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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2D constraint solver
Moves lines, circles, arcs, points and polyline vertices so that the geometric and dimensional constraints placed on them are met.
- CadCraft
- 9 calculations
64-bit Open item -
2D flow solver (finite volume)
Computes laminar flow in a rectangular region and the mixing of a tracer in it: velocities, pressure, concentration and a mixing time.
- CadCraft
- 14 calculations
64-bit Open item -
2D mixing solver (lattice Boltzmann)
Computes laminar flow and tracer mixing in tanks and flow-through boxes on a lattice, with a mixing time and a residence time distribution.
- CadCraft
- 10 calculations
64-bit Open item -
3D solid commands: sizes, paths and reported volume
Turns the heights, angles, outlines and paths typed or picked for EXTRUDE, SWEEP and REVOLVE into the numbers the solid is built from, and works out the volume the command line prints.
- CadCraft
- 5 calculations
64-bit -
3D solids, faces and units in a drawing
Builds boxes, cylinders, wedges and extrusions from 2D outlines, reports their volume, and carries the 3D model between drawing units and meters.
- CadCraft
- 9 calculations
64-bit -
3DM import: units, placements and mesh points
Brings the meshes, curves and block placements of a .3dm file into the model in meters.
- ModelCraft
- PartCraft
- 5 calculations in 2 files
64-bit -
3DM surfaces into triangles
Turns the trimmed surfaces and extrusions of a .3dm file into triangle meshes, or uses the render mesh the file saved.
- ModelCraft
- PartCraft
- 10 calculations in 2 files
64-bit -
ACIS solids turned into triangles
Turns the 3D solids stored in DWG and DXF files (ACIS data) into triangle meshes: shown on CadCraft's 3D tab, and brought into ModelCraft as groups when such a file is imported.
- CadCraft
- ModelCraft
- 26 calculations in 2 files
64-bit Open item -
Activated sludge plant steady state (ASM1)
Works out the steady concentrations in a chain of treatment tanks with recycles and a clarifier, the effluent and waste sludge, the sludge age and the mass balances.
- CadCraft
- BimCraft
- 8 calculations
64-bit Open item -
Adaptive clearing passes
Plans roughing passes that keep the cutter's sideways engagement near a set width, and re-checks the engagement they give.
- PartCraft
- 9 calculations
64-bit -
Add-on display bodies: stored coordinates and placement
Checks the boxes and meshes an add-on places in the view, stores them in the part file, and places them in the world.
- PartCraft
- 4 calculations
64-bit Open item -
Address to site: parcel area, distances and shares
For a point and a set of open-data layers, works out the parcel's area, the distance to nearby buildings and the share of the parcel in each zoning district, soil unit and flood zone.
- CivilCraft
- 6 calculations
64-bit Open item -
Alembic import
Reads meshes and their transforms from an Alembic cache and brings them in with Z up.
- ModelCraft
- 8 calculations
64-bit -
Analytical frame model from the drawn members
Turns the drawn beams, columns and braces into the nodes, members, sections, supports and loads the frame solver works on.
- DetailCraft
- 8 calculations
64-bit -
Animation keys, curves and poses
Where the camera and every moving object are at a given time of an animation, and the value of every animated property.
- BimCraft
- ModelCraft
- PartCraft
- 23 calculations
64-bit -
Apparel commands: piece table, marks and marker output
The Apparel add-on's commands that put numbers into the drawing or a file: the piece table, grain lines and buttonholes, automatic nesting on a marker and the marker's PDF.
- CadCraft
- 11 calculations
64-bit Open item -
AR on site: lining the model up with the building
Fits the model to the real site from two reference points pointed at with a phone, and checks that fit on a later visit.
- BimCraft
- ModelCraft
- 4 calculations in 2 files
64-bit -
Arcs, circles, smooth curves, divide and offset
The corner points of arcs, circles, polygons and smooth curves, what is reported about a curve, equal division, and the offset of a face outline or a chain of edges.
- CadCraft
- ModelCraft
- 11 calculations
64-bit Open item -
Automatic mesh refinement of tetrahedral studies
Decides which elements to refine after a solve, how small to make them, refines the mesh and stops when the estimated error meets the target.
- PartCraft
- 5 calculations
64-bit -
Average daylight factor of rooms
Works out each room's average daylight factor from its windows, its inside surfaces and the angle of sky each window sees.
- BimCraft
- 13 calculations
64-bit -
Back-outs clipped out of areas
Works out how much of an area a back-out covers, so that part can be taken off the area's quantity.
- TakeoffCraft
- 4 calculations in 2 files
64-bit -
Baked physics key times
The times of the keys written when rigid body physics is baked to the timeline.
- ModelCraft
- 1 calculation
64-bit -
Block model, ultimate pit and mine schedule
Estimates block grades from samples, values each block, finds the most valuable pit within a slope, and reports tonnes, grades, strip ratio and a discounted schedule.
- CivilCraft
- 10 calculations
64-bit -
Board placement and routing
Where parts are placed and where tracks and vias run on a board, with the wire length reported.
Every app 64-bit, stated limit- 8 calculations in 2 files
64-bit Open item -
Buckling load factors and thermal stress setup
Finds the lowest load factors at which a part buckles and their shapes, and sets up thermal loads for a stress study on the voxel model.
- PartCraft
- 7 calculations
64-bit -
Building mass areas, levels and base earthwork
Works out a building mass's footprint area, gross floor area, height, floor levels, the ground under it and the cut and fill to set it on the slope.
- CivilCraft
- 9 calculations
64-bit -
Building masses as IFC
Writes building masses as an IFC4 file: footprints, storey levels, heights and areas.
- CivilCraft
- 6 calculations
64-bit -
Cabinet job cost estimate
Prices a cabinet job from its sheets, edge banding, frame stock, hardware, countertops, labor and machine time, with markup and tax.
- CadCraft
- BimCraft
- ModelCraft
- PartCraft
- 10 calculations
64-bit Open item -
Cabinet job edits that change sizes
Works out the sizes an edit puts into a cabinet job: the job in the other unit, a filler for a leftover, a gap at a door or window, and the notch of a new L or U room.
- CadCraft
- BimCraft
- ModelCraft
- PartCraft
- 4 calculations
64-bit Open item -
Cabinet material sizes, grooves and drill files
Holds the thicknesses of the sheet materials and edge bands, derives the groove and sheet size from the picks, and writes the drill and G-code files.
- CadCraft
- BimCraft
- ModelCraft
- PartCraft
- 5 calculations in 2 files
64-bit -
Cabinet run layout and countertops
Places every cabinet, filler and end panel along its wall or island, works out how runs meet at corners, and sizes the countertops.
- CadCraft
- BimCraft
- ModelCraft
- PartCraft
- 19 calculations in 2 files
64-bit Open item -
Cabinet shop drawings as drawing objects
Turns the cabinet plan, elevations, sections, schedule, cut list and nested sheets into lines, polylines, texts, hatches and dimensions of the open drawing (CabinetCraft add-on).
- CadCraft
- BimCraft
- ModelCraft
- PartCraft
- 6 calculations
64-bit Open item -
CabinetCraft in a drawing: units, room outline and solids
Reads a room from a closed polyline of the drawing in millimeters, converts cabinet shop drawings and 3D solids to the drawing's unit, and decides where the sheets are drawn (CabinetCraft add-on in CadCraft).
- CadCraft
- 7 calculations
64-bit Open item -
CabinetCraft parts, fronts and face frames
Works out the cut-list parts of a cabinet job: face-frame stiles and rails, overlay doors and drawer fronts, drawer boxes, blind panels, fillers and end panels.
- CadCraft
- BimCraft
- ModelCraft
- PartCraft
- 11 calculations
64-bit Open item -
Cabinets on angled and curved walls
The geometry of cabinets on walls that are not at right angles or are curved: arc walls from radius, sweep or three points, cabinets stepped round an arc, and the corner cabinet at any angle (CabinetCraft add-on).
- CadCraft
- BimCraft
- ModelCraft
- PartCraft
- 16 calculations
64-bit Open item -
Cable routes in trays and conduits on the installation plan
Turns the routes drawn on the plan and the circuits into cables with a route, and into the fill rows of each tray and conduit.
- CadCraft
- 3 calculations
64-bit -
CalculiX deck export and result import
Writes a nonlinear study as a text input deck for the separate CalculiX program and reads its text result file back.
- PartCraft
- 6 calculations
64-bit Open item -
Camera exposure and white balance
The exposure value shown in the render dialog, the exposure in stops, and the color gains for a white-balance temperature.
- BimCraft
- ModelCraft
- 4 calculations
64-bit -
Capital and operating cost
Estimates the purchased and installed cost of process equipment and the yearly cost of its energy.
- CadCraft
- BimCraft
- 5 calculations
64-bit -
Circles tangent to two or three objects
Finds the circle of a given radius tangent to two picked lines or circles, and the circle tangent to three.
- CadCraft
- 8 calculations
64-bit Open item -
Circuit board outline, holes and part boxes
Reads a KiCad board file into a part: the board outline, its drilled holes and one box per component.
- PartCraft
- 5 calculations
64-bit -
Circuit solver
Operating point, DC sweep, AC response and transient of a circuit of resistors, capacitors, inductors, sources, diodes, transistors and switches.
Every app 64-bit, stated limit- 18 calculations in 2 files
64-bit Open item -
Clash check between parts
Finds steel parts and footings that run into each other and reports how deep and where.
- DetailCraft
- 9 calculations
64-bit -
Clear-sky solar irradiance
Estimates the beam and diffuse solar irradiance on a clear day from the day of the year, the sun's height, the site altitude and a climate type.
- CivilCraft
- 1 calculation
64-bit -
Closed-loop joint solver
Finds joint values that make every closed chain of joints in an assembly meet, and reports how many values remain free.
- PartCraft
- 6 calculations
64-bit -
Concrete member and slab checks on a solved frame
Checks every concrete beam and column of a solved frame for every strength combination, magnifies the moments of slender columns, and sizes a slab's reinforcement from the plate moments.
- CadCraft
- BimCraft
- DetailCraft
- 11 calculations in 3 files
64-bit -
Concrete member strength to ACI 318-19
The design strengths of a rectangular reinforced concrete section in bending, shear and combined axial force and bending.
- CadCraft
- BimCraft
- DetailCraft
- 9 calculations
64-bit Open item -
Concrete section by strain compatibility
The axial force and moment a rectangular reinforced concrete section carries for a given neutral axis depth, and the depth that balances a given axial force.
- CadCraft
- BimCraft
- DetailCraft
- 5 calculations
64-bit -
Conduit and tray fill, cable schedule
Works out how full a conduit or cable tray is, picks the smallest conduit that holds a set of cables, routes cables through the carriers and lists their lengths.
- CadCraft
- BimCraft
- 8 calculations
64-bit Open item -
Connection autopilot starting sizes
Proposes a connection for every joint that has none: bolt size and count, plate sizes and rod spacing, from the shapes and an optional end shear.
- DetailCraft
- 6 calculations
64-bit 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.