Shader #

Overview #

The Shader project type allows you to create visual effects by writing OpenGLES fragment shaders. Fragment shaders work by running your code once for each pixel on the screen, which allows for some super-cool graphical creations using code and maths. Pip’s camera is even supported too!

Example #

// param label="Red" default=1
uniform float red;

// param label="Green" default=1
uniform float green;

// param label="Blue" default=1
uniform float blue;

void main(void) {
    vec4 c = texture2D(camera, texCoord);
    c.x *= red;
    c.y *= green;
    c.z *= blue;
    gl_FragColor = c;
}

Built-in variables #

The following variables are automatically added to your code and are always available.

• texCoord: the texture coordinate currently being calculated
• gl_FragColor: output colour for the current texture coordinate
• camera: sampler2D containing realtime feed from Pip’s camera
• time: float representing the number of seconds since execution began
• millis: int representing number of milliseconds since execution began

Parameters #

It’s possible to add parameters to your Shader sketches and have Pip auto-generate sliders for tweaking their values in real-time. To do this, declare your parameters as GLSL uniform variables, give it a // param comment, and optionally add tags to customise how the slider should behave:

// param label="Red Level" min=0 max=1
uniform float red;

The code snippet above will create a slider labelled “Red Level” that modifies the variable red, restricted to values between 0 and 1. The complete list of support tags is:

• min: minimum value
• max: maximum value
• default: default value
• step: amount by which value changes
• label: text label to display beside slider

For bool variables, min is always 0, max is always 1, and step is always 1. int and uint variables have a default range of 0-100 with a default step of 1, and float variables have a default range of 0-1 with a step of 0.

The sliders’ on-screen visibility can be toggled by pressing Pip’s top-right shoulder button (Note: the controllers must be detached).