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XDRV Charting Guide

Helper Function Heap

As discussed in Lua: Abridged for XDRV, helper functions can make programming mods in XDRV a lot easier and much more succinct. If you have one or two functions that are generally useful for a lot of modfiles, you may find yourself copying and pasting the functions from file to file. If you don’t have any functions like that yet, maybe you’ll be able to find one here!

This page contains several helper functions by various XDRV charters. All helper functions in the repository can be viewed as separate files on this page. If you would prefer to read these helper functions from the GitHub itself, you can do so by going to the code directory of the GitHub repository. I recommend looking at the all.lua file in each subdirectory, which combines all functions and function documentation from the individual files in that folder.

Pulse Functions

Section titled “Pulse Functions”

Author: TheBlockiest

Events Alpha

These functions create a “pulse” effect in the background, increasing the background’s alpha value to one value, holding it for some (or no) time, and then decreasing it to another value. Pulses can be great for representing percussive elements like kicks, snares, and crashes. These pulse function use linear easing for alpha only.

pulse.lua
--[[
pulse(pulseAlpha, endAlpha, startBeat, beatDurations)
Pulses the lighting of the background by increasing and decreasing PathAlpha


Parameters:
- pulseAlpha: The alpha value of the peak of the pulse
- endAlpha: The alpha value of the end of the pulse
- startBeat: The beat to start the pulse on
- beatDurations: A table of three duration values: {inDuration, holdDuration, outDuration}
  - Over inDuration, the alpha eases from its last set value to pulseAlpha
  - Over holdDuration, the alpha stays at pulseAlpha
  - Over outDuration, the alpha eases from pulseAlpha to endAlpha
  - All duration values are stored in beats
]]
local function pulse(pulseAlpha, endAlpha, startBeat, beatDurations)
  local inDuration = beatDurations[1]
  local holdDuration = beatDurations[2]
  local outDuration = beatDurations[3]


  if inDuration == 0 then
    xdrv.RunEvent("SetPathAlpha","beat",startBeat,pulseAlpha)
  else
    xdrv.RunEvent("EasePathAlpha","beat",startBeat,pulseAlpha,inDuration)
  end


  local outStartBeat = startBeat + inDuration + holdDuration


  xdrv.RunEvent("EasePathAlpha","beat",outStartBeat,endAlpha, outDuration)
end


pulse(0.9,0.3,12,{0.25,0,0.75})

Split Alpha Functions

Section titled “Split Alpha Functions”

Author: TheBlockiest

Events Alpha

These functions swap the values of PathAlpha with the values of LeftPathAlpha and RightPathAlpha. This allows you to seamlessly swap whether alpha values are controlled together or individually.

splitAlpha.lua
--[[
splitAlpha(beat, alpha)
Sets PathAlpha to 1
Also sets the alpha of the left and right sides to a given value
Ensures that LeftPathAlpha and RightPathAlpha are not blended with PathAlpha


Parameters:
- beat: The beat to split the background alphas at
- alpha: The alpha to set the left and right sides of the background to
]]
local function splitAlpha(beat, alpha)
  xdrv.RunEvent("SetPathAlpha","beat",beat,1)


  xdrv.RunEvent("SetLeftPathAlpha","beat",beat,alpha)
  xdrv.RunEvent("SetRightPathAlpha","beat",beat,alpha)
end


splitAlpha(8,0.5)

Check Table Functions

Section titled “Check Table Functions”

Author: TheBlockiest

Data

These functions check for a value within a list (a sequentially & numerically-indexed table) or a table (any table). This functions can be useful if you want to exclude specific beats from a repeated mod.

checkList.lua
--[[
checkList(elt, list)
Checks if an element is within a list
Not guaranteed to work with non-list tables


Parameters:
- elt: The element to check the list for
- list: A numerically and sequentially indexed table
    - Ex. {4,11,2,0.5}


Returns:
- true if the element is found in the list
- false otherwise
]]
local function checkList(elt, list)
    for _, v in ipairs(list) do
        if v == elt then
            return true
        end
    end
    return false
end


local list = {1,3,4,6}
local hasElt = checkList(3,list)
-- hasElt = true
local hasElt2 = checkList(5,list)
-- hasElt2 = false

That’s all the helper functions I can compile so far, but I hope to add more in the future. Remember, take any helper functions from this repository that you wish to use.