README.md

Shader Presets

A package that implements some ready-to-use shaders, like transitions from gl-transitions and effects from ShaderToy.

It uses the shader_buffers package which simplifies the use of shaders.

There are few presets and more can be added quite easily.

Seems that impeller engine is not yet ready, on iOS it should work with impeller disabled.

Getting Started

Simply as:

final presetController = ShaderPresetController();
ShaderPresetCube(
    child1: child1, // children can be either the path to the asset image or a widget
    child2: child2,
    presetController: presetController,
    progress: 0, // This is common to all gl-transitions
    reflection: 1, // This is one parameter of this Cube shader
)

presetController lets you get/set uniforms and get the shader controller. The Shader controller lets you play/pause/rewind, add conditionals operation to check pointer position, get its state, swap texture channels, and animate custom uniform values.

animate a custom uniform:

presetController.getShaderController()!.animateUniform(
    uniformName: 'progress',
    begin: 0,
    end: 1,
    duration: const Duration(milliseconds: 600),
    curve: Curves.decelerate,
    onAnimationEnded: (ctrl, uniformValue) {
        ...
    },
);

Here all the current presets available with their uniform parameters, many others can be easily added:

from ShaderToy
ShaderPresetBarrel distortion
ShaderPresetWater speed, frequency, amplitude
ShaderPresetPageCurl radius

from gl-transitions
ShaderPresetCube progress, persp, unzoom, reflection, floating
ShaderPresetPolkaDotsCurtain progress, dots, centerX, centerY
ShaderPresetRadial progress, smoothness
ShaderPresetFlyeye progress, size, zoom, colorSeparation

Contributing

Adding a preset

In shader_presets.dart

• add a [ShaderPresetsEnum] enum value
• add that enum in [ShaderPresetController.getUniforms()] method. If the new shader doesn't have additional float uniforms, then return an empty list
• write the [StatelessWidget] class (see src/gl_transitions/ or src/shadertoy folder for reference)
• add a shader reference in shaders section of pubspec.yaml to your fragment source

The dynamic child represents the texture (the uniform sampler2D in the shader source) the shader uses. It must be the asset image path or a Widget. You can add as many children as you wish based on the fragment usage.

Add/Write the fragment shader

There are some common headers to put at the beginning or at the end of the fragment source:

common_header.frag this is common to all the sources. It defines the common uniforms the shader_buffers package uses and the uniforms it adds can be used when writing your own fragment and must be imported in the first line of the fragment source:

uniform vec2 iResolution; // The viewport resolution in pixels
uniform float iTime;      // The shader playback time (in seconds)
uniform float iFrame;     // The shader playback frame
uniform vec4 iMouse;      // Mouse pixel coords. xy: current (if MLB down), zw: click

out vec4 fragColor;       // The shader output

These uniforms are also useful when using a fragment from ShaderToy.

common_gl_transitions.frag this is the common header for gl_transitions sources and it adds:

uniform sampler2D iChannel0; // The 1st texture
uniform sampler2D iChannel1; // The 2nd texture

// a value that moves from 0.0 to 1.0 during the transition.
uniform float progress;
// the ratio of the viewport. It equals width / height.
float ratio;

It also adds getFromColor and getToColor functions commonly used in gl-transitions shaders.

There are also other two sources to import at the end of the source code: main_shadertoy.frag and main_gl_transitions.frag

gl-transition example

// mandatory include for all fragment sources
#include "../common/common_header.frag"
// mandatory include for gl-transitions sources
#include "../common/common_gl_transitions.frag"

//------------------ Here starts gl-transition source
...
//------------------ Here ends gl-transition source

// mandatory include for gl-transitions sources
#include "../common/main_gl_transitions.frag"

ShaderToy example

#include "../common/common_header.frag"

// Define here the iChannel[0-3] used in the source
uniform sampler2D iChannel0;

//------------------ Here starts ShaderToy source
...
//------------------ Here ends ShaderToy source


#include "../common/main_shadertoy.frag"