Resources
Numerical accuracy
The calculations in our apps: the policy each one is under, the precision it runs at, and the code itself.
This device: processor, memory, graphics The standard Precision is not robustness
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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Forces and deflection along a member
The axial force, shears, torque, bending moments and deflected shape along each member, and the largest values the report and the design checks read.
- CadCraft
- BimCraft
- DetailCraft
- 4 calculations
64-bit Open item -
Foundation parts and quantities
Sizes footings from a default table, builds the slab, stem wall and footing shapes under the building outline, steps them to the ground, and writes their lengths, widths and volumes.
- BimCraft
- 8 calculations
64-bit Open item -
Frame analysis with slabs, walls and rigid floors
Solves a frame that has plates and rigid floor diaphragms, and works out plate results at nodes and the drift of each story.
- CadCraft
- BimCraft
- DetailCraft
- 12 calculations
64-bit Open item -
Frame analysis: loads, releases, end forces and reactions
Turns loads into nodal forces, takes released ends out of each member, and works out member end forces, support reactions and the load and reaction totals of a solved frame.
- CadCraft
- BimCraft
- DetailCraft
- 13 calculations
64-bit -
Frame model from a building model
Turns the model's beams, columns, braces and concrete slabs and walls into the lines, sections, joints, supports and loads the frame analysis solves.
- BimCraft
- 17 calculations
64-bit Open item -
Framing panels and cut lists
Lays out the studs, plates, headers, joists and rafters of a framing panel, lists the pieces to cut, and places them in the model as members.
- BimCraft
- DetailCraft
- 12 calculations
64-bit Open item -
Furniture layout of a room
Places a room's furniture by rule: against the walls or in the middle, clear of doors, windows and each other.
- BimCraft
- ModelCraft
- 9 calculations
64-bit -
G-code dry run and hole check
Reads a generated G-code file and reports its extent, cutting and rapid lengths, depths and cutting time, and checks that every drilled hole lies on its panel.
- CadCraft
- BimCraft
- ModelCraft
- PartCraft
- 10 calculations
64-bit Open item -
Gaussian plume concentration and contours
Works out the concentration downwind of a continuous release, how far a concentration level reaches, and the outline of that level on a site plan.
- CadCraft
- BimCraft
- 7 calculations
64-bit Open item -
GDSII layout: reals, flattening, areas and checks
Reading and writing chip layout streams, flattening cell hierarchies, layer areas and the basic width, spacing and area checks.
Every app 64-bit, stated limit- 12 calculations
64-bit 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 -
Georeference written to the IFC file
Writes a model's place on the map into the file: the map conversion numbers, the coordinate reference system and its length unit.
- BimCraft
- 5 calculations
64-bit -
Gerber and drill file numbers
The coordinates and sizes written to Gerber layers, drill files and the job file, and read back from them.
Every app 64-bit, stated limit- 7 calculations
64-bit Open item -
Grid lines
Lays out grid lines by spacing and angle, finds where they cross for snapping, and decides which lines an elevation sees end on.
- BimCraft
- 6 calculations
64-bit -
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 -
Ground surface triangulation and contours
Builds the triangulated ground surface from points, breaklines and a boundary, and works out its contours, elevation bands and outline.
- BimCraft
- CivilCraft
- 17 calculations
64-bit -
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 -
Hazardous area extents and zone geometry
Works out how far a flammable zone extends from a release source, the zone shapes in plan, section and 3D, and the files that carry them to a site plan.
- CadCraft
- BimCraft
- 10 calculations in 2 files
64-bit 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 -
Heat exchanger rating
Works out the duty, outlet temperatures, film coefficients, required area, pressure drops and tube count of a shell-and-tube, plate or air-cooled exchanger, and screens tubes for vibration.
- CadCraft
- BimCraft
- 18 calculations in 2 files
64-bit Open item -
Heat-exchanger network design
Proposes the matches, heaters and coolers of a heat-exchanger network from stream data by the pinch design method, with the duty and end temperatures of each.
- CadCraft
- BimCraft
- 5 calculations
64-bit -
Heating and cooling loads per room
Works out what bounds each room, the U-value of each bounding element, and from them the design heating load, a degree-day year and a cooling peak.
- BimCraft
- 11 calculations
64-bit -
I/O channel counts with spare allowance
Counts the control system channels of each type on a P&ID and adds the spare allowance.
- CadCraft
- BimCraft
- 1 calculation
64-bit Open item -
IFC 4.3 infrastructure quantities and files
Reads the quantities, stations and alignment lengths of roads, railways, bridges and other infrastructure from an IFC file, totals them per class, and writes a new IFC 4.3 file.
- BimCraft
- TakeoffCraft
- CivilCraft
- DetailCraft
- 9 calculations
64-bit Open item -
IFC alignment curves and stations
Reads the alignment curves of an IFC 4.3 file as sampled 3D polylines, finds the point at a station, places elements along them and builds solids swept between cross sections.
- BimCraft
- TakeoffCraft
- CivilCraft
- DetailCraft
- 7 calculations
64-bit Open item -
IFC curves and profiles as point lists
Turns the curves and cross-section profiles of an IFC file into polylines: arcs, circles, ellipses, trimmed curves, B-splines, offsets, and the standard steel shapes with their fillets.
- BimCraft
- TakeoffCraft
- CivilCraft
- DetailCraft
- 10 calculations in 2 files
64-bit Open item -
IFC faces on curved surfaces
Tessellates faces that lie on cylinders, cones, spheres, tori, swept surfaces and B-spline surfaces into triangles.
- BimCraft
- TakeoffCraft
- CivilCraft
- DetailCraft
- 11 calculations
64-bit -
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 length unit and placement matrices
Finds how many millimeters one length unit of an IFC file is, and multiplies, inverts and applies the 4 × 4 placement matrices used when reading and placing elements.
- BimCraft
- 6 calculations
64-bit -
IFC measures in SI for USD
Converts IFC lengths, areas and volumes to meters, square meters and cubic meters when properties are written to USD.
- CadCraft
- BimCraft
- ModelCraft
- TakeoffCraft
- CivilCraft
- DetailCraft
- PartCraft
- 1 calculation
64-bit -
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 -
IFC swept solids, primitives and faceted shapes
Builds the meshes of extruded, revolved and swept solids, swept disks such as rebar and pipes, the basic primitives, and faceted boundary shapes.
- BimCraft
- TakeoffCraft
- CivilCraft
- DetailCraft
- 10 calculations in 2 files
64-bit -
IFC units and placements
Reads the length and angle units of an IFC file and turns its placements, transformation operators, grid placements and map conversion into 4 × 4 matrices.
- BimCraft
- TakeoffCraft
- CivilCraft
- DetailCraft
- 13 calculations in 2 files
64-bit -
Imported carbon factors, prices and climate data
Reads a person's own carbon-factor file, cost book or climate answer into the tables the carbon, cost and solar panes calculate from.
- BimCraft
- 5 calculations
64-bit Open item -
Interior elevations and their dimensions
Frames each wall of a room as an interior elevation, writes its width, height and level dimensions, and turns placed items.
- BimCraft
- 7 calculations in 2 files
64-bit -
Inverse kinematics and joint trajectories
Joint angles that put a robot link at a target, and timed joint moves with their speeds, accelerations and peak torques.
Every app 64-bit, stated limit- 9 calculations in 2 files
64-bit -
Issue viewpoints in BCF files
Converts cameras and section planes between the viewer and the model's own coordinates, and writes and reads them in BCF issue files.
- BimCraft
- ModelCraft
- 8 calculations
64-bit Open item -
Joist depth from a span table the person loads
Picks the smallest joist depth whose listed clear span reaches the span asked for, from a table the person loads.
- BimCraft
- 6 calculations
64-bit -
Lab results to stream composition
Turns lab results in mass, mole, ppm or mg/L terms into a proposed stream composition in mole fractions, and writes calculated compositions back in the lab's terms.
- CadCraft
- BimCraft
- 2 calculations
64-bit -
LAS and LAZ point coordinates
Reads a LiDAR file's header and turns each stored point into x, y, z in the file's coordinates.
- CadCraft
- BimCraft
- CivilCraft
- 4 calculations
64-bit -
Layer of protection and SIL arithmetic
Works out the mitigated frequency of a hazard scenario, the risk reduction still needed, and the average probability of failure on demand of a safety function with its SIL band.
- CadCraft
- BimCraft
- 7 calculations
64-bit Open item -
Layout point files and as-built comparison
Writes points for a total station as a text file, reads such a file back, and compares as-built points with the design.
- CadCraft
- BimCraft
- 6 calculations
64-bit -
Length tags and tag schedules
Keeps a length tag on an element as an IFC property and lists tag values in schedules, in millimeters.
- BimCraft
- 3 calculations
64-bit -
Lengths and units for Library items
Reads lengths written as text (30", 2'-6 1/2", 762 mm) into millimeters and writes sizes back as short labels.
- CadCraft
- BimCraft
- 5 calculations
64-bit Open item -
Lengths, areas and volumes as text
Turns a length in millimeters, an area or a volume into text in the display unit a person picked.
- BimCraft
- 9 calculations
64-bit -
Library 3D preview
The 3D view of an item on its Library page and on the configure page.
Every app Display only- 3 calculations in 2 files
32-bit, display only -
Library configurator sizes
The size and connection positions shown for the chosen variant on a Library item's configure page.
Every app 64-bit, direct- 2 calculations
64-bit -
Library item geometry from blocks, meshes and tables
Builds a Library item's plan and 3D body in millimeters from a drawing block, a mesh file (glTF, OBJ, STL) or a table of sizes.
- CadCraft
- BimCraft
- 18 calculations
64-bit 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
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.