graphics-api-hooking（graphics API hooking 文档）

Graphics API Hooking & Rendering

Overview

This skill covers graphics API resources from the awesome-game-security collection, including DirectX, OpenGL, and Vulkan hooking techniques, overlay rendering, and graphics debugging.

README Coverage

• DirectX > Guide
• DirectX > Hook
• DirectX > Tools
• DirectX > Emulation
• DirectX > Compatibility
• DirectX > Overlay
• OpenGL > Guide
• OpenGL > Source
• OpenGL > Hook
• Vulkan > Guide
• Vulkan > API
• Vulkan > Hook
• Cheat > Overlay
• Cheat > Render/Draw
• Cheat > Anti Screenshot
• Anti Cheat > Screenshot
• Anti Cheat > Detection:Overlay

DirectX

DirectX 9

// Key functions to hook
IDirect3DDevice9::EndScene
IDirect3DDevice9::Reset
IDirect3DDevice9::Present

DirectX 11

// Key functions to hook
IDXGISwapChain::Present
ID3D11DeviceContext::DrawIndexed
ID3D11DeviceContext::Draw

DirectX 12

// Key functions to hook
IDXGISwapChain::Present
ID3D12CommandQueue::ExecuteCommandLists

VTable Hooking

// DX11 Example
typedef HRESULT(__stdcall* Present)(IDXGISwapChain*, UINT, UINT);
Present oPresent;

HRESULT __stdcall hkPresent(IDXGISwapChain* swapChain, UINT syncInterval, UINT flags) {
    // Render overlay here
    return oPresent(swapChain, syncInterval, flags);
}

// Hook via vtable
void* swapChainVtable = *(void**)swapChain;
oPresent = (Present)swapChainVtable[8];  // Present is index 8

OpenGL

Key Functions

wglSwapBuffers
glDrawElements
glDrawArrays
glBegin/glEnd (legacy)

Hook Example

typedef BOOL(WINAPI* wglSwapBuffers_t)(HDC);
wglSwapBuffers_t owglSwapBuffers;

BOOL WINAPI hkwglSwapBuffers(HDC hdc) {
    // Render overlay
    return owglSwapBuffers(hdc);
}

Vulkan

Key Functions

vkQueuePresentKHR
vkCreateSwapchainKHR
vkCmdDraw
vkCmdDrawIndexed

Instance/Device Layers

• Use validation layers for debugging
• Custom layers for interception
• Layer manifest configuration

Universal Hook Libraries

Kiero

• Cross-API hook library
• Supports DX9/10/11/12, OpenGL, Vulkan
• Automatic method detection

Universal ImGui Hook

• Pre-built ImGui integration
• Multiple API support
• Easy deployment

ImGui Integration

Setup (DX11)

// In Present hook
ImGui_ImplDX11_Init(device, context);
ImGui_ImplWin32_Init(hwnd);

// Render
ImGui_ImplDX11_NewFrame();
ImGui_ImplWin32_NewFrame();
ImGui::NewFrame();

// Your rendering code
ImGui::Begin("Overlay");
// ...
ImGui::End();

ImGui::Render();
ImGui_ImplDX11_RenderDrawData(ImGui::GetDrawData());

Window Procedure Hook

// Required for ImGui input
LRESULT CALLBACK WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam) {
    if (ImGui_ImplWin32_WndProcHandler(hWnd, msg, wParam, lParam))
        return true;
    return CallWindowProc(oWndProc, hWnd, msg, wParam, lParam);
}

Overlay Techniques

External Overlay

1. Create transparent window
2. Set WS_EX_LAYERED | WS_EX_TRANSPARENT
3. Use SetLayeredWindowAttributes
4. Render with GDI+/D2D
5. Position over game window

DWM Overlay

- Hook Desktop Window Manager
- Render in DWM composition
- Higher privilege requirements
- Better anti-detection

Steam Overlay Hijack

- Hook Steam's overlay functions
- Use existing overlay infrastructure
- Requires Steam running

NVIDIA Overlay Hijack

- Hook GeForce Experience overlay
- Native-looking overlay
- May require specific drivers

Shader Manipulation

Wallhack Implementation

// Disable depth testing
OMSetDepthStencilState(depthDisabledState, 0);

// Or in pixel shader
float4 PSMain(VS_OUTPUT input) : SV_Target {
    // Always pass depth test
    return float4(1, 0, 0, 0.5);  // Red transparent
}

Chams (Character Highlighting)

// Replace model shader
float4 PSChams(VS_OUTPUT input) : SV_Target {
    if (isEnemy) {
        return float4(1, 0, 0, 1);  // Red
    }
    return float4(0, 1, 0, 1);      // Green
}

Rendering Concepts

World-to-Screen

D3DXVECTOR3 WorldToScreen(D3DXVECTOR3 pos, D3DXMATRIX viewProjection) {
    D3DXVECTOR4 clipCoords;
    D3DXVec3Transform(&clipCoords, &pos, &viewProjection);

    if (clipCoords.w < 0.1f) return invalid;

    D3DXVECTOR3 NDC;
    NDC.x = clipCoords.x / clipCoords.w;
    NDC.y = clipCoords.y / clipCoords.w;

    D3DXVECTOR3 screen;
    screen.x = (viewport.Width / 2) * (NDC.x + 1);
    screen.y = (viewport.Height / 2) * (1 - NDC.y);

    return screen;
}

View Matrix Extraction

- From device constants
- Pattern scanning
- Engine-specific locations
- Reverse engineered addresses

Debugging Tools

PIX for Windows

• Frame capture and analysis
• GPU profiling
• Shader debugging

RenderDoc

• Open-source frame debugger
• Multi-API support
• Resource inspection

NVIDIA Nsight

• Performance analysis
• Shader debugging
• Frame profiling

Anti-Screenshot Techniques

How Anti-Cheat Captures Screenshots

- BitBlt from game window DC: captures visible content including overlays
- DXGI Desktop Duplication API: captures composited desktop output
- IDXGISwapChain::Present interception: grab backbuffer before present
- PrintWindow: capture specific window contents
- DirectX/Vulkan frame readback: copy render target to CPU-readable buffer
- Scheduled captures: random intervals to catch intermittent overlays

Overlay Evasion Against Screenshot

- Disable overlay rendering during screenshot frame:
  - Detect screenshot by hooking BitBlt/PrintWindow in AC module
  - Suppress ImGui rendering for captured frame
- DWM composition tricks:
  - Render to a separate window that DWM excludes from capture
  - Use WDA_EXCLUDEFROMCAPTURE (SetWindowDisplayAffinity) on overlay window
- Hardware overlay planes:
  - Use IDXGIOutput::FindClosestMatchingMode + hardware overlay
  - Content on hardware overlay plane may not appear in software capture
- External rendering:
  - Render on secondary display or capture card output
  - OBS virtual camera trick: render to virtual camera feed

Cheat-Side Anti-Screenshot (README > Anti Screenshot)

- Projects that detect and evade AC screenshot capture
- Techniques: hook Present to suppress overlay on screenshot frames
- DWM-based overlays that survive PrintWindow but not BitBlt
- Kernel-level: suppress screenshot by blocking DC access

Anti-Detection Considerations

Present Hook Detection

- VTable integrity checks
- Code section verification
- Call stack analysis

Evasion Techniques

- Trampoline hooks
- Hardware breakpoints
- Timing obfuscation

Performance Optimization

Best Practices

1. Minimize state changes
2. Batch draw calls
3. Use instancing
4. Cache resources
5. Profile regularly

Common Issues

- Flickering: Double buffer sync
- Artifacts: Clear state properly
- Performance: Reduce overdraw

Resource Organization

The README contains:

• DirectX 9/11/12 hook implementations
• OpenGL hook libraries
• Vulkan interception tools
• ImGui integration examples
• Overlay frameworks
• Shader modification tools

Data Source

Important: This skill provides conceptual guidance and overview information. For detailed information use the following sources:

1. Project Overview & Resource Index

Fetch the main README for the full curated list of repositories, tools, and descriptions:

https://raw.githubusercontent.com/gmh5225/awesome-game-security/refs/heads/main/README.md

The main README contains thousands of curated links organized by category. When users ask for specific tools, projects, or implementations, retrieve and reference the appropriate sections from this source.

2. Repository Code Details (Archive)

For detailed repository information (file structure, source code, implementation details), the project maintains a local archive. If a repository has been archived, always prefer fetching from the archive over cloning or browsing GitHub directly.

Archive URL format:

https://raw.githubusercontent.com/gmh5225/awesome-game-security/refs/heads/main/archive/{owner}/{repo}.txt

Examples:

https://raw.githubusercontent.com/gmh5225/awesome-game-security/refs/heads/main/archive/ufrisk/pcileech.txt
https://raw.githubusercontent.com/gmh5225/awesome-game-security/refs/heads/main/archive/000-aki-000/GameDebugMenu.txt

How to use:

1. Identify the GitHub repository the user is asking about (owner and repo name from the URL).
2. Construct the archive URL: replace {owner} with the GitHub username/org and {repo} with the repository name (no .git suffix).
3. Fetch the archive file — it contains a full code snapshot with file trees and source code generated by code2prompt.
4. If the fetch returns a 404, the repository has not been archived yet; fall back to the README or direct GitHub browsing.

3. Repository Descriptions

For a concise English summary of what a repository does, the project maintains auto-generated description files.

Description URL format:

https://raw.githubusercontent.com/gmh5225/awesome-game-security/refs/heads/main/description/{owner}/{repo}/description_en.txt

Examples:

https://raw.githubusercontent.com/gmh5225/awesome-game-security/refs/heads/main/description/00christian00/UnityDecompiled/description_en.txt
https://raw.githubusercontent.com/gmh5225/awesome-game-security/refs/heads/main/description/ufrisk/pcileech/description_en.txt

How to use:

1. Identify the GitHub repository the user is asking about (owner and repo name from the URL).
2. Construct the description URL: replace {owner} with the GitHub username/org and {repo} with the repository name.
3. Fetch the description file — it contains a short, human-readable summary of the repository's purpose and contents.
4. If the fetch returns a 404, the description has not been generated yet; fall back to the README entry or the archive.

Priority order when answering questions about a specific repository:

1. Description (quick summary) — fetch first for concise context
2. Archive (full code snapshot) — fetch when deeper implementation details are needed
3. README entry — fallback when neither description nor archive is available