VHSh

Video Home Shader: A demo tool for digitally assisted analog vjaying

Setup

Create a virtual environmenet and install the dependencies

python3.10 -m venv .venv
source .venv/bin/activate
pip3 install -r requirements.txt

Usage

Then run VHSh fron that environment

source .venv/bin/activate
python3 vhsh.py mandelbrot.glsl

If you pass multiple shader files, you can switch between them in the tool. To open all files in a given folder, use my_shader_folder/*.

You can pass --watch to automatically reload the shader upon file change.

To toggle the UI, press <tab>.

If you're seeing a message like

2024-10-02 22:10:15.567 Python[75271:1828570] ApplePersistenceIgnoreState: Existing state will not be touched. New state will be written to /var/folders/2b/gfpmffr15n9cwdy6_44mhy8r0000gn/T/org.python.python.savedState

run the following to get rid of it:

defaults write org.python.python ApplePersistenceIgnoreState NO

MIDI Support

When using the --midi flag, VHSh will listen to incoming MIDI messages and allow you to map parameters to MIDI controls. How to assign uniform mappings is described in Custom Parameters.

There are also a couple of system controls, like switching scenes, that can be mapped to buttons as well. Such a mapping is defined as a TOML file and passed via --midi-mapping.

[scene]
prev = 58  # switch to next scene
next = 59  # switch to previous scene

[preset]
prev = 61  # switch to next preset
next = 62  # switch to previous preset
save = 60  # save current parameter values to a new preset

[uniform]
toggle_ui = 45  # toggle paramter tweaking window

[uniform.time]
toggle = 41  # toggle u_Time running

Sensible mappings for various controls are supplied in midi_mappings/.

Writing Shaders for Video Home Shader

Video Home Shader supplies you with a 2D canvas to draw into using an OpenGL fragment shader. It is run once for every pixel on the screen and determines it's color.

Berfore your shader file is run, a preamble is prepended to the source code. It defines

OpenGL Version 330 core

so you just need to supply a main function and set the output color FragColor as an RGBA vec4 with floats between 0 and 1 (0., 0., 0., 1.) being black).

void main() {
    FragColor = vec4(0.8, 0.2, 0.2, 1.0);
}

Builtin Parameters

You can use the following built-in parameters, that are pre-defined in the preamble:

• vec2 u_Resolution: width and height of the window in pixels. This can be used to calculate normalized screen space coordinates like

  vec2 pos = gl_FragCoord.xy / u_Resolution;

  where pos.xy will now have the current pixel's coordinates between [-1, 1]^2
• float u_Time: Seconds since the program start. This can be used to animate things. For example

  vec4 color = vec4((sin(2. * 3.14 * u_Time * ) + 1.) / 2., 0., 0., 1.);

  will create a red pulsing effect with one pulse per second.

Custom Parameters

You can define custom parameters to vary directly in the code, and the user interface to manipulate them will be generated automatically. Use the uniform keyword followed by a type (bool, int, float, vec2, vec3, vec4) and a name.

uniform bool override_red; // =False
uniform int n_max; // =10 [1,200] #0
uniform float scale; // =1. [0.,2.] #16
uniform vec2 origin; // =(0.,0.) [-2.,-2.]
uniform vec3 dir; // =(1.,0.,0.) [-1.,-1.]
uniform vec4 base_color; // <color> =(1.,1.,0.,1.)

Using a special syntax in a comment on the same line, you can define the the following uniform control properties:

• =VALUE default value
• [MIN,MAX,STEP] range (where STEP is optional).
• <WIDGET> special UI widget
  • <color> on vec3 for a RGB and on vec4 for a RGBA color picker
  • <log> for a logarithmic scale
  • <drag> for controling the UI widget with dragging (instead of slider)
• #MIDI MIDI control ID. To bind a MIDI control to a uniform, for example: #16.

The have to be defined in the order

uniform type name; // <WIDGET> =VALUE [MIN,MAX,STEP] #MIDI

and the values (and ranges) may not contain whitespace. Each individual part (widget, value, range) is optional and they can be mixed and matched as desired, as long as the order of appearance is correct. As generally with GLSL, it is also important to strictly match the types. Supplying a float as default value for an int will not work. There may be no other text in the comment. All vector types have to be supplied as a comma-separated list of floats, enclosed by parentheses (1.,2.,3.). One can only supply a scalar range that applies along all dimensions.

// syntax error
uniform float scale; // =1
// OK
uniform float scale; // =1.

// syntax error
uniform vec2 origin; // =[0.,0.]
// OK
uniform vec2 origin; // =(0.,0.)

// syntax error
uniform vec3 dir; // [[0.,1.],[0.,1.],[0.,5.]]
// OK
uniform vec3 dir; // [0.,1.]
dir.z *= 5;

By using ctrl+click, one can directly edit the values with keyboard input.

If two consecutive uniforms share a common prefix in their name (like box_size and box_color), they will be grouped together.

Presets

You can save the current uniform values as the new =DEFAULT parameter in your loaded shader source file by clicking Save when the currently selected preset. is <current>.

Furthermore, you can store multiple sets of parameters (including different) default values, ranges, MIDI mappings etc.) as presets. To save a new preset, enter the name in the Name field and click New Preset. The shader source file will be modified by prepending the unform and metadata defintions with a special comment prefix (/// ). Since all those lines will deleted and rewritten on save, be sure to not use triple-slashes for other reasons. Each preset is preceeded by its name.

/// // My New Preset
/// uniform bool override_red; // =False
/// uniform int n_max; // =10 [1,200] #0
/// uniform float scale; // =1. [0.,2.] #16
/// uniform vec2 origin; // =(0.,0.) [-2.,-2.]
/// uniform vec3 dir; // =(1.,0.,0.) [-1.,-1.]
/// uniform vec4 base_color; // <color> =(1.,1.,0.,1.)

You can add, modify and delete these comment blocks with you're text editor as well.

To update an existing preset, select it, adjust the parameter values and click Save. The current paremeter values will be written to the default values of the currently selected preset.

TODO

• render fragment shader over the whole screen
• load shader from file
• auto-generate tuning ui for uniforms
• auto-define builtin uniforms / math library / preamble
• hot reload https://watchfiles.helpmanual.io/api/watch/
• define defaults and ranges in uniform definition as comment
• MIDI controller support
• select different shaders
• save and load different presets
• write current values to file
• 60fps cap / fps counter
• show or hide the controls
• imgui display shader compile errors
• widget size and close button
• re-parse metadata on reload
• remember window position
• fix t as uniform name doesn't generate ui
• bug uniform parsing when float =0.0
• limit resolution and upscale
• write state to MIDI controler (uTime, UI toggle etc)
• autosave and restore uniform values atexit and pickle
• #includes, or at least one stdlib in preamble, or pass libs
• vec3 input method: - select dim with S/M/R buttons, then use the slider - auto assign n sucessor ids as well - have the user assign multiple #1,#2,#3
• "touchpad" widget for vec2
• record mp4
• startup mode: no gui and fullscreen (not possible in glfw, need sdl) maybe glfw.get_cocoa_window glfw/glfw#1216
• widgets
  • <log>
  • <drag> drag input, others sliders (for slider flags)
  • ~~~<hsv and <rgb>~~~
  • MIDI vector control with button triplet
• uniforms
  • time
  • mouse
  • prev frame
  • audio fft
  • video in
• Gamma Correctio
  • Monitor Guide: Gamma ramp
  • GLFW_SRGB_CAPABLE
  • GLFWgammarramp
• big refactoring
  • one file? or full package with exe in PATH?
  • docstrings

  • VideoHomeShader
        context: all variables to consider
      MIDIManager
        Thread
        needs uniforms, system commands
      GUI
        needs uniforms, system commands
      ShaderRenderer
        scenes
        needs system commands
      FileWatcher
        talks to Shader Renderer
      PresetManager
        presets
    

• switch to SDL?
  • native macos fullscreen
  • mic input https://www.lazyfoo.net/tutorials/SDL/34_audio_recording/index.php

Resources

• https://pyopengl.sourceforge.net/documentation/manual-3.0/
• https://regex101.com
• https://github.com/pyimgui/pyimgui/blob/master/doc/examples/testwindow.py
• https://pthom.github.io/imgui_manual_online/manual/imgui_manual.html
• https://iquilezles.org/articles/
• https://docs.gl/sl4/
• https://www.youtube.com/watch?v=f4s1h2YETNY
• http://dev.thi.ng/gradients/
• https://mido.readthedocs.io/en/stable/intro.html