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I am totally lost now. Have been trying to read the backbuffer inside a vertex shader for days with no luck whatsoever.
I'm trying to read the vertexes position from the backbuffer and it's neighboring pixels. (I'm trying to count how many black pixels are around a vertex, and if there are any color that vertex red in the pixel shader). I've created a separate ID3D11Texture2D and an SRV to go with the backBuffer. I copy the backbuffer into this SRV's resource. Bind the SRV using VSSetShaderResources but just can't seem to be able to read from it inside the vertex shader.
I will share some code here from the creation of these elements as well as include some RenderDoc screenshots that keep showing that the SRV is being bound to the VS stage and has the right texture associated with it but every Load or []operator or tex2dlod or SampleLevel(i bound a SamplerState too)
just keeps returning a single 1.0 value with the rest of the float4 never being returned, meaning i only get a float1 back. I will also include a renderdoc capture file if anyone wants to take a look.
This is a simple scene from tutorial 42 on the rastertek.com site, there is a ground plane with a cube and a sphere on it :
https://i.imgur.com/cbVC48E.gif
// Here is some code when creating the secondary texture and SRV that houses a //backBuffer
// Get the pointer to the back buffer.
result = m_swapChain->GetBuffer(0, __uuidof(ID3D11Texture2D), (LPVOID*)&backBufferPtr);
if(FAILED(result))
{
MessageBox((*(hwnd)), L"Get the pointer to the back buffer FAILED", L"Error", MB_OK);
return false;
}
// Create another texture2d that we will use to make an SRV out of, and this texture2d will be used to copy the backbuffer to so we can read it in a shader
D3D11_TEXTURE2D_DESC bbDesc;
backBufferPtr->GetDesc(&bbDesc);
bbDesc.MipLevels = 1;
bbDesc.ArraySize = 1;
bbDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
bbDesc.Usage = D3D11_USAGE_DEFAULT;
bbDesc.MiscFlags = 0;
bbDesc.BindFlags = D3D11_BIND_SHADER_RESOURCE;
result = m_device->CreateTexture2D(&bbDesc, NULL, &m_backBufferTx2D);
if (FAILED(result))
{
MessageBox((*(m_hwnd)), L"Create a Tx2D for backbuffer SRV FAILED", L"Error", MB_OK);
return false;
}
D3D11_SHADER_RESOURCE_VIEW_DESC descSRV;
ZeroMemory(&descSRV, sizeof(descSRV));
descSRV.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
descSRV.ViewDimension = D3D11_SRV_DIMENSION_TEXTURE2D;
descSRV.Texture2D.MipLevels = 1;
descSRV.Texture2D.MostDetailedMip = 0;
result = GetDevice()->CreateShaderResourceView(m_backBufferTx2D, &descSRV, &m_backBufferSRV);
if (FAILED(result))
{
MessageBox((*(m_hwnd)), L"Creating BackBuffer SRV FAILED.", L"Error", MB_OK);
return false;
}
// Create the render target view with the back buffer pointer.
result = m_device->CreateRenderTargetView(backBufferPtr, NULL, &m_renderTargetView);
First I render the scene in all white and then I copy that to the SRV and bind it for the next shader that's supposed to sample it. I'm expecting to get a float4(1.0, 1.0, 1.0, 1.0) value returned when i sample the backbuffer with the vertex's on screen position
https://i.imgur.com/N9CYg8c.png
as shown on the top left in the event browser, there were three drawindexed calls for rendering everything in white and then a CopyResource.
I've selected the next (fourth) DrawIndexed and on the right side outlined in red are the inputs for this next shader clearly showing that the backBuffer has been successfully bound to the vertex shader.
And now for the part that's giving me trouble
https://i.imgur.com/ENuXk0n.png
I'm gonna be debugging this top-left vertex as shown on the screenshot,
the vertex Shader has a
Texture2D prevBackBuffer: register(t0);
written at the top
https://i.imgur.com/8cihNsq.png
When trying to sample the left neighboring pixel
this line of code returns newCoord = float2(158, 220)
when entering these pixel values in the texture view i get this pixel
https://i.imgur.com/DT72Fl1.png
so the coordinates are ok so far, and as outlined i'm expecting to get a float4(0.0, 0.0, 0.0, 1,0) returned when i sample this pixel
(I'm trying to count how many black pixels are around a vertex, and if there are any color that vertex red in the pixel shader)
AND YET, when i sample that pixel right after altering the pixel coordinates since load counts pixels from bottom left so i need
newCoord = float2(158, 379), i get this
https://i.imgur.com/8SuwOzz.png
why is this, even if it's out of range, load should return all zeros, since I'm not sure about the whole load counts from bottom left thing I tried sampling using the top left coordinates (158, 220) but end up getting 0.0, ?, ?, ?
I'm completely stumped and have no idea what to try next. I've tried using a sample state :
// Create a clamp texture sampler state description.
samplerDesc.Filter = D3D11_FILTER_MIN_MAG_MIP_LINEAR;
samplerDesc.AddressU = D3D11_TEXTURE_ADDRESS_CLAMP;
samplerDesc.AddressV = D3D11_TEXTURE_ADDRESS_CLAMP;
samplerDesc.AddressW = D3D11_TEXTURE_ADDRESS_CLAMP;
samplerDesc.MipLODBias = 0.0f;
samplerDesc.MaxAnisotropy = 1;
samplerDesc.ComparisonFunc = D3D11_COMPARISON_ALWAYS;
samplerDesc.BorderColor[0] = 0;
samplerDesc.BorderColor[1] = 0;
samplerDesc.BorderColor[2] = 0;
samplerDesc.BorderColor[3] = 0;
samplerDesc.MinLOD = 0;
samplerDesc.MaxLOD = D3D11_FLOAT32_MAX;
// Create the texture sampler state.
result = device->CreateSamplerState(&samplerDesc, &m_sampleStateClamp);
but still never get a proper float4 back when reading the texture.
Any ideas, suggestions, I'll take anything at this point.
Oh and here's a RenderDoc file of the frame i was examining :
http://www.mediafire.com/file/1bfiqdpjkau4l0n/my_capture.rdc/file
So from my experience, reading from the back buffer is not really an operation that you want to be doing in the first place. If you have to do any operation on the rendered scene, the best way to do that is to render the scene to an intermediate texture, perform the operation on that texture, then render the final scene to the back buffer. This is generally how things like dynamic shadows are done - the scene is rendered from the perspective of the light, and the resulting buffer is interpreted to get a shadow value that is then applied to the final scene (this is also why dynamic light sources are limited in commercial game engines - they're rather expensive to use).
A similar idea can be applied here. First, render the whole scene to an intermediate texture, bound as a render target view (where the pixel format is specified by you, the programmer). Next, rebind that intermediate texture as a shader resource view, and render the scene again, using the edge detection shader and the real back buffer (where the pixel format is defined by the hardware).
This, fundamentally, is what I believe the issue is - a back buffer is a device dependent resource, and its format can change depending on the hardware. Therefore, using it from a shader is not safe, as you don't always know what the format will be. A device independent resource, on the other hand, will always have the same format, and you can safely use it however you like from a shader.
I wasn't able to get sampling an SRV in the vertex shader to work
but what i was able to get working
is using a backBuffer.SampleLevel inside a compute shader
I also had to change the sampler to something like this :
D3D11_SAMPLER_DESC samplerDesc;
samplerDesc.Filter = D3D11_FILTER_MIN_MAG_MIP_POINT;
samplerDesc.AddressU = D3D11_TEXTURE_ADDRESS_BORDER;
samplerDesc.AddressV = D3D11_TEXTURE_ADDRESS_BORDER;
samplerDesc.AddressW = D3D11_TEXTURE_ADDRESS_BORDER;
samplerDesc.MipLODBias = 0.0f;
samplerDesc.MaxAnisotropy = 1;
samplerDesc.ComparisonFunc = D3D11_COMPARISON_ALWAYS;
samplerDesc.BorderColor[0] = 0.5f;
samplerDesc.BorderColor[1] = 0.5f;
samplerDesc.BorderColor[2] = 0.5f;
samplerDesc.BorderColor[3] = 0.5f;
samplerDesc.MinLOD = 0;
samplerDesc.MaxLOD = 0;
I am trying to render a texture that gets passed through a pixel shader.
Currently my shader is as follows:
float4 EffectProcess( float2 Tex : TEXCOORD0 ) : COLOR0
{
return float4(1,0,0,1);
}
technique MyTechnique
{
pass p0
{
VertexShader = null;
PixelShader = compile ps_2_0 EffectProcess();
}
}
As you can see, it is a very basic shader that makes that forces the pixels to be red.
UINT uiPasses = 0;
res= g_lpEffect->Begin(&uiPasses, 0);
for (UINT uiPass = 0; uiPass < uiPasses; uiPass++)
{
res = g_lpEffect->BeginPass(uiPass);
res = sprite->Begin(D3DXSPRITE_SORT_TEXTURE);
res = sprite->Draw(tex, NULL, 0x0, 0x0, 0xFFFFFFFF);
res = sprite->End();
res = g_lpEffect->EndPass();
}
res = g_lpEffect->End();
And I am drawing the texture using the shader like so. I am not sure this is the correct way to do it though and have found very little resources on the subject.
The shader is being created correctly and the texture aswell, all calls return a hresult of S_OK, yet when I run the code, the texture shows perfectly, without being overwritten by red.
Both sprite and effects by default store initial pipeline state and set up their own when Begin is called and then restore it when End is called. So I suspect that sprite->Begin(D3DXSPRITE_SORT_TEXTURE); will disable effect processing and your pixel shader is never called. You may try to pass something like D3DXSPRITE_DONOTMODIFY_RENDERSTATE into Begin to prevent it from modifying pipeline state, though this may break sprite rendering. It would be better to get rid of sprite altogether and write your own sprite shader (both vertex and pixel) because fixed pipeline rendering is mostly deprecated these days.
(Edit) I made working geometry picking with framebuffer. My goal is draw huge scene in one draw call, but I need to draw to multisample color texture attachment (GL_COLOR_ATTACHMENT0) and draw to (eddited) non-multisample picking texture attachment (GL_COLOR_ATTACHMENT1). The problem is if I use multisample texture to pick, picking is corrupted because of multi-sampling.
I write geometry ID to fragment shader like this:
//...
// Given geometry id
uniform int in_object_id;
// Drawed to screen (GL_COLOR_ATTACHMENT0)
out vec4 out_frag_color0;
// Drawed to pick texture (GL_COLOR_ATTACHMENT1)
out vec4 out_frag_color1;
// ...
void main() {
out_frag_color0 = ...; // Calculating lighting and other stuff
//...
const int max_byte1 = 256;
const int max_byte2 = 65536;
const float fmax_byte = 255.0;
int a1 = in_object_id % max_byte1;
int a2 = (in_object_id / max_byte1) % max_byte1;
int a3 = (in_object_id / max_byte2) % max_byte1;
//out_frag_color0 = vec4(a3 / fmax_byte, a2 / fmax_byte, a1 / fmax_byte, 1);
out_frag_color1 = vec4(a3 / fmax_byte, a2 / fmax_byte, a1 / fmax_byte, 1);
}
(Point of that code is use RGB space for store geometry ID which is then read back a using for changing color of cube)
This happens when I move cursor by one pixel to left:
Because of alpha value of cube pixel:
Without multisample is works well. But multisampling multiplies my output color and geometry id is then corrupted, so it selects random cube with multiplied value.
(Edit) I can't attach one multisample texture target to color0 and non-multisample texture target to color1, it's not supported. How can I do this in one draw call?
Multisampling is not my friend I am not sure If I understand it well (whole framebuffering). Anyway, this way to pick geometries looks horrible for me (I meant calculating ID to color). Am I doing it well? How can I solve multisample problem? Is there better way?
PS: Sorry for low english. :)
Thanks.
You can't do multisampled and non-multisampled rendering in a single draw call.
As you already found, using two color targets in an FBO, with only one of them being multisampled, is not supported. From the "Framebuffer Completeness" section in the spec:
The value of RENDERBUFFER_SAMPLES is the same for all attached renderbuffers; the value of TEXTURE_SAMPLES is the same for all attached textures; and, if the attached images are a mix of renderbuffers and textures, the value of RENDERBUFFER_SAMPLES matches the value of TEXTURE_SAMPLES.
You also can't render to multiple framebuffers at the same time. There is always one single current framebuffer.
The only reasonable option I can think of is to do picking in a separate pass. Then you can easily switch the framebuffer/attachment to a non-multisampled renderbuffer, and avoid all these issues.
Using a separate pass for picking seems cleaner to me anyway. This also allows you to use a specialized shader for each case, instead of always producing two outputs even if one of them is mostly unused.
I think it is posible...
You have to set the picking texture to multisampled and after rendering the scene, you can render 2 triangles over the screen and inside another fragmentshader you can readout each sample... to do that you have to use the GLSL command:
texelFetch(sampler, pixelposition/*[0-texturesize]*/, /*important*/layernumber);
Then you can render it into a single-sampled texture and read the color via glReadPixel.
I haven't tested it now, but I think it works
I have a fairly simple DirectX 11 framework setup that I want to use for various 2D simulations. I am currently trying to implement the 2D Wave Equation on the GPU. It requires I keep the grid state of the simulation at 2 previous timesteps in order to compute the new one.
How I went about it was this - I have a class called FrameBuffer, which has the following public methods:
bool Initialize(D3DGraphicsObject* graphicsObject, int width, int height);
void BeginRender(float clearRed, float clearGreen, float clearBlue, float clearAlpha) const;
void EndRender() const;
// Return a pointer to the underlying texture resource
const ID3D11ShaderResourceView* GetTextureResource() const;
In my main draw loop I have an array of 3 of these buffers. Every loop I use the textures from the previous 2 buffers as inputs to the next frame buffer and I also draw any user input to change the simulation state. I then draw the result.
int nextStep = simStep+1;
if (nextStep > 2)
nextStep = 0;
mFrameArray[nextStep]->BeginRender(0.0f,0.0f,0.0f,1.0f);
{
mGraphicsObj->SetZBufferState(false);
mQuad->GetRenderer()->RenderBuffers(d3dGraphicsObj->GetDeviceContext());
ID3D11ShaderResourceView* texArray[2] = { mFrameArray[simStep]->GetTextureResource(),
mFrameArray[prevStep]->GetTextureResource() };
result = mWaveShader->Render(d3dGraphicsObj, mQuad->GetRenderer()->GetIndexCount(), texArray);
if (!result)
return false;
// perform any extra input
I_InputSystem *inputSystem = ServiceProvider::Instance().GetInputSystem();
if (inputSystem->IsMouseLeftDown()) {
int x,y;
inputSystem->GetMousePos(x,y);
int width,height;
mGraphicsObj->GetScreenDimensions(width,height);
float xPos = MapValue((float)x,0.0f,(float)width,-1.0f,1.0f);
float yPos = MapValue((float)y,0.0f,(float)height,-1.0f,1.0f);
mColorQuad->mTransform.position = Vector3f(xPos,-yPos,0);
result = mColorQuad->Render(&viewMatrix,&orthoMatrix);
if (!result)
return false;
}
mGraphicsObj->SetZBufferState(true);
}
mFrameArray[nextStep]->EndRender();
prevStep = simStep;
simStep = nextStep;
ID3D11ShaderResourceView* currTexture = mFrameArray[nextStep]->GetTextureResource();
// Render texture to screen
mGraphicsObj->SetZBufferState(false);
mQuad->SetTexture(currTexture);
result = mQuad->Render(&viewMatrix,&orthoMatrix);
if (!result)
return false;
mGraphicsObj->SetZBufferState(true);
The problem is nothing is happening. Whatever I draw appears on the screen(I draw using a small quad) but no part of the simulation is actually ran. I can provide the shader code if required, but I am certain it works since I've implemented this before on the CPU using the same algorithm. I'm just not certain how well D3D render targets work and if I'm just drawing wrong every frame.
EDIT 1:
Here is the code for the begin and end render functions of the frame buffers:
void D3DFrameBuffer::BeginRender(float clearRed, float clearGreen, float clearBlue, float clearAlpha) const {
ID3D11DeviceContext *context = pD3dGraphicsObject->GetDeviceContext();
context->OMSetRenderTargets(1, &(mRenderTargetView._Myptr), pD3dGraphicsObject->GetDepthStencilView());
float color[4];
// Setup the color to clear the buffer to.
color[0] = clearRed;
color[1] = clearGreen;
color[2] = clearBlue;
color[3] = clearAlpha;
// Clear the back buffer.
context->ClearRenderTargetView(mRenderTargetView.get(), color);
// Clear the depth buffer.
context->ClearDepthStencilView(pD3dGraphicsObject->GetDepthStencilView(), D3D11_CLEAR_DEPTH, 1.0f, 0);
void D3DFrameBuffer::EndRender() const {
pD3dGraphicsObject->SetBackBufferRenderTarget();
}
Edit 2 Ok, I after I set up the DirectX debug layer I saw that I was using an SRV as a render target while it was still bound to the Pixel stage in out of the shaders. I fixed that by setting shader resources to NULL after I render with the wave shader, but the problem still persists - nothing actually gets ran or updated. I took the render target code from here and slightly modified it, if its any help: http://rastertek.com/dx11tut22.html
Okay, as I understand correct you need a multipass-rendering to texture.
Basiacally you do it like I've described here: link
You creating SRVs with both D3D11_BIND_SHADER_RESOURCE and D3D11_BIND_RENDER_TARGET bind flags.
You ctreating render targets from textures
You set first texture as input (*SetShaderResources()) and second texture as output (OMSetRenderTargets())
You Draw()*
then you bind second texture as input, and third as output
Draw()*
etc.
Additional advices:
If your target GPU capable to write to UAVs from non-compute shaders, you can use it. It is much more simple and less error prone.
If your target GPU suitable, consider using compute shader. It is a pleasure.
Don't forget to enable DirectX debug layer. Sometimes we make obvious errors and debug output can point to them.
Use graphics debugger to review your textures after each draw call.
Edit 1:
As I see, you call BeginRender and OMSetRenderTargets only once, so, all rendering goes into mRenderTargetView. But what you need is to interleave:
SetSRV(texture1);
SetRT(texture2);
Draw();
SetSRV(texture2);
SetRT(texture3);
Draw();
SetSRV(texture3);
SetRT(backBuffer);
Draw();
Also, we don't know what is mRenderTargetView yet.
so, before
result = mColorQuad->Render(&viewMatrix,&orthoMatrix);
somewhere must be OMSetRenderTargets .
Probably, it s better to review your Begin()/End() design, to make resource binding more clearly visible.
Happy coding! =)
In my OpenGL program I have two shaders. One renders with textures, and the other renders just solid colors. After compiling and linking a shader, I enable a texture coordinate vertex attribute array depending on weather or not the shader contains the attribute.
//This code is called after the shaders are compiled.
//Get the handles
textureU = glGetUniformLocation(program,"texture");
tintU = glGetUniformLocation(program,"tint");
viewMatrixU = glGetUniformLocation(program,"viewMatrix");
transformMatrixU = glGetUniformLocation(program,"transformMatrix");
positionA = glGetAttribLocation(program,"position");
texcoordA = glGetAttribLocation(program,"texcoord");
//Detect if this shader can handle textures
if(texcoordA < 0 || textureU < 0) hasTexture = false;
else hasTexture = true;
//Enable Attributes
glEnableVertexAttribArray(positionA);
if(hasTexture) glEnableVertexAttribArray(texcoordA);
If I am rendering an item that is textured, each element in verts consists of 5 values (x,y,z,tx,ty), but if the item isn't textures, each element in verts contains only 3 values (x,y,z).
Here is the problem: When the first item rendered in the GL context does not have a texture, glDrawElements segfaults! However, if the first item rendered does have a texture, it works fine, and any untextured items after the textured one work fine (that is, until a new context is created).
This chunk of code renders an item
glBindBuffer(GL_ARRAY_BUFFER,engine->vertBuffer);
glBufferData(GL_ARRAY_BUFFER,sizeof(GLfloat)*item->verts.size(),&item->verts[0],GL_DYNAMIC_DRAW);
item->shader->SetShader();
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER,engine->elementBuffer);
glBufferData(GL_ELEMENT_ARRAY_BUFFER,sizeof(GLuint) * item->indicies.size(),&item->indicies[0],GL_DYNAMIC_DRAW);
if(item->usingTexture)
item->shader->SetTexture(item->texture->handle);
glUniformMatrix4fv(item->shader->transformMatrixU,1,GL_TRUE,&item->matrix.contents[0]);
glUniformMatrix4fv(item->shader->viewMatrixU,1,GL_TRUE,&item->batch->matrix.contents[0]);
glUniform4f(item->shader->tintU,item->color.x,item->color.y,item->color.z,item->color.w);
glDrawElements(GL_TRIANGLES,item->indicies.size(),GL_UNSIGNED_INT,0); //segfault
Here is the function seen above that sets the shader.
glUseProgram(program); currentShader = program;
GLsizei stride = 12;
if(hasTexture) stride = 20;
glVertexAttribPointer(positionA,3,GL_FLOAT,GL_FALSE,stride,0);
if(hasTexture)
glVertexAttribPointer(texcoordA,2,GL_FLOAT,GL_FALSE,stride,(void*)12);
As far as I know, this problem is not apparent on Intel Integrated Graphics, which seem to be quite lenient.
Edit: If it is useful to know, I am using GLFW and GLEW.
Try adding corresponding glDisableVertexAttribArray()s after your draw call:
glEnableVertexAttribArray(positionA);
if(hasTexture) glEnableVertexAttribArray(texcoordA);
// draw
glDisableVertexAttribArray(positionA);
if(hasTexture) glDisableVertexAttribArray(texcoordA);
The problem is that I enabled the vertex attribute arrays after compiling my shader. This is not where I should have been enabling them.
I enabled the texcoord attribute when compiling the shader, but since the first item didn't use it, glDrawElements would segfault.
I fixed this by enabling the attribute when setting the shader.