Resources
Numerical accuracy
The calculations in our apps: the policy each one is under, the precision it runs at, and the code itself.
Calculation policies
A policy says how one family of calculations keeps its precision. Open one to see its calculations, by source file, and their code.
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3D check view exported as glTF
Writes the 3D check view to a binary glTF file in meters.
- TakeoffCraft
- 4 calculations
32-bit in part Open item -
3D finishing toolpaths
Finds the height of the tool tip over the part for parallel and scallop finishing, and the spacing of passes for a given cusp height.
- PartCraft
- 14 calculations
32-bit in part Open item -
3D site export (GLB, OBJ, USD) and the 3D pointer readout
Writes the 3D site as a GLB, OBJ or USD file, and shows the easting, northing and elevation under the pointer in the 3D view.
- CivilCraft
- 7 calculations in 4 files
32-bit in part Open item -
3D text
Makes letters as flat faces or as solids of a given depth from the stroke font and a pen width.
- ModelCraft
- 2 calculations
32-bit in part Open item -
Advanced simulation add-on: finding contact pairs
Finds flat faces of two separate pieces that face each other within a gap, as candidate contact pairs.
- PartCraft
- 2 calculations
32-bit in part Open item -
Annotations and scales read from a PDF
Turns the annotations of an opened PDF into editable markups (boxes, lines, outlines, pen strokes, count marks, text boxes) and reads the sheet's scale.
- MarkupCraft
- 10 calculations in 2 files
32-bit in part Open item -
Assembly drawing sheet and mesh exports
Lays out the assembly drawing (view scale, positions on the sheet, bill of materials masses) and writes the placed assembly as one mesh for STL or as a 3MF file.
- PartCraft
- 5 calculations
32-bit in part Open item -
Assistant and window read-outs of radio link and coverage
The numbers the assistant tools return for radio links and coverage, and the coverage read-out in the geotechnical and telecom window.
- CivilCraft
- 4 calculations in 2 files
32-bit in part Open item -
Assistant answers: what is above an element
Lists the elements whose bounding box starts within a distance above an element's top and overlaps its footprint, nearest first, with the gap in meters.
- BimCraft
- 1 calculation
32-bit in part Open item -
Automatic count by symbol matching
Finds every copy of a boxed symbol on the sheets by comparing pictures, so the copies can be counted.
- TakeoffCraft
- 15 calculations in 4 files
32-bit in part Open item -
Best route across the terrain
Finds the least-cost path between two points on the ground within a steepest grade and a tightest curve, and reports its length, steepest grade, smallest radius and earthwork.
- CivilCraft
- 5 calculations
32-bit in part Open item -
Boolean modifier
Unites, subtracts or intersects the mesh with another object and returns the result as a new mesh.
- ModelCraft
- 2 calculations
32-bit in part Open item -
Burn levels of an engraved picture
Resamples a gray picture to the engraving grid and turns each cell into a burn level.
- CadCraft
- PartCraft
- 2 calculations
32-bit in part Open item -
Clash check
Finds pairs of elements whose surfaces run into each other and reports how deep their boxes overlap.
- BimCraft
- 5 calculations
32-bit in part Open item -
Contact and magnet study results
Gathers the results of a contact study between parts and of a 2-D magnet study: maximum stress, displacement and flux density, contact force, and the per-vertex and per-element fields.
- PartCraft
- 10 calculations
32-bit in part Open item -
CraftScript number type conversions
The script functions that convert values to single precision or to whole-number types.
- PartCraft
- 2 calculations
32-bit in part Open item -
Distance grid: baking, sampling and volume
Stores a shape as signed distances on a sparse voxel lattice, built from a formula or from a closed triangle mesh, and reads values, gradients and the enclosed volume back from it.
- PartCraft
- 14 calculations in 4 files
32-bit in part Open item -
Draft and curvature analysis
Works out the draft angle of each face corner against a pull direction, the areas that pass or need draft, and the curvature limit shown with the curvature colors.
- PartCraft
- 3 calculations
32-bit in part Open item -
Drawing section view of a faceted part
Cuts the faceted solid with the section plane and draws what is behind it, with the cut outline.
- PartCraft
- 1 calculation
32-bit in part Open item -
Element triangles for analysis
Hands the placed triangles of an IFC element, in the file's coordinates and length unit, to the daylight, solar, embodied-carbon, library and placement code.
- BimCraft
- 1 calculation
32-bit in part Open item -
Exact solid: mesh, volume, area and tables
Produces the triangle mesh of the exact solid used for the view, STL and 3MF export and assembly checks, and reads its volume, surface area, face areas and edge lengths from the kernel.
- PartCraft
- 9 calculations
32-bit in part Open item -
Export to glTF and STL
The vertex coordinates and placement matrices written when a model is exported as a binary glTF (.glb) or a binary STL file.
- CadCraft
- ModelCraft
- 4 calculations
32-bit in part Open item -
Field builtins for scripts
Lets a script build implicit shapes, sample them, turn them into a body, measure its volume and check it for manufacturing.
- PartCraft
- 6 calculations
32-bit in part Open item -
Fillet, chamfer, draft, thread and mesh bodies on the mesh kernel
Builds rounds, bevels, drafted faces, threads and imported mesh bodies from the body as it is at that point in the history.
- PartCraft
- 9 calculations
32-bit in part Open item -
Floats read from USD files
Reads numbers from .usda and .usdc files, in the type each value is stored as.
- CadCraft
- BimCraft
- ModelCraft
- TakeoffCraft
- CivilCraft
- DetailCraft
- PartCraft
- 5 calculations in 2 files
32-bit in part Open item -
Flow study: 32-bit steps in the mesh and the result fields
The largest speed, the pressure range, the values under the result probe and the surface pressure of a flow study, and the mesh the study is built from.
- PartCraft
- 5 calculations in 3 files
32-bit in part Open item -
Flow study: turbulence model and wall functions
Adds an eddy viscosity to the flow solver and sets the wall shear from a wall law, for turbulent runs marked experimental.
- PartCraft
- 10 calculations
32-bit in part Open item -
Focus distance picked in the view
The focus distance set by clicking a point in the live rendered view.
- BimCraft
- ModelCraft
- 1 calculation
32-bit in part Open item -
Generated part exports: data sheet, VTK, 3MF and OpenVDB
Writes a generated part's field and surface to VTK, 3MF and OpenVDB files and its values to a data sheet.
- PartCraft
- 8 calculations in 2 files
32-bit in part Open item -
Generative design by topology optimization
Finds which part of a design space to keep for the stiffest shape at a given volume, turns the result into a solid design and a surface mesh, and checks its mass, stress and displacement.
- PartCraft
- 15 calculations
32-bit in part Open item -
Geometric room acoustics
Works out how sound energy arrives at a listener over time in a room, by image sources or by ray tracing, and from that the reverberation and clarity measures per octave band.
- BimCraft
- 6 calculations
32-bit in part Open item -
glTF import: meshes, skins and placements
Turns a read glTF scene into mesh definitions and placements with Z up: welds vertices, applies skins and morph weights, drops empty triangles and marks sharp edges.
- ModelCraft
- 9 calculations
32-bit in part Open item -
Ground read from a survey file
Reads ground points from a points file, drawing contours, a LAS or LAZ cloud, an elevation grid or LandXML, and sets their unit, offset and datum before they become the site's ground.
- BimCraft
- 4 calculations
32-bit in part Open item -
Half floats in EXR
Converts between 16-bit half floats and 32-bit floats for EXR channels.
- BimCraft
- ModelCraft
- 2 calculations
32-bit in part Open item -
Half floats in USD
Converts between 16-bit half floats and 32-bit floats for USD half types.
- CadCraft
- BimCraft
- ModelCraft
- TakeoffCraft
- CivilCraft
- DetailCraft
- PartCraft
- 2 calculations
32-bit in part Open item -
Headset review: measuring, section cuts and issue cameras
Works out the distance between two points picked in a headset, the plane of a section cut made there, and the camera and place saved with an issue.
- BimCraft
- ModelCraft
- 9 calculations in 2 files
32-bit in part Open item -
Hollowing a body to a wall thickness
Makes the inside surface that leaves a wall of the asked thickness, reports the volume taken out, and builds drain holes through the wall.
- ModelCraft
- 8 calculations
32-bit in part Open item -
Hours of direct sun on the ground and on walls
Counts the hours of direct sun each ground cell and each wall point of the building masses gets on chosen days, with the masses and the terrain casting shadows.
- CivilCraft
- 9 calculations
32-bit in part Open item -
Hull hydrostatics and righting arms
Works out a floating part's displaced volume, displacement, centers of buoyancy and flotation, metacentric heights and the righting-arm curve at a given draft.
- PartCraft
- 5 calculations
32-bit in part Open item -
IFC export of parts, assemblies and library items
Writes the mesh, placements, quantities and parameter values of a part, an assembly or a library item into an IFC4 file.
- PartCraft
- 6 calculations
32-bit in part Open item -
IFC geometry handed to the apps
Gives each app an element's triangles and the matrix that places them, in meters with Y up, moved near the origin.
- BimCraft
- TakeoffCraft
- CivilCraft
- DetailCraft
- 4 calculations
32-bit in part Open item -
IFC openings, clippings and half-space cuts
Cuts openings and clipping solids out of an IFC element's mesh, so the element is drawn and measured with its voids.
- BimCraft
- TakeoffCraft
- CivilCraft
- DetailCraft
- 8 calculations
32-bit in part Open item -
Import of a parametric export file
Rebuilds a part feature by feature from a cadcraft-sw-export file: sketches moved into the part's planes, edges and faces found from their positions, parameters and equations carried over, and the volume compared with the one in the file.
- PartCraft
- 11 calculations
32-bit in part Open item -
Interference between assembly parts
Finds pairs of placed parts that overlap, with the overlapping volume, and steps a joint through a range to check for clashes along the way.
- PartCraft
- 3 calculations
32-bit in part Open item -
Library items from IFC types
Turns an IFC type or element into a library item: its body mesh, its width, depth and height, its plan outline and its sizes from properties, in millimeters.
- BimCraft
- 4 calculations
32-bit in part Open item -
Magnetics add-on: field readout, flux lines and exports
Works out each body's area and mean and peak flux density, compares the result with a hand formula, traces flux lines and writes CSV and VTK files.
- PartCraft
- 9 calculations
32-bit in part Open item -
Manual: imported product meshes, copies and part volume
Reads a product from glTF, OBJ, STL or 3MF into a manual, scales it to millimeters, recognizes copies of one part and works out each part's volume and area.
- PartCraft
- 13 calculations in 2 files
32-bit in part Open item -
Material maps and statistics from a photo
Makes the color, roughness and normal maps of a tiling material from one photo, and reports how visible the tile's join is and how much relief the photo has.
- BimCraft
- ModelCraft
- 4 calculations
32-bit in part Open item -
MaterialX files: numbers written and read
Writes a material's parameters, tile size and displacement to a MaterialX file, and reads them back from one.
- BimCraft
- ModelCraft
- 9 calculations in 2 files
32-bit in part Open item
A policy is added only after its source was read. Each statement can be checked in the code shown on its page; the app repositories are public. When a release changes a calculation, its page says so until it has been read again.
The standard
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64-bit everywhere
Every calculation runs in 64-bit floating point (IEEE 754 double precision), from the number you type to the number you read.
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15 digits, always
A 64-bit number keeps any 15-digit value intact and takes 17 digits to write out in full. Our rule for every calculation: carry all 17 between steps, and order the arithmetic so that avoidable rounding never costs one of the first 15.
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32-bit gets a warning
A 32-bit number keeps about 7 digits. Where a 32-bit step can reach a number you read, the calculation is flagged in the lists below, and the app will warn that the result can have less mathematical precision.
This device
What this browser can see of your machine. It is shown here only and sent nowhere; the desktop app reads the full hardware, a web page cannot.
The apps calculate in 64-bit on every device. Work handed to the graphics processor is the exception: browsers expose graphics processors as 32-bit calculators, which can provide less mathematical precision.
- Processor
- Memory
- Numbers in the apps
- Graphics processor (WebGL)
- WebGPU
A browser reports a rounded or capped view of the machine, never a full inventory: it gives the number of processor threads (not the model), memory rounded down and capped at 8 GB (Chromium only), and one graphics adapter even when a machine has several. What the browser reports about graphics is a capability, not a measurement of the card. The size of a graphics card's memory bus (a 192-bit bus, for example) says how fast data moves, not how precisely it calculates. Most graphics cards can calculate in 64-bit natively, slowly, but WebGL and WebGPU do not offer it to web pages.
Approaches
Every policy takes one of five approaches to keeping its precision.
- Exact values 8 policies
- Constants and factors are held as exact fractions from their definitions. The arithmetic is ordered so that no rounded factor is ever used.
- Exact predicates 1 policy
- Coordinates are 64-bit. The yes-or-no decisions that shape the geometry (which side of a line, inside or outside a circle) are computed exactly, so rounding cannot flip one.
- 64-bit, direct 337 policies
- Every value is a 64-bit number from input to result. Formulas are closed form or a direct solve, and every comparison uses a stated tolerance.
- 64-bit, stated limit 428 policies
- The arithmetic is 64-bit, but the method or the data sets the accuracy: a solver tolerance, a mesh, a step size, a datum shift, a table. The limit is stated where the result is shown.
- Display only 49 policies
- Computed to draw the screen, often in 32-bit on the graphics processor. No number a person reads, saves or exports comes from it.
- 32-bit step, flagged 118 policies
- One step stores or exchanges 32-bit values that reach a number a person reads. It is listed here with its open item, and the step is either moved to 64-bit or the app will warn where the number is read.
Precision is not robustness
Mathematical precision is how many digits a number keeps. Geometric robustness is whether a shape stays valid: every intersection found, every solid closed, every face joined to its neighbors. They are different properties, and a CAD system can have the first without the second.
Every geometric algorithm rests on yes-or-no questions. Is this point left or right of that line? Do these two edges cross? Is this point inside that circle? Each answer is the sign of a small expression. When three points are almost in line, the true value of that expression can be smaller than the rounding error of the arithmetic that computes it, and the sign comes out wrong. That happens at 15 digits as readily as at 7.
One wrong sign is not a small error in the last digit. It is a different decision: an intersection that is missed, two triangles that overlap, a face that points the wrong way, a solid with a gap in it. Every coordinate can be correct to 15 digits while the shape they describe is invalid.
What makes geometry robust
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Exact predicates
The yes-or-no questions are answered exactly. The fast 64-bit answer is used when it is safely away from zero. When it is not, the sign is computed again with as many digits as it takes.
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Decide once
A decision about a shape is recorded as topology, and every later step agrees with it. The same question is never asked twice with a chance of two answers.
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Stated tolerances
Where a tolerance is used it is written down, scaled to the size of the geometry and applied the same way everywhere.
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Local origins
Coordinates far from zero are moved to a local origin before the work, so the digits are spent on the geometry and not on the distance to the origin.
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Valid by construction
Algorithms whose result is guaranteed to be a closed solid, whatever the input, in place of ones that repair the result afterwards.
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More than the language
These choices matter more than the programming language. JavaScript, C++ and Rust all compute with the same 64-bit numbers: the same algorithm is as robust, or as fragile, in each.
Where our apps stand
The list on this page records both properties. Surface triangulation in CivilCraft and BimCraft uses exact predicates. Solid modeling in PartCraft runs on a kernel whose result is a closed solid by construction. The intersections in the CadCraft app use stated tolerances today, and exact tests for the near-parallel and near-tangent cases are an open item. Each policy says which approach it takes.