imfx

imfx is a lightweight shader-driven animated texture framework designed as an addon for Dear ImGui. It allows you to feed pixel shaders from strings, files, or raw byte blobs into a global context, modulate parameters in real-time, and bake them into standard textures (ImTextureID) for immediate rendering within your ImGui UI layouts.

Note: This is just a fun little side project I put together with the help of Claude Sonnet 4.6. I'm mainly just throwing it up here to share with the community, so feel free to play around with it!

Co-authored by Averta047 and Claude Sonnet 4.6

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Features

• Works with any renderer — The core layout and effect settings do not care what graphics API you use, making it completely backend-independent
• Easy shader loading — Load shader code from raw strings, files on disk, or pre-compiled binary blobs (CSO)
• Matches ImGui style — Context creation, frame update, and shutdown follow the exact same pattern as standard ImGui modules
• Built-in default effect — Ships with a cloudy fluid smoke shader ready to use out of the box
• BackBuffer input — Pass any texture (a live captured frame, another effect's output, a scene render target) directly into your shader via BackBufferSrv
• MSAA — Render targets are created with the best MSAA level supported by the device
• DirectX 11 backend included — Fully working DX11 backend wrapper with DXGI desktop capture helper

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Known Limitations

• Shaders depend on the renderer language — The shader code you pass must match the graphics API in use, controlled by the ImFXShaderLang enum. Switching backends means updating your shader source
• Only DirectX 11 / HLSL supported for now — Other backends and shader languages are future work

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Showcase

demo1.mp4

demo2.mp4

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Project Structure

imfx/
├── imfx.h                          # Core context, effect struct, public API
├── imfx.cpp                        # Context and effect management
├── imfx_impl_dx11.h                # DX11 backend header
├── imfx_impl_dx11.cpp              # DX11 backend implementation
├── imfx_capture_dxgi.h             # DXGI desktop capture helper header
├── imfx_capture_dxgi.cpp           # DXGI desktop capture helper implementation
└── samples/
    ├── shader_backbuffer/          # GPU-generated texture fed into a distortion shader
    │   ├── main.cpp
    │   └── impl/
    │       ├── includes.h
    │       └── shader.h
    └── dxgi_backbuffer/            # Live desktop capture fed into a depth reconstruction shader
        ├── main.cxx
        └── impl/
            ├── includes.h
            └── shader.h

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Usage

1 — Initialization

// Create the ImFX context (call before any effect creation)
ImFX::CreateContext();

// Initialize the DX11 backend
ImFX_ImplDX11_InitInfo info;
info.Device              = pDevice;
info.DeviceContext       = pDeviceContext;
info.CreateDefaultEffect = true;                    // Creates Effects[0], the built-in fluid smoke
info.DefaultEffectSize   = ImVec2(1280.0f, 720.0f);
ImFX_ImplDX11_Init(&info);

// Tweak default effect params
if (info.CreateDefaultEffect)
{
    ImFXEffect* def = ImFX::GetContext()->DefaultEffect;
    def->Speed   = 0.6f;
    def->Scale   = 2.5f;
    def->Density = 0.1f;
    def->ColorA  = ImVec4(0.0f,  0.0f,  0.0f,  0.0f);
    def->ColorB  = ImVec4(0.30f, 0.30f, 0.30f, 0.5f);
}

// Register a custom effect from a shader string
ImFXEffect* voronoi = ImFX::CreateEffectFromString(
    g_VoronoiShader, ImFXShaderLang_HLSL, ImVec2(800.0f, 600.0f));

voronoi->Speed   = 1.2f;
voronoi->Scale   = 3.5f;
voronoi->Density = 0.3f;
voronoi->ColorA  = ImVec4(0.02f, 0.02f, 0.08f, 1.0f);
voronoi->ColorB  = ImVec4(0.20f, 0.60f, 0.90f, 1.0f);

You can also load from a file or a pre-compiled CSO blob:

ImFXEffect* fromFile  = ImFX::CreateEffectFromFile("shaders/noise.hlsl", ImFXShaderLang_HLSL, size);
ImFXEffect* fromBytes = ImFX::CreateEffectFromBytes(csoData, csoSize, ImFXShaderLang_CSO, size);

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2 — Frame Update

// ImFX must update before ImGui's frame starts
ImFX_ImplDX11_NewFrame();
ImFX_ImplDX11_UpdateEffects(ImFX::GetContext());

// Then the standard ImGui frame
ImGui_ImplDX11_NewFrame();
ImGui_ImplWin32_NewFrame();
ImGui::NewFrame();

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3 — Rendering

// Default built-in effect
ImFXEffect* def = ImFX::GetContext()->DefaultEffect;
ImGui::Image(def->GetTexture(), def->Size);

// Any custom effect by index
ImFXEffect* voronoi = ImFX::GetContext()->Effects[1];
ImGui::Image(voronoi->GetTexture(), voronoi->Size);

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4 — Cleanup

// ImFX shutdown before standard ImGui shutdown
ImFX_ImplDX11_Shutdown();
ImFX::DestroyContext();

// Standard ImGui cleanup
ImGui_ImplDX11_Shutdown();
ImGui_ImplWin32_Shutdown();
ImGui::DestroyContext();

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BackBuffer Input

Every ImFXEffect has a BackBufferSrv field. Assign any ID3D11ShaderResourceView* to it before UpdateEffects and the backend binds it to t0 / s0 inside your pixel shader for that frame. The pointer is consumed and cleared to nullptr after the draw, so you must re-assign every frame you want it bound.

// Assign before UpdateEffects - consumed and cleared after the draw
myEffect->BackBufferSrv = (void*)pSomeSrv;

ImFX_ImplDX11_NewFrame();
ImFX_ImplDX11_UpdateEffects(ImFX::GetContext());

Inside your HLSL, declare the input at t0 / s0:

Texture2D    BackBuffer  : register(t0);
SamplerState BackSampler : register(s0);

float4 main(PS_IN i) : SV_TARGET
{
    float4 scene = BackBuffer.Sample(BackSampler, i.uv);
    // distort, tint, blur, composite...
    return scene;
}

You can confirm it was bound by checking the backend flag:

bool bound = (myEffect->_BackendFlags & ImFXEffectBackendFlags_BackBufferBound) != 0;

Two patterns are shown in the samples:

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Pattern A — Shader as BackBuffer (samples/shader_backbuffer)

Chain two effects together. The first effect renders a procedural pattern (the built-in fluid smoke); its output SRV is fed into a second effect that distorts it with a sine-wave warp.

Effects[0]  fluid smoke  ──► GetTexture()
                                  │
                          BackBufferSrv (assigned before UpdateEffects)
                                  │
                                  ▼
Effects[1]  sine distort  ──► GetTexture()  ──►  ImGui::Image()

Because UpdateEffects processes effects in array order, Effects[0] always renders before Effects[1] in the same call, so assigning Effects[0]->GetTexture() before the call gives Effects[1] the current frame's output with no lag.

// Before UpdateEffects each frame:
distort->BackBufferSrv = (void*)fluid->GetTexture();

ImFX_ImplDX11_NewFrame();
ImFX_ImplDX11_UpdateEffects(ImFX::GetContext());

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Pattern B — DXGI Desktop Capture as BackBuffer (samples/dxgi_backbuffer)

Use ImFXCapture_DXGI to grab the live desktop frame and feed it into a shader effect. This uses IDXGIOutputDuplication, the same API used by screen recorders and overlays — the desktop frame arrives as a GPU texture with no CPU round-trip.

Desktop (DWM compositor output)
         │
  IDXGIOutputDuplication::AcquireNextFrame()
         │
  CopyResource() ──► staging texture (BIND_SHADER_RESOURCE)
         │
  BackBufferSrv
         │
         ▼
ImFX effect  ──►  GetTexture()  ──►  ImGui::Image()
         │
  ReleaseFrame()   ← must call AFTER UpdateEffects

ImFXCapture_DXGI capture;
capture.Init(pDevice, pCtx, 0 /*primary monitor*/);

// Each frame, before UpdateEffects:
ID3D11ShaderResourceView* srv = capture.AcquireFrame();
if (srv)
    myEffect->BackBufferSrv = (void*)srv;

ImFX_ImplDX11_NewFrame();
ImFX_ImplDX11_UpdateEffects(ImFX::GetContext());

capture.ReleaseFrame(); // always call, even if AcquireFrame returned nullptr

ImFXCapture_DXGI handles resolution changes (DXGI_ERROR_ACCESS_LOST) automatically if you check IsReady() after AcquireFrame and call Shutdown() / Init() again when it returns false.

Note: DXGI Output Duplication requires Windows 8+ and a hardware DX11 device. It will fail on Remote Desktop sessions — check Init()'s return value and surface LastError() if it does.

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cbuffer Layout

All effects share the same constant buffer layout. Your pixel shader must declare it exactly as shown:

cbuffer ImFXParamCB : register(b0)
{
    float2 Resolution;  // render target size in pixels
    float  Time;        // accumulated time in seconds
    float  Speed;       // effect->Speed
    float  Scale;       // effect->Scale
    float  Density;     // effect->Density
    float2 _Pad;
    float4 ColorA;      // effect->ColorA
    float4 ColorB;      // effect->ColorB
};

BackBuffer / BackSampler at t0 / s0 are optional — only declare them if you assign BackBufferSrv.

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Future Ideas

• Texture inputs — Pass custom textures directly as named shader parameters
• Extra custom parameters — Expand the cbuffer so effects can receive arbitrary user data
• OpenGL / Vulkan backends — GLSL support when a new backend is added

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License

This is free and unencumbered code released into the public domain. Do whatever you want with it.