Evolve Shader

中文说明 / Chinese README

Evolve Shader is a minimal multi-pass shader viewer inspired by Shadertoy. It loads fragment shaders from frag/, lets you wire iChannel0-iChannel3 interactively, renders every pass into ping-pong framebuffers, and presents the last pass to the window.

Screenshots

What This Repository Actually Contains

Evolve-Shader/
├─ main.cpp
├─ include/
│  ├─ ChannelConfig.h
│  ├─ GLTypes.h
│  ├─ Resources.h
│  ├─ ShaderIO.h
│  └─ ShaderProgram.h
├─ frag/
│  ├─ 1.frag
│  └─ 2.frag
├─ iChannel/
│  ├─ bw_noise.png
│  ├─ color_noise.png
│  ├─ london.png
│  └─ rock.png
├─ CMakeLists.txt
├─ LICENSE
└─ readme.md

Features

• Shadertoy-style shader entry via mainImage(out vec4 fragColor, in vec2 fragCoord).
• Multi-pass rendering driven by the numeric order of .frag files in frag/.
• Interactive iChannel routing for none, self, other buffers, or images from iChannel/.
• Ping-pong framebuffer feedback for recursive / temporal effects.
• Common Shadertoy uniforms such as iResolution, iTime, iMouse, iDate, and iChannelResolution.
• Lazy global texture cache for images discovered under iChannel/.
• Preset System: Save your configuration (channels + shader files + images) to a folder and reload it later.
• FPS shown in the window title.

Runtime Behavior

At startup the app does the following:

1. Checks for presets in presets/.
2. If presets exist, asks to load one or start new.
3. If new configuration selected: a. Scans iChannel/ recursively for .png, .jpg, and .jpeg images. b. Scans frag/ non-recursively for .frag files. c. Sorts shader passes by the first number found in each filename. d. Prompts you to configure iChannel0-iChannel3 for each pass. e. Asks if you want to save the configuration as a new preset.
4. Renders all passes off-screen, then displays the last pass on screen.

Important behavior details:

• Files in frag/ without a number in the filename are ignored.
• frag/ is not scanned recursively.
• iChannel/ is scanned recursively.
• On the very first frame, buffer inputs fall back to an empty texture.
• Configured global images are preloaded before the render loop starts.
• VSync is disabled by default. Use the startup Settings menu to toggle VSync on/off.

Shader Pass Ordering

The renderer uses the first numeric token in the filename to determine pass order.

Recommended naming:

0_main.frag
1_blur.frag
2_feedback.frag
3_present.frag

Current repository examples use:

frag/1.frag
frag/2.frag

Supported Uniforms

The wrapper injected by include/ShaderIO.h exposes these uniforms:

Uniform	Type	Notes
iResolution	vec3	Framebuffer size in pixels; current code sets z = 1.0.
iTime	float	Seconds since startup.
iTimeDelta	float	Time between frames.
iFrame	int	Frame counter.
iFrameRate	float	Computed from iTimeDelta.
iDate	vec4	Year, month, day, seconds since midnight.
iMouse	vec4	Shadertoy-like mouse state.
iChannel0-iChannel3	sampler2D	Texture or buffer inputs.
iChannelTime[4]	float[4]	Currently all set to iTime.
iChannelResolution[4]	vec3[4]	Bound texture resolution for each channel.
iSampleRate	float	Currently fixed to 44100.0.

iMouse follows Shadertoy-style semantics:

• xy: current mouse position in pixels, origin at bottom-left.
• zw: current press position while the button is down; negative last click position after release.

Dependencies

The CMake build fetches third-party source trees into 3rd/ automatically:

• OpenGL 3.3 compatible GPU / driver
• glfw3
• glew
• stb_image.h

You only need CMake, a C++17 compiler, Git, and platform OpenGL development support.

Cross-Platform CMake Build

Windows

Install Visual Studio 2022 with the C++ workload, CMake, and Git. Then run:

cmake -S . -B build
cmake --build build --config Release

macOS

Install Xcode Command Line Tools, CMake, and Git. Then run:

cmake -S . -B build
cmake --build build --config Release

Linux

Install CMake, Git, a C++17 compiler, and OpenGL/X11 development packages. For example, on Ubuntu/Debian:

sudo apt install build-essential cmake git libgl1-mesa-dev xorg-dev

Then run:

cmake -S . -B build
cmake --build build --config Release

Run

CMake copies frag/, iChannel/, and presets/ next to the executable after each build, so you can run from the build output directory:

./build/EvolveShader

For multi-config generators such as Visual Studio, run the executable under the configuration folder, for example build/Release/EvolveShader.exe.

Usage

Quick start

1. Put one or more .frag files in frag/.
2. Optionally put images in iChannel/.
3. Launch the app.
4. Press Enter to use the automatic pass chain, or type a pass index to configure channels manually.

Automatic chain mode

If you press Enter at the first prompt, the renderer creates a simple chain:

• pass 2 reads pass 1 in iChannel0
• pass 3 reads pass 2 in iChannel0
• and so on

Manual mode

For a selected pass, each channel can be assigned to:

• none
• self for feedback
• another previously or later defined buffer
• a global image from iChannel/

Example Shader

void mainImage(out vec4 fragColor, in vec2 fragCoord)
{
    vec2 uv = fragCoord / iResolution.xy;
    fragColor = vec4(uv, 0.5 + 0.5 * sin(iTime), 1.0);
}

You do not need to provide main() yourself. The runtime wraps your shader automatically.

Notes and Limitations

• Third-party sources are fetched into 3rd/ during CMake configure.
• Channel configuration can be saved as a preset when prompted at startup.
• On Windows, macOS, and Linux, saved changes under the active frag/ directory trigger an immediate shader reload. A failed compile keeps the last working shader on screen.
• For live editing from Visual Studio, the debugger runs from the repository root automatically. From a terminal, run build/Release/EvolveShader.exe while your current directory is the repository root so edits to frag/ are watched directly.
• The last pass is always the one presented to the screen.
• Image bindings are preloaded after configuration.
• The sample shaders in frag/ include their own upstream attribution comments.

License

The project is distributed under the Apache License 2.0. See LICENSE.

Third-party shader or image assets may have their own licenses or attribution requirements.