Script - Discrepancy in the precision length, height and width

YouElz · ‎03-31-2024

Hello everyone,

I've recently begun experimenting with scripting for Fusion 360, focusing on simple tasks like extracting component or body dimensions such as Length, Height, and Width. I think I've successfully retrieved these dimensions, but I've noticed a discrepancy in the precision of the values displayed by the script (see attached image) compared to when they are inspected directly within the Fusion 360 design.

Here are the body dimensions (in Design):

Length: 200.0 mm
Width: 150.00 mm
Height: 300.00 mm

@BrianEkins

import traceback
import adsk.fusion
import adsk.core

def run(context):
    ui = adsk.core.UserInterface.cast(None)
    try:
        app: adsk.fusion.Application = adsk.core.Application.get()
        ui = app.userInterface
        des: adsk.fusion.Design = app.activeProduct
        comp: adsk.fusion.Component = des.activeComponent

        mMgr:adsk.core.MeasureManager = app.measureManager

        OBBox: adsk.core.OrientedBoundingBox3D = mMgr.getOrientedBoundingBox(
                                                        comp.bRepBodies[0],
                                                        comp.yConstructionAxis.geometry.direction,
                                                        comp.xConstructionAxis.geometry.direction)

        unitsMgr: adsk.core.UnitsManager = des.unitsManager
        defLenUnit = unitsMgr.defaultLengthUnits
        ratio = unitsMgr.convert(1, unitsMgr.internalUnits, defLenUnit)

        msg = [
            f'length : {OBBox.length * ratio} {defLenUnit}',
            f'width : {OBBox.width * ratio} {defLenUnit}',
            f'height : {OBBox.height * ratio} {defLenUnit}',
        ]

        ui.messageBox('\n'.join(msg))

    except:
        if ui:
            ui.messageBox('Failed:\n{}'.format(traceback.format_exc()))

kandennti · ‎03-31-2024

Hi @YouElz -San.

The possibility of incorrect representation of real numbers is possible in any programming language.

・・・
        msg = [
            f'length : {round(OBBox.length * ratio, 3)} {defLenUnit}',
            f'width : {round(OBBox.width * ratio, 3)} {defLenUnit}',
            f'height : {round(OBBox.height * ratio, 3)} {defLenUnit}',
        ]
・・・

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YouElz · ‎04-01-2024

Hi @kandennti

I am wondering if it has to do with the OrientedBoundingBox:

oBBox: adsk.core.OrientedBoundingBox3D = mMgr.getOrientedBoundingBox(
                                                        comp.bRepBodies[0],
                                                        comp.yConstructionAxis.geometry.direction,
                                                        comp.xConstructionAxis.geometry.direction)

looking at the API I found formatValue method of UnitsManger

        Given a floating point number this method evaulates it as a value of a specific unit type
        and returns an appropriate string. By default, the current unit settings defined
        in the user preferences is used, but you can set the method arguments to override
        the defaults to specify the formatting you want. The input value always uses internal
        units, which are centimeters for length, radians for angles, and mass is in kilograms.
        
        This method is useful whenever you have a value you've gotten from Fusion or computed on your
        own and need to display it to the user as a string. This method does the conversion and also
        takes into account the units and the formatting the user has specified in their preferences.

I used it this way and it seems the value is being displayed correctly, however, I am not sure if this is the right way to do it.

    unitsMgr: adsk.core.UnitsManager = design.unitsManager
    length = unitsMgr.formatValue(OBBox.length)
    width  = unitsMgr.formatValue(OBBox.width)
    height  = unitsMgr.formatValue(OBBox.height)

kandennti · ‎04-02-2024

@YouElz -San.

I think that is most correct.

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