# DX11 Best practice for presenting enumerated display modes?

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We're currently working on the video settings UI for our project, and we've run into a bit of a presentation issue regarding the enumerated display modes. In our past DX9 projects, we presented a list of modes to the user in the following format:

<width> x <height>, (<refresh rate> Hz[, Widescreen])

However the issue in DX11 is that multiple display modes can be enumerated that have different refresh rate numerators and denominators, yet result in the same integral value when divided, regardless of rounding (i.e. 59940 / 1000 and 59950 / 1000). Plus, multiple display modes can have identical widths, heights, and refresh rate ratios, yet have different scaling values (unspecified, centered, stretched).

My question is, what's the best practice for building a list of unique resolutions for presenting to the user? We'd like to keep it simple so that the user is only making a choice based on width, height, and integral refresh rate (numerator / denominator), however if multiple display modes have the same values, which one takes precedence? Why would I choose 59940 over 59950?

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The easiest way is to choose which display modes you are interested in as game designer, check if they are available on client side, and display those which are correct. I dont think you need to display all.

Cheers.

Edited by wormpattern

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The easiest way is to choose which display modes you are interested in as game designer, check if they are available on client side, and display those which are correct. I dont think you need to display all.

Cheers.

Even so, let's say I want to include 1920x1080 in the list. When I enumerate the display modes, I get five different modes with that resolution. One is 50Hz, and four are 60Hz (either 59940 / 1000 or 59950 / 1000). At the latter ratio, there is one mode for each of three scaling types (unspecified, centered, and stretched). Out of the four 60Hz modes, which one do I choose? Even if we ignore the scaling type, there's still two 60Hz modes, and when we create the swap chain we have to choose one set of ratios... I'm just not 100% clear on the implications of choosing one ratio over another.

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• By cozzie
Hi all,
It's been a while since I've been working on my HLSL shaders, and found out I'm not 100% sure if I'm applying gamma correctness correctly. So here's what I do:
- create backbuffer in this format: DXGI_FORMAT_R8G8B8A8_UNORM_SRGB
- source textures (DDS) are always in SRGB format
- this way the textures should be gamma correct, because DX11 helps me out here
Now my question is about material and light colors. I'm not sure if I need to convert those to linear space. The colors are handpicked on screen, so I guess gamma correct. Below are 2 screenshots, the darker is including converting those colors (return float4(linearColor.rgb * linearColor.rgb, linearColor.a);), in the lighter shot I didn't do this conversion.
These are the properties of the brick material and the light source (there are no other lightsources in the scene, also no global ambient):
Material:
CR_VECTOR4(0.51f, 0.26f, 0.22f, 1.0f), // ambient CR_VECTOR4(0.51f, 0.26f, 0.22f, 1.0f), // diffuse RGB + alpha CR_VECTOR4(0.51f, 0.26f, 0.22f, 4.0f)); // specular RGB + power Directional light:
mDirLights[0].Ambient = CR_VECTOR4(0.1f, 0.1f, 0.1f, 1.0f); mDirLights[0].Diffuse = CR_VECTOR4(0.75f, 0.75f, 0.75f, 1.0f); mDirLights[0].Specular = CR_VECTOR4(1.0f, 1.0f, 1.0f, 16.0f); mDirLights[0].Direction = CR_VECTOR3(0.0f, 1.0f, 0.0f);
So in short, should I or should I not do this conversion in the lighting calculation in the shader? (and/or what else are you seeing :))
Note that I don't do anything with the texture color, after it's fetched in the shader (no conversions), which I believe is correct.

• 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.