Adding more points (in a loop) makes my sketch unconstrained

[timJ4DLL]

I am trying to place points in 3D space according to parametric mathematical formulas (and join them with a spline, but that's not relevant here).

If I have 5 or fewer iterations in my loop (5 construction points + 5 spline points for a total of 10 points), my sketch is fully constrained.

If I have 6 or more iterations (12 or more points), my sketch is not fully constrained.

Here it is with 10 iterations. As you can see, only the first 5 point pairs are constrained.

As I am applying all the same constraints to all points - it's a loop - this makes no sense to me. Can anyone explain what's going on?

import adsk
from adsk.core import (Application, ObjectCollection, Point3D, ValueInput)
from adsk.fusion import (Design, DimensionOrientations)
import math, traceback

handlers = []

def run(context):
    ui = None
    try:
        app = Application.get()
        ui  = app.userInterface

        drawSplines = ui.commandDefinitions.addButtonDefinition(
            "DrawTrigSpline",
            "Draw Trig Spline",
            "Draw Trig Spline"
        )

        drawSplinesCreated = DrawSplinesCreatedEventHandler()
        drawSplines.commandCreated.add(drawSplinesCreated)
        handlers.append(drawSplinesCreated)

        drawSplines.execute()

        adsk.autoTerminate(False)

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

def stop(context):
    try:
        app = adsk.core.Application.get()
        ui  = app.userInterface
        
        # Delete the command definition.
        cmdDef = ui.commandDefinitions.itemById('DrawTrigSpline')
        if cmdDef:
            cmdDef.deleteMe()            
    except:
        if ui:
            ui.messageBox('Failed:\n{}'.format(traceback.format_exc()))


class DrawSplinesCreatedEventHandler(adsk.core.CommandCreatedEventHandler):
    def __init__(self):
        super().__init__()

    def notify(self, args):
        args = adsk.core.CommandCreatedEventArgs.cast(args)

        onExecute = DrawSplinesExecuteEventHandler()
        args.command.execute.add(onExecute)
        handlers.append(onExecute)


class DrawSplinesExecuteEventHandler(adsk.core.CommandEventHandler):
    def __init__(self):
        super().__init__()

    def notify(self, args):
        ui = None

        try:
            app = Application.get()
            ui  = app.userInterface
            
            # API uses cm for all lengths
            maj_d = 1
            min_d = 0.2

            # avoid dealing with zero or negative constraint distances
            xyoffset = maj_d * 2
            zoffset = min_d * 2

            # API uses rad for all angles, but these are in degrees and we convert them later
            minDeg = -90
            maxDeg = 90
            steps = 6

            design = Design.cast(app.activeProduct)
            parameters = design.userParameters
            parameters.add("maj_d", ValueInput.createByReal(maj_d), "mm", "major diameter")
            parameters.add("min_d", ValueInput.createByReal(min_d), "mm", "minor diameter")

            component = design.rootComponent
            refPlane = component.xYConstructionPlane

            sketch = component.sketches.add(refPlane)
            sketch.isComputeDeferred = True
            sketch.areProfilesShown = False

            origin = sketch.originPoint
            points = sketch.sketchPoints
            lines = sketch.sketchCurves.sketchLines
            constraints = sketch.geometricConstraints
            dimensions = sketch.sketchDimensions

            radials = []
            axials = []

            if steps > 1:
                stepDeg = (maxDeg - minDeg) / (steps - 1)
            else:
                stepDeg = 0

            for thetaDeg in (minDeg + i*stepDeg for i in range(steps)):
                thetaRad = thetaDeg * math.pi / 180
                r = maj_d
                x = xyoffset + r * math.sin(thetaRad)
                y = xyoffset + r * math.cos(thetaRad)
                z = zoffset + math.cos(4 * thetaRad) * (min_d/2)

                radial = points.add(Point3D.create(x,y,0))
                radials.append(radial)

                xDim = dimensions.addDistanceDimension(radial, origin,
                                                    DimensionOrientations.HorizontalDimensionOrientation,
                                                    Point3D.create(x/2,y,0))
                xDim.parameter.expression = f"{xyoffset} cm + sin({thetaDeg} deg) * maj_d"

                yDim = dimensions.addDistanceDimension(radial, origin,
                                                    DimensionOrientations.VerticalDimensionOrientation,
                                                    Point3D.create(x,y/2,0))
                yDim.parameter.expression = f"{xyoffset} cm + cos({thetaDeg} deg) * maj_d"


                axial = lines.addByTwoPoints(radial, Point3D.create(x, y, z))
                axial.isConstruction = True
                axials.append(axial)

                zDim = dimensions.addDistanceDimension(axial.endSketchPoint, radial,
                                                        DimensionOrientations.AlignedDimensionOrientation,
                                                        Point3D.create(x, y, z/2))
                zDim.parameter.expression = f"{zoffset} cm + {z / (min_d/2)} * (min_d/2)"
                

            sketch.isComputeDeferred = False

            for radial in radials:
                constraints.addCoincidentToSurface(radial, refPlane)

            for axial in axials:
                constraints.addPerpendicularToSurface(axial, refPlane)

            for constraint in constraints:
                if not constraint.isValid:
                    ui.messageBox(f'{constraint.classType} is not valid')

            adsk.terminate()

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

[CADacombs · Accepted solution]

The non-fully constrained sketch issue also exists for some "3D sketches" created via the UI: Solved: 3D Sketch won't fully constrain - Autodesk Community - Fusion

If you really want sketch.isFullyConstained to be True, one way is to set each radial.isFixed to True. (All isn't even necessary, only their count - 5.)