to add a second type of object to the canvas with the code shown below. I know I didn't provide much but its a quick start. Just ask for more if you think you have a hunch. This code below is in my render function.
So far I have checked that
I have enough vertices in my points array
I have enough normal vectors in my normals array
I have enough texture coordinates in my texCoords array
There are no mismatches between the vectors added when creating my terrain and my propeller.
The terrain renders just fine with the texture, lighting and all but,I am unable to get the propeller to render. I get the error I listed above. I have added multiple objects to canvases before and never run into an error like this.
//----------------------------------------- Draw Terrain ------------------------------------
var i = 0;
for(var row=0-dimension; row<dimension; row+=3){
for(var col=0-dimension; col<dimension; col+=3, i++){
var mv = mult(viewer, mult(translate(row, -1, col), mult(scale[i],rot[i])));
gl.uniformMatrix4fv(modelViewLoc, false, flatten(mv));
gl.uniformMatrix3fv(normalLoc, false, flatten(normalMatrix(mv, true)));
gl.drawArrays( gl.TRIANGLES, 0, index);
}
}
//----------------------------------------- Draw Propeller ------------------------------------
mv = mult(viewer, mult( translate(-2.1, -2.9, -.2), scalem(4,5,5)));
gl.uniformMatrix4fv(modelViewLoc, false, flatten(mv));
gl.uniformMatrix3fv(normalLoc, false, flatten(normalMatrix(mv, true)));
gl.drawArrays( gl.TRIANGLES, propellerStart, points.length);
Is there any way i can use the "Attribute 2" in the error message to track down the variable giving me this issue?
Appreciate the help!
What part don't you understand? The error is clear, whatever buffer you have attached to attribute 2 is not big enough to handle the propellerStart, points.length draw request.
So first thing is figure out which attribute is attribute 2. Do this by printing out your attribute locations. Is your points, normals, or texcoords?
You should already be looking them up somewhere with gl.getAttribLocation so print out those values, find out which one is #2.
Then go look at the size of the buffer you attached to that attribute. To do that somewhere you would have called.
gl.bindBuffer(gl.ARRAY_BUFFER, someBuffer);
gl.vertexAttribPointer(locationForAttribute2, size, type, normalize, stride, offset);
So we know it's someBuffer from the above code. We also need to know size, type, stride, and offset
Somewhere else you filled that buffer with data using
gl.bindBuffer(gl.ARRAEY_BUFFER, someBuffer);
gl.bufferData(gl.ARRAY_BUFFER, someData, ...);
So you need to find the size of someData.
sizeOfBuffer = someData.length * someData.BYTES_PER_ELEMENT
Let's it's a 1000 element Float32Array so it someData.length is 1000 and someData.BYTES_PER_ELEMENT is 4 therefore sizeOfBuffer is 4000.
Using all of that you can now check if your buffer is too small. (note: we already know it's too small since the browser told us so but if you want know how to compute it yourself)
Let's say size is 3, type is gl.FLOAT, stride is 32, offset is 12 (note: I personally never use anything but stride = 0 and offset = 0)
Let's say points.length = 50
numPoints = points.length;
bytesPerElement = size * 4; // because a gl.FLOAT is 4 bytes
realStride = stride === 0 ? bytesPerElement : stride;
bytesNeeded = realStride * (numPoints - 1) + bytesPerElement;
bytesNeeded in this case is (64 * 49) + 12 = 3148
So now we know how many bytes are needed. Does are buffer have enough data? We'll when you called draw you passed in an offset propellerStart. Let's assume it's 900 and there's the offset in the attribute so.
bufferSizeNeeded = offset + propellerStart + bytesNeeded
so bufferSizeNeeded = 12 + 900 + 3148 which is 4060. Since 4060 is > sizeOfBuffer which was 4000 you're going to get the error you got.
In any case the point is really it's up to you to figure out which buffer is used by attribute #2, then go look at why your buffer is too small. Is your offset to drawArrays wrong? Is your stride too big? Is your offset wrong in vertexAttribPointer (it's in number of bytes not number of units). Do you put the wrong size (1,2,3,4). Do you mis-calculate the number of points?

Update directX texture

How can I solve following task: some app need to
use dozens dx9 terxtures (render them with dx3d)
and
update some of them (whole or in part).
I.e. sometimes (once per frame/second/minute) i need to write bytes (void *) in different formats (argb, bgra, rgb, 888, 565) to some sub-rect of existing texture.
In openGL solution is very simple - glTexImage2D. But here unfamiliar platform features completely confused me.
Interested in solution for both dx9 and dx11.
To update a texture, make sure the texture is created in D3DPOOL_MANAGED memory pool.
D3DXCreateTexture( device, size.x, size.y, numMipMaps,usage, textureFormat, D3DPOOL_MANAGED, &texture );
Then call LockRect to update the data
RECT rect = {x,y,z,w}; // the dimensions you want to lock
D3DLOCKED_RECT lockedRect = {0}; // "out" parameter from LockRect function below
texture->LockRect(0, &lockedRect, &rect, 0);
// copy the memory into lockedRect.pBits
// make sure you increment each row by "Pitch"
unsigned char* bits = ( unsigned char* )lockedRect.pBits;
for( int row = 0; row < numRows; row++ )
{
// copy one row of data into "bits", e.g. memcpy( bits, srcData, size )
...
// move to the next row
bits += lockedRect.Pitch;
}
// unlock when done
texture->UnlockRect(0);

View GPU Memory / View Texture2D memory space for debugging

I've got a question about a PixelShader I am trying to implement, and what I currently do (this is just for debugging, and trying to figure stuff out):
int3 loc;
loc.x = (int)(In.TextureUV.x * resolution_XY.x);
loc.y = (int)(In.TextureUV.x * resolution_XY.x);
loc.z = 0;
float4 r = g_txDiffuse.Load(loc);
return float4(r.x, r.y, r.z, 1);
The point is, this is always 0,0,0,1
The texture buffer is created:
D3D11_TEXTURE2D_DESC tDesc;
tDesc.Height = 480;
tDesc.Width = 640;
tDesc.Usage = D3D11_USAGE_DYNAMIC;
tDesc.MipLevels = 1;
tDesc.ArraySize = 1;
tDesc.SampleDesc.Count = 1;
tDesc.SampleDesc.Quality = 0;
tDesc.Format = DXGI_FORMAT_R8_UINT;
tDesc.CPUAccessFlags = D3D11_CPU_ACCESS_WRITE;
tDesc.BindFlags = D3D11_BIND_SHADER_RESOURCE;
tDesc.MiscFlags = 0;
V_RETURN(pd3dDevice->CreateTexture2D(&tDesc, NULL, &g_pCurrentImage));
I upload the texture (which should be a live display at the end) via:
D3D11_MAPPED_SUBRESOURCE resource;
pd3dImmediateContext->Map(g_pCurrentImage, 0, D3D11_MAP_WRITE_DISCARD, 0, &resource);
memcpy( resource.pData, g_Images.GetData(), g_Images.GetDataSize() );
pd3dImmediateContext->Unmap( g_pCurrentImage, 0 );
I've checked the resource.pData, the data in there is a valid 8bit monochrome image. I made sure the data coming from the camera is 8bit monochrome 640x480.
There's a few things I don't fully understand:
if I run the Map / memcpy / Unmap routine in every frame, the driver will ultimately crash, the system will be unresponsive. Is there a different way to update a complete texture every frame which should be done?
the texture I uploaded is 8bit, why is the Texture2D.load() a float4 return? Do I have to use a different method to access the texture data? I tried to .sample it, but that didn't work either. Would I have to use a int buffer or something instead?
is there a way to debug the GPU memory, to check if the memcpy worked in the first place?
The Map, memcpy, Unmap really ought not to crash unless2 you are trying to copy too much data into the texture. It would be interesting to know what "GetDataSize()" returns. Does it equal 307,200? If its more than that then there lies your problem.
Texture2D returns a float4 because thats what you've asked for. If you write float r = g_txDiffuse.Load( ... ). The 8-bits get extended to a normalised float as part of the load process. Are you sure, btw, that your calculation of "loc" is correct because as you have it now loc.x and loc.y will always be the same.
You can debug whats going on with DirectX using PIX. Its a great tool and I highly recommend you familiarise yourself with it.

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