Custom Shaders

Effect shaders are fragment shaders. You can write your own and ship them in the chart package. In the shader field use /path/to/shader; the leading / is required to distinguish custom from built-in shaders.

Use GLSL 1.00 for compatibility.

Built-in variables

prpr provides:

varying vec2 uv; // texture UV
uniform vec2 screenSize; // screen size (full screen, not just chart area)
uniform sampler2D screenTexture; // screen texture (full screen)
uniform float time; // chart time in seconds

These exist but are not meaningful in the fragment shader; avoid reusing their names:

uniform mat4 Model;
uniform mat4 Projection;
uniform vec2 UVScale;

Shader parameters

To expose parameters from the chart, define uniforms like:

uniform type name; // %def%

type is the type (float, vec2, vec4 supported); name is the name; def is the default. All three are required.

Example

This example tints the screen red according to factor:

#version 100
precision mediump float;

varying lowp vec2 uv;
uniform sampler2D screenTexture;

uniform float factor; // %0.5% 0..1

void main() {
  gl_FragColor = mix(texture2D(screenTexture, uv), vec4(1.0, 0.0, 0.0, 1.0), factor);
}