DX11 [SharpDX] Understanding DX11 blend states

This topic is 1873 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

Recommended Posts

In dx9, the blend state was fairly simple. In dx11, it's a lot more complicated and I'm having trouble understanding how I need to have it set. I have a small app that is supposed to draw several instances of tessellated bezier triangles, and even though I have the pixel shader set to just paint one color, I'm not seeing that color on my screen at all. I've looked at my app with PIX (I use VS 2012 Express so it's my only debugging option for now.) and my vertex buffers seem to be doing what they are supposed to.

Right now I'm wondering about the blend state because I don't fully understand it. Here is how I have it set in my render method:

            RenderTargetBlendDescription rendBlendDesc = new RenderTargetBlendDescription();
rendBlendDesc.SourceAlphaBlend = BlendOption.One;
rendBlendDesc.DestinationAlphaBlend = BlendOption.Zero;
rendBlendDesc.SourceBlend = BlendOption.One;
rendBlendDesc.DestinationBlend = BlendOption.Zero;

BlendStateDescription blendDesc = new BlendStateDescription();
blendDesc.AlphaToCoverageEnable = false;
blendDesc.IndependentBlendEnable = false;
blendDesc.RenderTarget[0] = rendBlendDesc;

BlendState blendState = new BlendState(Game.GraphicsDevice, blendDesc);
Game.GraphicsDevice.ImmediateContext.OutputMerger.SetBlendState(blendState);



Do you see anything here that would prevent drawing from being visible?

Share on other sites

Your blend state will result in the pixel shader value being written to the render target(s), and completely overwriting any existing contents of the render target. This is pretty standard for rendering without any blending. If you're not seeing your primitives, then the problem is probably somewhere else.

I would recommend enabling device debug messages if you haven't already, and checking for any warning or messages. Pass the "Debug" flag when creating your device to specify that you want messages, and then enable native debugging for your project. You should then get messages in your debugger output window. If you're using an express version of VS or you don't want to turn on native debugging, you can use a program like DebugView to view the native debugger output stream.

Share on other sites

I used to use DebugView for my dx9 stuff and it was very useful. This time though I'm not seeing any warnings in the DebugView window even though I have created my device with the debug option. Does dx11 have a messaging level like dx9 had? I haven't used DebugView for a couple of years, and I can't remember all the steps necessary to capture messages from my app.

Share on other sites

Do you see the triangles without this blending turned on?
If not, then 2 quick tips: forgot to transpose the viewprojection matrix, or forgot to set some constant buffer to the proper shaders. At least those are my main 2 sources of pain nowadays.

You can turn on dx debug in sdk->utilities->Directx control panel, if you haven't already. I got some usefull info about not setting the proper patch type for my hull shader, which made the driver reset, so it can be usefull,but not a magic bullet.

Share on other sites

I used to use DebugView for my dx9 stuff and it was very useful. This time though I'm not seeing any warnings in the DebugView window even though I have created my device with the debug option. Does dx11 have a messaging level like dx9 had? I haven't used DebugView for a couple of years, and I can't remember all the steps necessary to capture messages from my app.

There's not really a "message level" anymore. There's functionality to filter out certain warnings/errors using the ID3D11InfoQueue interface, but by default you get all possible warnings and errors.

If you're not getting any messages, then it's possible you're not causing any errors or warnings. To find out for sure, you could try to deliberately cause an error by passing an incorrect parameter to a function, or something like that.

Share on other sites

You will be able to see D3D11 messages directly from the output window if you check "Enable native code debugging" in the Project Properties/Debug tab (you need to use the debugger to see the messages) otherwise DebugView is still an option.

Share on other sites

Thanks everyone, of course things are made worse by the fact that I have to stick with express version of VS for now. Very hard to learn dx11 with express.

Share on other sites

You will be able to see D3D11 messages directly from the output window if you check "Enable native code debugging" in the Project Properties/Debug tab (you need to use the debugger to see the messages) otherwise DebugView is still an option.

Oh my gosh! This is working with express! Somebody told me it wouldn't. Now I have about 100 pages of warnings to examine. Thanks!

Share on other sites

I'm not sure how easy it would be to interface with that API from C# though, as the SharpDX implementation looks incomplete.

It is not incomplete, the class is marked as "partial" so the other part of the code is generated at built time by the DirectX C++ to C# code generator used in SharpDX.

Edit: Though there are here some NotImplementedException for GetStorageFilter/GetRetrievalFilter, will have to double check :D

Edited by xoofx

• 16
• 9
• 13
• 41
• 15
• Similar Content

• By chiffre
Introduction:
In general my questions pertain to the differences between floating- and fixed-point data. Additionally I would like to understand when it can be advantageous to prefer fixed-point representation over floating-point representation in the context of vertex data and how the hardware deals with the different data-types. I believe I should be able to reduce the amount of data (bytes) necessary per vertex by choosing the most opportune representations for my vertex attributes. Thanks ahead of time if you, the reader, are considering the effort of reading this and helping me.
I found an old topic that shows this is possible in principal, but I am not sure I understand what the pitfalls are when using fixed-point representation and whether there are any hardware-based performance advantages/disadvantages.
(TLDR at bottom)
The Actual Post:
To my understanding HLSL/D3D11 offers not just the traditional floating point model in half-,single-, and double-precision, but also the fixed-point model in form of signed/unsigned normalized integers in 8-,10-,16-,24-, and 32-bit variants. Both models offer a finite sequence of "grid-points". The obvious difference between the two models is that the fixed-point model offers a constant spacing between values in the normalized range of [0,1] or [-1,1], while the floating point model allows for smaller "deltas" as you get closer to 0, and larger "deltas" the further you are away from 0.
To add some context, let me define a struct as an example:
struct VertexData { float[3] position; //3x32-bits float[2] texCoord; //2x32-bits float[3] normals; //3x32-bits } //Total of 32 bytes Every vertex gets a position, a coordinate on my texture, and a normal to do some light calculations. In this case we have 8x32=256bits per vertex. Since the texture coordinates lie in the interval [0,1] and the normal vector components are in the interval [-1,1] it would seem useful to use normalized representation as suggested in the topic linked at the top of the post. The texture coordinates might as well be represented in a fixed-point model, because it seems most useful to be able to sample the texture in a uniform manner, as the pixels don't get any "denser" as we get closer to 0. In other words the "delta" does not need to become any smaller as the texture coordinates approach (0,0). A similar argument can be made for the normal-vector, as a normal vector should be normalized anyway, and we want as many points as possible on the sphere around (0,0,0) with a radius of 1, and we don't care about precision around the origin. Even if we have large textures such as 4k by 4k (or the maximum allowed by D3D11, 16k by 16k) we only need as many grid-points on one axis, as there are pixels on one axis. An unsigned normalized 14 bit integer would be ideal, but because it is both unsupported and impractical, we will stick to an unsigned normalized 16 bit integer. The same type should take care of the normal vector coordinates, and might even be a bit overkill.
struct VertexData { float[3] position; //3x32-bits uint16_t[2] texCoord; //2x16bits uint16_t[3] normals; //3x16bits } //Total of 22 bytes Seems like a good start, and we might even be able to take it further, but before we pursue that path, here is my first question: can the GPU even work with the data in this format, or is all I have accomplished minimizing CPU-side RAM usage? Does the GPU have to convert the texture coordinates back to a floating-point model when I hand them over to the sampler in my pixel shader? I have looked up the data types for HLSL and I am not sure I even comprehend how to declare the vertex input type in HLSL. Would the following work?
struct VertexInputType { float3 pos; //this one is obvious unorm half2 tex; //half corresponds to a 16-bit float, so I assume this is wrong, but this the only 16-bit type I found on the linked MSDN site snorm half3 normal; //same as above } I assume this is possible somehow, as I have found input element formats such as: DXGI_FORMAT_R16G16B16A16_SNORM and DXGI_FORMAT_R16G16B16A16_UNORM (also available with a different number of components, as well as different component lengths). I might have to avoid 3-component vectors because there is no 3-component 16-bit input element format, but that is the least of my worries. The next question would be: what happens with my normals if I try to do lighting calculations with them in such a normalized-fixed-point format? Is there no issue as long as I take care not to mix floating- and fixed-point data? Or would that work as well? In general this gives rise to the question: how does the GPU handle fixed-point arithmetic? Is it the same as integer-arithmetic, and/or is it faster/slower than floating-point arithmetic?
Assuming that we still have a valid and useful VertexData format, how far could I take this while remaining on the sensible side of what could be called optimization? Theoretically I could use the an input element format such as DXGI_FORMAT_R10G10B10A2_UNORM to pack my normal coordinates into a 10-bit fixed-point format, and my verticies (in object space) might even be representable in a 16-bit unsigned normalized fixed-point format. That way I could end up with something like the following struct:
struct VertexData { uint16_t[3] pos; //3x16bits uint16_t[2] texCoord; //2x16bits uint32_t packedNormals; //10+10+10+2bits } //Total of 14 bytes Could I use a vertex structure like this without too much performance-loss on the GPU-side? If the GPU has to execute some sort of unpacking algorithm in the background I might as well let it be. In the end I have a functioning deferred renderer, but I would like to reduce the memory footprint of the huge amount of vertecies involved in rendering my landscape.
TLDR: I have a lot of vertices that I need to render and I want to reduce the RAM-usage without introducing crazy compression/decompression algorithms to the CPU or GPU. I am hoping to find a solution by involving fixed-point data-types, but I am not exactly sure how how that would work.
• By cozzie
Hi all,
I was wondering it it matters in which order you draw 2D and 3D items, looking at the BeginDraw/EndDraw calls on a D2D rendertarget.
The order in which you do the actual draw calls is clear, 3D first then 2D, means the 2D (DrawText in this case) is in front of the 3D scene.
The question is mainly about when to call the BeginDraw and EndDraw.
Note that I'm drawing D2D stuff through a DXGI surface linked to the 3D RT.
Option 1:
A - Begin frame, clear D3D RT
B - Draw 3D
C - BeginDraw D2D RT
D - Draw 2D
E - EndDraw D2D RT
F - Present
Option 2:
A - Begin frame, clear D3D RT + BeginDraw D2D RT
B - Draw 3D
C - Draw 2D
D - EndDraw D2D RT
E- Present
Would there be a difference (performance/issue?) in using option 2? (versus 1)
Any input is appreciated.

• Do you know any papers that cover custom data structures like lists or binary trees implemented in hlsl without CUDA that work perfectly fine no matter how many threads try to use them at any given time?
• By cozzie
Hi all,
Last week I noticed that when I run my test application(s) in Renderdoc, it crashes when it enable my code that uses D2D/DirectWrite. In Visual Studio no issues occur (debug or release), but when I run the same executable in Renderdoc, it crashes somehow (assert of D2D rendertarget or without any information). Before I spend hours on debugging/ figuring it out, does someone have experience with this symptom and/or know if Renderdoc has known issues with D2D? (if so, that would be bad news for debugging my application in the future );
I can also post some more information on what happens, code and which code commented out, eliminates the problems (when running in RenderDoc).
Any input is appreciated.

• Hi Guys,
I understand how to create input layouts etc... But I am wondering is it at all possible to derive an input layout from a shader and create the input layout directly from this? (Rather than manually specifying the input layout format?)