Custom Shaders

Effect shaders are fragment shaders. You can write your own and include them in the chart package. In the shader field, use /path/to/shader; the leading / is required so custom shaders can be distinguished from built-in ones.

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 names also exist, but they are not meaningful in the fragment shader, so avoid reusing them:

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

Shader parameters

To expose chart-controlled parameters, define uniforms like this:

uniform type name; // %def%

Here, type is the type (float, vec2, and vec4 are supported), name is the uniform name, and def is the default value. 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);
}