Resources Numerical accuracy

Calculations

Every calculation under our calculation policies: what it works out, its formula and the precision it runs at. Open one to see its code as it is in the released app.

  • 6,917 calculations in 1,248 source files
  • 143 exact
  • 6,286 in 64-bit
  • 335 with a 32-bit step
  • Last reviewed

Calculations

  • Rounding of a slider value

    Removes binary noise such as 0.30000000000000004 from a slider's value.

    v = round to (decimals of the step + 2) decimals, at most 8

    Numbers typed into the property grid app-propgrid.js Every app
    64-bit
  • Value of a slider row

    The number handed to the app while a slider is dragged or its box is changed.

    v = fix(clamp(value, min, max), step)

    Numbers typed into the property grid app-propgrid.js Every app
    64-bit
  • Integer or float

    Decides how a number is written.

    Numbers sent between people editing together live-client.js Every app
    64-bit
  • Writing a float

    Writes a number as 8 bytes.

    Numbers sent between people editing together live-client.js Every app
    64-bit
  • Writing an integer

    Writes a whole number in the shortest integer form that holds it.

    Numbers sent between people editing together live-client.js Every app
    Exact
  • Reading a float

    Reads a 4-byte or an 8-byte float from a message.

    Numbers sent between people editing together live-client.js Every app
    64-bit
  • Reading a 64-bit integer

    Reads an unsigned or signed 64-bit integer.

    Numbers sent between people editing together live-client.js Every app
    Exact
  • Cost of one call

    The cost of a call from its token counts and the model's prices.

    cost = (in × price in + out × price out) ÷ 1,000,000

    Spending on a person's own AI model ai-byok.js Every app
    64-bit
  • Spending today and this month

    The cost, tokens and number of calls for the current day and month, and the calls in the last hour.

    amount = Σ cost of the calls in the period

    Spending on a person's own AI model ai-byok.js Every app
    64-bit
  • Check before a call

    Refuses a call when the calls per hour, the day's or month's spending, or the day's tokens could pass a limit.

    refuse when spent + worst-case cost > limit; worst case = cost(estimated input, largest allowed output)

    Spending on a person's own AI model ai-byok.js Every app
    64-bit
  • Recorded cost and the token estimate

    Stores each call's cost and estimates the input tokens of the next request.

    estimated tokens = ⌈JSON length ÷ 3⌉ + 500

    Spending on a person's own AI model ai-byok.js Every app
    64-bit
  • Flow through a passage

    Persons per second through a door or corridor of a given width.

    rate = max(0, Fsm × (width − 2 × boundary))

    People flow and evacuation time people.js Every app
    64-bit
  • Speed and specific flow at a density

    Walking speed and flow per meter of width at a given density of people.

    S = k × (1 − 0.266 × D); Fs = S × D; k = 1.4 m/s

    People flow and evacuation time people.js Every app
    64-bit
  • Rate and speed of each passage

    The flow rate and walking speed each passage gets, from its own values or the defaults for its kind.

    People flow and evacuation time people.js Every app
    64-bit
  • Door service time and walking time

    How long a door takes per person, how long the passage takes to walk, and each room's distance to an exit in time.

    service = 1 ÷ rate; walk = length ÷ speed; to exit = least total walking time

    People flow and evacuation time people.js Every app
    64-bit
  • Which way a room empties

    The next passage for people in a room: the one with the least remaining walking time to an exit.

    keep a hop when toExit(next) < toExit(room) − 1e-9; choose the least walk + toExit(next)

    People flow and evacuation time people.js Every app
    64-bit
  • Evacuation results

    People evacuated, the time the last person reaches an exit, peak occupancy and density per room, and queues per door.

    time = latest arrival at any exit; density = peak people in a room ÷ its area

    People flow and evacuation time people.js Every app
    64-bit
  • Joint frames at a pose

    Each joint's rotation and offset from its parent at the given joint values.

    Rigid-body dynamics of a mechanism dynamics.js Every app
    64-bit
  • Joint torques for a motion (inverse dynamics)

    The torque or force each joint needs for given positions, velocities and accelerations, with gravity, external loads and damping.

    outward: ω, α, a of each link; F = m × a_com; N = I α + ω × (I ω); inward: τᵢ = axis · n (revolute) or axis · f (prismatic) + damping × q̇ᵢ

    Rigid-body dynamics of a mechanism dynamics.js Every app
    64-bit
  • Mass matrix

    The joint-space mass matrix at a pose.

    column j = rnea(q, q̇ = 0, q̈ = unit vector j) with no gravity, damping or external loads

    Rigid-body dynamics of a mechanism dynamics.js Every app
    64-bit
  • Joint accelerations for given torques (forward dynamics)

    The acceleration of each joint under applied torques.

    M q̈ = τ − h

    Rigid-body dynamics of a mechanism dynamics.js Every app
    64-bit
  • Kinetic and potential energy

    The mechanism's kinetic, potential and total energy at a pose and velocity.

    KE = ½ q̇ᵀ M q̇; PE = −Σ m × (g · p_com)

    Rigid-body dynamics of a mechanism dynamics.js Every app
    64-bit
  • Simulated motion over time

    Joint positions and velocities at each time step under gravity and applied torques.

    RK4: y₊ = y + dt ÷ 6 × (k₁ + 2k₂ + 2k₃ + k₄); steps = round(T ÷ dt); t = step × dt

    Rigid-body dynamics of a mechanism dynamics.js Every app
    64-bit
  • Courtyard of a footprint

    The rectangle around all pads, grown by a margin.

    courtyard = (min(x − w ÷ 2) − m, min(y − h ÷ 2) − m, max(x + w ÷ 2) + m, max(y + h ÷ 2) + m)

    Parametric PCB footprints footlib.js Every app
    64-bit
  • Two-terminal chip

    Two pads at half the pitch either side of the center.

    x = ∓ pitch ÷ 2

    Parametric PCB footprints footlib.js Every app
    64-bit
  • Dual-row surface-mount package

    Pads in two rows, numbered counter-clockwise from the top left.

    y = ((n ÷ 2 − 1) ÷ 2 − i) × pitch; x = ∓ row spacing ÷ 2

    Parametric PCB footprints footlib.js Every app
    64-bit
  • Dual in-line through-hole package

    Drilled pads in two rows.

    y = ((n ÷ 2 − 1) ÷ 2 − i) × pitch; x = ∓ row spacing ÷ 2

    Parametric PCB footprints footlib.js Every app
    64-bit
  • Pin header

    Drilled pads in one or two rows at a pitch.

    x = (r − (rows − 1) ÷ 2) × pitch; y = ((n − 1) ÷ 2 − i) × pitch

    Parametric PCB footprints footlib.js Every app
    64-bit
  • Quad flat package

    Pads on four sides, numbered counter-clockwise from the top left.

    along a side: ((n − 1) ÷ 2 − i) × pitch; across: ± span ÷ 2

    Parametric PCB footprints footlib.js Every app
    64-bit
  • Axial through-hole part

    Two drilled pads at half the lead pitch either side of the center.

    x = ∓ pitch ÷ 2

    Parametric PCB footprints footlib.js Every app
    64-bit
  • Meets the limit

    True, false or null for a found value against a rule.

    min − e ≤ found ≤ max + e

    Pass or fail against a regulation limit addons/regs/lib/rows.js
    • CadCraft
    • BimCraft
    • CivilCraft
    • DetailCraft
    64-bit
  • Ring orientation

    The signed area that decides if a ring runs counter-clockwise.

    A = ½ Σ (xᵢ·yᵢ₊₁ − xᵢ₊₁·yᵢ)

    Polygon triangulation by ear clipping ifc/geo-tri.js
    • BimCraft
    • TakeoffCraft
    • CivilCraft
    • DetailCraft
    64-bit
  • Cross product and inside test

    Which side of a line a point lies on and whether a point is inside a triangle.

    cross = (bx−ax)(cy−ay) − (by−ay)(cx−ax)

    Polygon triangulation by ear clipping ifc/geo-tri.js
    • BimCraft
    • TakeoffCraft
    • CivilCraft
    • DetailCraft
    64-bit
  • Hole bridge

    The vertex of the outer ring a hole is joined to.

    Polygon triangulation by ear clipping ifc/geo-tri.js
    • BimCraft
    • TakeoffCraft
    • CivilCraft
    • DetailCraft
    64-bit
  • Ear test

    Whether a corner can be cut off as a triangle.

    Polygon triangulation by ear clipping ifc/geo-tri.js
    • BimCraft
    • TakeoffCraft
    • CivilCraft
    • DetailCraft
    64-bit
  • Triangulate rings on a plane

    The triangles of 3D rings that lie on one plane.

    Polygon triangulation by ear clipping ifc/geo-tri.js
    • BimCraft
    • TakeoffCraft
    • CivilCraft
    • DetailCraft
    64-bit
  • Vertices and loose edges

    The point positions of a model definition and its loose edges.

    Model points written to USD usd/m3d.js
    • CadCraft
    • BimCraft
    • ModelCraft
    • TakeoffCraft
    • CivilCraft
    • DetailCraft
    • PartCraft
    32-bit in part
  • Mesh arrays

    The point, normal, UV and color arrays of a mesh.

    Model points written to USD usd/m3d.js
    • CadCraft
    • BimCraft
    • ModelCraft
    • TakeoffCraft
    • CivilCraft
    • DetailCraft
    • PartCraft
    32-bit in part
  • Number to text

    The text a number is written as, by type.

    f32: text = shortest s with fround(+s) = fround(x)

    Number text in USD files usd/usda-write.js
    • CadCraft
    • BimCraft
    • ModelCraft
    • TakeoffCraft
    • CivilCraft
    • DetailCraft
    • PartCraft
    32-bit in part
  • Shortest digits

    A number to p significant digits without trailing zeros.

    Number text in USD files usd/usda-write.js
    • CadCraft
    • BimCraft
    • ModelCraft
    • TakeoffCraft
    • CivilCraft
    • DetailCraft
    • PartCraft
    64-bit
  • Type name to number type

    Which number type a USD type name uses (32-bit float, half or 64-bit double).

    Number text in USD files usd/sdf.js
    • CadCraft
    • BimCraft
    • ModelCraft
    • TakeoffCraft
    • CivilCraft
    • DetailCraft
    • PartCraft
    Exact
  • Inline values

    A value that the file stores inside its 32-bit payload word.

    Floats read from USD files usd/usdc-read.js
    • CadCraft
    • BimCraft
    • ModelCraft
    • TakeoffCraft
    • CivilCraft
    • DetailCraft
    • PartCraft
    32-bit in part
  • Raw arrays

    A packed array of numbers of one type.

    Floats read from USD files usd/usdc-read.js
    • CadCraft
    • BimCraft
    • ModelCraft
    • TakeoffCraft
    • CivilCraft
    • DetailCraft
    • PartCraft
    32-bit in part
  • Compressed float arrays

    An array stored as whole numbers or as a lookup table and indexes.

    Floats read from USD files usd/usdc-read.js
    • CadCraft
    • BimCraft
    • ModelCraft
    • TakeoffCraft
    • CivilCraft
    • DetailCraft
    • PartCraft
    32-bit in part
  • Float text rounding

    A float or half value read from .usda text.

    Floats read from USD files usd/usda-read.js
    • CadCraft
    • BimCraft
    • ModelCraft
    • TakeoffCraft
    • CivilCraft
    • DetailCraft
    • PartCraft
    32-bit in part
  • Arrays from text

    A list of parsed numbers as a typed array of the right type.

    Floats read from USD files usd/usda-read.js
    • CadCraft
    • BimCraft
    • ModelCraft
    • TakeoffCraft
    • CivilCraft
    • DetailCraft
    • PartCraft
    32-bit in part
  • Half to float

    The value of a 16-bit half float.

    v = ± (1 + m ÷ 1024) × 2^(e − 15)

    Half floats in USD usd/util.js
    • CadCraft
    • BimCraft
    • ModelCraft
    • TakeoffCraft
    • CivilCraft
    • DetailCraft
    • PartCraft
    32-bit in part
  • Float to half

    The 16-bit half closest to a number.

    Half floats in USD usd/util.js
    • CadCraft
    • BimCraft
    • ModelCraft
    • TakeoffCraft
    • CivilCraft
    • DetailCraft
    • PartCraft
    32-bit in part
  • Measure to SI

    A property value in meters, square meters or cubic meters.

    area = v × L²; volume = v × L³

    IFC measures in SI for USD usd/ifc.js
    • CadCraft
    • BimCraft
    • ModelCraft
    • TakeoffCraft
    • CivilCraft
    • DetailCraft
    • PartCraft
    64-bit
  • Depth, volume and flow unit factors

    Converts the solver's meters, cubic meters and cubic meters per second to the units the window shows.

    mm = m × 1000; in = m × 39.3700787; yd³ = m³ ÷ 0.028316846592 ÷ 27; ft³/s = m³/s ÷ 0.028316846592

    Rainfall run read-outs: deepest water and depth scale rain-ui.js
    • CivilCraft
    64-bit

A calculation is added only after its source was read. Each statement can be checked in the code shown on its policy's page; the app repositories are public. When a release changes a calculation, its page says so until it has been read again.