Sign in to follow this  

DX11 Instancing

Recommended Posts


I have been following [url=""]this tutorial[/url] , but while experimenting I reached a dead end. The addition I was trying to implement is a dynamic updating rotation per instance.

So first, i define

// TriangleTest.h
struct InstanceType
D3DXVECTOR3 position;
D3DXVECTOR3 rotation;
for my Instance buffer Type, which leads me to define

// vertexshader.vs
struct VertexInputType
float3 position : POSITION;
float4 color : COLOR;
float3 instancePosition : POSITION1;
float3 instanceRotation : POSITION2;
in my vertex Shader file. Note that I have changed the usage of semantic type TEXCOORD from the tutorial, as I feel more comfortable having positions use POSITION, as well as giving the position a [b]float3 type[/b].

I set up my InputElementDescription array like this

polygonLayout[0].SemanticName = "POSITION";
polygonLayout[0].SemanticIndex = 0;
polygonLayout[0].Format = DXGI_FORMAT_R32G32B32_FLOAT;
polygonLayout[0].InputSlot = 0;
polygonLayout[0].AlignedByteOffset = 0;
polygonLayout[0].InputSlotClass = D3D11_INPUT_PER_VERTEX_DATA;
polygonLayout[0].InstanceDataStepRate = 0;
polygonLayout[1].SemanticName = "COLOR";
polygonLayout[1].SemanticIndex = 0;
polygonLayout[1].Format = DXGI_FORMAT_R32G32B32A32_FLOAT;
polygonLayout[1].InputSlot = 0;
polygonLayout[1].AlignedByteOffset = D3D11_APPEND_ALIGNED_ELEMENT;
polygonLayout[1].InputSlotClass = D3D11_INPUT_PER_VERTEX_DATA;
polygonLayout[1].InstanceDataStepRate = 0;
polygonLayout[2].SemanticName = "POSITION";
polygonLayout[2].SemanticIndex = 1;
polygonLayout[2].Format = DXGI_FORMAT_R32G32B32_FLOAT;
polygonLayout[2].InputSlot = 1;
polygonLayout[2].AlignedByteOffset = 0;
polygonLayout[2].InputSlotClass = D3D11_INPUT_PER_INSTANCE_DATA;
polygonLayout[2].InstanceDataStepRate = 1;
polygonLayout[3].SemanticName = "POSITION";
polygonLayout[3].SemanticIndex = 2;
polygonLayout[3].Format = DXGI_FORMAT_R32G32B32_FLOAT;
polygonLayout[3].InputSlot = 1;
polygonLayout[3].AlignedByteOffset = D3D11_APPEND_ALIGNED_ELEMENT;
polygonLayout[3].InputSlotClass = D3D11_INPUT_PER_INSTANCE_DATA;
polygonLayout[3].InstanceDataStepRate = 1;

and create the input layouts.
In my model class (TriangeTest), i use this to update the dynamic instance buffer ( completely created as D3D11_USAGE_DYNAMIC, with D3D11_CP_ACCESS_WRITE)

void TriangleTest::Frame(ID3D11DeviceContext* deviceContext) {
for (int i = 0; i < this->i_instanceCount; i++) {
D3DXVec3Add(&(m_instanceList[i].rotation), &(m_instanceList[i].rotation), &D3DXVECTOR3(1,0,0.0f));
void TriangleTest::UpdateBuffers(ID3D11DeviceContext* deviceContext) {
HRESULT result;
D3D11_MAPPED_SUBRESOURCE mappedResource;
InstanceType* instancePtr;

result =deviceContext->Map(m_instanceBuffer, 0, D3D11_MAP_WRITE_DISCARD, 0, &mappedResource);
if(FAILED(result)) throw CException("Could not remap instance buffer");
instancePtr = (InstanceType*)mappedResource.pData;
memcpy(instancePtr, (void*)m_instanceList, (sizeof(InstanceType) * i_instanceCount));
deviceContext->Unmap(m_instanceBuffer, 0);
, where m_instanceList is an array of InstanceType holding all information on the position and rotation per triangle. Of course, theFrame(...) function gets called once per frame.

Then I use the shader as provided and replace instancePosition with [b]instanceRotation[/b],which should make my triangles slide out to the right.

PixelInputType TextureVertexShader(VertexInputType input)
PixelInputType output;

// Change the position vector to be 4 units for proper matrix calculations.
input.position.w = 1.0f;
Here is where we use the instanced position information to modify the position of each triangle we are drawing.
// Update the position of the vertices based on the data for this particular instance.
input.position.x += input.[b]instanceRotation[/b].x;
input.position.y += input.[b]instanceRotation[/b].y;
input.position.z += input.[b]instanceRotation[/b].z;
// Calculate the position of the vertex against the world, view, and projection matrices.
output.position = mul(input.position, worldMatrix);
output.position = mul(output.position, viewMatrix);
output.position = mul(output.position, projectionMatrix);

// Store the texture coordinates for the pixel shader.
output.tex = input.tex;

return output;

But when I run it (complete without errors), the triangles stay still on the screen. Even when using [b]instancePosition[/b] again. They move however, if I change the semantic type of inputPosition to TEXCOORD and update the position in the Frame procedure, but even then I get no motion from the instanceRotation.

Which leads me to think, that my InputElementLayoutDescription is wrong. But how? I have tried many a combination already, but don't understand.

Can anyone enlighten me with their ideas?

Share this post

Link to post
Share on other sites
That actually did the trick.
Thank you so very much, i thought I had tried this before, but my mind was so messed up with this, I screwed it completely and tested it with some update code disabled. I was already going to tell you how it doesn't work, but kept trying once more to consider your answer, and Voila.

It actually works.

Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

  • Announcements

  • Forum Statistics

    • Total Topics
    • Total Posts
  • Similar Content

    • By 51mon
      I want to change the sampling behaviour to SampleLevel(coord, ddx(coord.y).xx, ddy(coord.y).yy). I was just wondering if it's possible without explicit shader code, e.g. with some flags or so?
    • By GalacticCrew
      I want to improve the performance of my game (engine) and some of your helped me to make a GPU Profiler. After creating the GPU Profiler, I started to measure the time my GPU needs per frame. I refined my GPU time measurements to find my bottleneck.
      Searching the bottleneck
      Rendering a small scene in an Idle state takes around 15.38 ms per frame. 13.54 ms (88.04%) are spent while rendering the scene, 1.57 ms (10.22%) are spent during the SwapChain.Present call (no VSync!) and the rest is spent on other tasks like rendering the UI. I further investigated the scene rendering, since it takes über 88% of my GPU frame rendering time.
      When rendering my scene, most of the time (80.97%) is spent rendering my models. The rest is spent to render the background/skybox, updating animation data, updating pixel shader constant buffer, etc. It wasn't really suprising that most of the time is spent for my models, so I further refined my measurements to find the actual bottleneck.
      In my example scene, I have five animated NPCs. When rendering these NPCs, most actions are almost for free. Setting the proper shaders in the input layout (0.11%), updating vertex shader constant buffers (0.32%), setting textures (0.24%) and setting vertex and index buffers (0.28%). However, the rest of the GPU time (99.05% !!) is spent in two function calls: DrawIndexed and DrawIndexedInstance.
      I searched this forum and the web for other articles and threads about these functions, but I haven't found a lot of useful information. I use SharpDX and .NET Framework 4.5 to develop my game (engine). The developer of SharpDX said, that "The method DrawIndexed in SharpDX is a direct call to DirectX" (Source). DirectX 11 is widely used and SharpDX is "only" a wrapper for DirectX functions, I assume the problem is in my code.
      How I render my scene
      When rendering my scene, I render one model after another. Each model has one or more parts and one or more positions. For example, a human model has parts like head, hands, legs, torso, etc. and may be placed in different locations (on the couch, on a street, ...). For static elements like furniture, houses, etc. I use instancing, because the positions never change at run-time. Dynamic models like humans and monster don't use instancing, because positions change over time.
      When rendering a model, I use this work-flow:
      Set vertex and pixel shaders, if they need to be updated (e.g. PBR shaders, simple shader, depth info shaders, ...) Set animation data as constant buffer in the vertex shader, if the model is animated Set generic vertex shader constant buffer (world matrix, etc.) Render all parts of the model. For each part: Set diffuse, normal, specular and emissive texture shader views Set vertex buffer Set index buffer Call DrawIndexedInstanced for instanced models and DrawIndexed models What's the problem
      After my GPU profiling, I know that over 99% of the rendering time for a single model is spent in the DrawIndexedInstanced and DrawIndexed function calls. But why do they take so long? Do I have to try to optimize my vertex or pixel shaders? I do not use other types of shaders at the moment. "Le Comte du Merde-fou" suggested in this post to merge regions of vertices to larger vertex buffers to reduce the number of Draw calls. While this makes sense to me, it does not explain why rendering my five (!) animated models takes that much GPU time. To make sure I don't analyse something I wrong, I made sure to not use the D3D11_CREATE_DEVICE_DEBUG flag and to run as Release version in Visual Studio as suggested by Hodgman in this forum thread.
      My engine does its job. Multi-texturing, animation, soft shadowing, instancing, etc. are all implemented, but I need to reduce the GPU load for performance reasons. Each frame takes less than 3ms CPU time by the way. So the problem is on the GPU side, I believe.
    • By noodleBowl
      I was wondering if someone could explain this to me
      I'm working on using the windows WIC apis to load in textures for DirectX 11. I see that sometimes the WIC Pixel Formats do not directly match a DXGI Format that is used in DirectX. I see that in cases like this the original WIC Pixel Format is converted into a WIC Pixel Format that does directly match a DXGI Format. And doing this conversion is easy, but I do not understand the reason behind 2 of the WIC Pixel Formats that are converted based on Microsoft's guide
      I was wondering if someone could tell me why Microsoft's guide on this topic says that GUID_WICPixelFormat40bppCMYKAlpha should be converted into GUID_WICPixelFormat64bppRGBA and why GUID_WICPixelFormat80bppCMYKAlpha should be converted into GUID_WICPixelFormat64bppRGBA
      In one case I would think that: 
      GUID_WICPixelFormat40bppCMYKAlpha would convert to GUID_WICPixelFormat32bppRGBA and that GUID_WICPixelFormat80bppCMYKAlpha would convert to GUID_WICPixelFormat64bppRGBA, because the black channel (k) values would get readded / "swallowed" into into the CMY channels
      In the second case I would think that:
      GUID_WICPixelFormat40bppCMYKAlpha would convert to GUID_WICPixelFormat64bppRGBA and that GUID_WICPixelFormat80bppCMYKAlpha would convert to GUID_WICPixelFormat128bppRGBA, because the black channel (k) bits would get redistributed amongst the remaining 4 channels (CYMA) and those "new bits" added to those channels would fit in the GUID_WICPixelFormat64bppRGBA and GUID_WICPixelFormat128bppRGBA formats. But also seeing as there is no GUID_WICPixelFormat128bppRGBA format this case is kind of null and void
      I basically do not understand why Microsoft says GUID_WICPixelFormat40bppCMYKAlpha and GUID_WICPixelFormat80bppCMYKAlpha should convert to GUID_WICPixelFormat64bppRGBA in the end
    • By DejayHextrix
      Hi, New here. 
      I need some help. My fiance and I like to play this mobile game online that goes by real time. Her and I are always working but when we have free time we like to play this game. We don't always got time throughout the day to Queue Buildings, troops, Upgrades....etc.... 
      I was told to look into DLL Injection and OpenGL/DirectX Hooking. Is this true? Is this what I need to learn? 
      How do I read the Android files, or modify the files, or get the in-game tags/variables for the game I want? 
      Any assistance on this would be most appreciated. I been everywhere and seems no one knows or is to lazy to help me out. It would be nice to have assistance for once. I don't know what I need to learn. 
      So links of topics I need to learn within the comment section would be SOOOOO.....Helpful. Anything to just get me started. 
      Dejay Hextrix 
    • By GalacticCrew
      In some situations, my game starts to "lag" on older computers. I wanted to search for bottlenecks and optimize my game by searching for flaws in the shaders and in the layer between CPU and GPU. My first step was to measure the time my render function needs to solve its tasks. Every second I wrote the accumulated times of each task into my console window. Each second it takes around
      170ms to call render functions for all models (including settings shader resources, updating constant buffers, drawing all indexed and non-indexed vertices, etc.) 40ms to render the UI 790ms to call SwapChain.Present <1ms to do the rest (updating structures, etc.) In my Swap Chain description I set a frame rate of 60 Hz, if it's supported by the computer. It made sense for me that the Present function waits some time until it starts the next frame. However, I wanted to check, if this might be a problem for me. After a web search I found articles like this one, which states 
      My drivers are up-to-date so that's no issue. I installed Microsoft's PIX, but I was unable to use it. I could configure my game for x64, but PIX is not able to process DirectX 11.. After getting only error messages, I installed NVIDIA's NSight. After adjusting my game and installing all components, I couldn't get a proper result, because my game freezes after a few frames. I haven't figured out why. There is no exception or error message and other debug mechanisms like log messages and break points tell me the game freezes at the end of the render function after a few frames. So, I looked for another profiling tool and found Jeremy's GPUProfiler. However, the information returned by this tool is too basic to get an in-depth knowledge about my performance issues.
      Can anyone recommend a GPU Profiler or any other tool that might help me to find bottlenecks in my game and or that is able to indicate performance problems in my shaders? My custom graphics engine can handle subjects like multi-texturing, instancing, soft shadowing, animation, etc. However, I am pretty sure, there are things I can optimize!
      I am using SharpDX to develop a game (engine) based on DirectX 11 with .NET Framework 4.5. My graphics cards is from NVIDIA and my processor is made by Intel.
  • Popular Now