topic Re: Radius of tangent circle cannot be set properly in Fusion API and Scripts Forum

Radius of tangent circle cannot be set properly

marcinszydlowski.1984 — Tue, 14 Apr 2020 19:05:55 GMT

Hello,

I have a problem with proper setting radius of circle when:

circle is tangent to arcs
Z coordinate of those arcs and circle is different than 0

I checked it for lines and then it works. I use newest version of Fusion for Windows, monthly subscription.

Code:

import adsk.core, adsk.fusion def run(context): app = adsk.core.Application.get() product = app.activeProduct design = adsk.fusion.Design.cast(product) rootComponent = design.rootComponent design.designType = adsk.fusion.DesignTypes.DirectDesignType sketch = rootComponent.sketches.add(rootComponent.xYConstructionPlane) # Lines - z=0 OK, radius of circle is 1 z = 0 p11 = adsk.core.Point3D.create(2, 1, z) p12 = adsk.core.Point3D.create(5, 1.5, z) p21 = adsk.core.Point3D.create(1, 1, z) p22 = adsk.core.Point3D.create(2.6, 6, z) line1 = sketch.sketchCurves.sketchLines.addByTwoPoints(p11, p12) line2 = sketch.sketchCurves.sketchLines.addByTwoPoints(p21, p22) circle1 = sketch.sketchCurves.sketchCircles.addByCenterRadius(adsk.core.Point3D.create(4, 4, z), 1) # Make circle tangent to lines line1.isFixed = True line2.isFixed = True sketch.geometricConstraints.addTangent(circle1, line1) sketch.geometricConstraints.addTangent(circle1, line2) # Lines - z=5 OK, radius of circle is 1 z = 5 p11 = adsk.core.Point3D.create(2, 1, z) p12 = adsk.core.Point3D.create(5, 1.5, z) p21 = adsk.core.Point3D.create(1, 1, z) p22 = adsk.core.Point3D.create(2.6, 6, z) line1 = sketch.sketchCurves.sketchLines.addByTwoPoints(p11, p12) line2 = sketch.sketchCurves.sketchLines.addByTwoPoints(p21, p22) circle1 = sketch.sketchCurves.sketchCircles.addByCenterRadius(adsk.core.Point3D.create(4, 4, z), 1) # Make circle tangent to lines line1.isFixed = True line2.isFixed = True sketch.geometricConstraints.addTangent(circle1, line1) sketch.geometricConstraints.addTangent(circle1, line2) # Arcs - z=0 OK, radius of circle is 1 z = 0 p1s = adsk.core.Point3D.create(12, 1, z) p1e = adsk.core.Point3D.create(15, 1.5, z) p1m = adsk.core.Point3D.create(13.5, 1.4, z) p2s = adsk.core.Point3D.create(11, 1, z) p2e = adsk.core.Point3D.create(12.6, 6, z) p2m = adsk.core.Point3D.create(11.5, 3.8, z) p1sSketch = sketch.sketchPoints.add(p1s) p1eSketch = sketch.sketchPoints.add(p1e) arc1 = sketch.sketchCurves.sketchArcs.addByThreePoints(p1sSketch, p1m, p1eSketch) p2sSketch = sketch.sketchPoints.add(p2s) p2eSketch = sketch.sketchPoints.add(p2e) arc2 = sketch.sketchCurves.sketchArcs.addByThreePoints(p2sSketch, p2m, p2eSketch) circle2 = sketch.sketchCurves.sketchCircles.addByCenterRadius(adsk.core.Point3D.create(14, 4, z), 1) arc1.isFixed = True arc2.isFixed = True sketch.geometricConstraints.addTangent(circle2, arc1) sketch.geometricConstraints.addTangent(circle2, arc2) circle2.radius = 1 # Arcs - z=5 WRONG, radius of circle is not 1 z = 5 p1s = adsk.core.Point3D.create(12, 1, z) p1e = adsk.core.Point3D.create(15, 1.5, z) p1m = adsk.core.Point3D.create(13.5, 1.4, z) p2s = adsk.core.Point3D.create(11, 1, z) p2e = adsk.core.Point3D.create(12.6, 6, z) p2m = adsk.core.Point3D.create(11.5, 3.8, z) p1sSketch = sketch.sketchPoints.add(p1s) p1eSketch = sketch.sketchPoints.add(p1e) arc1 = sketch.sketchCurves.sketchArcs.addByThreePoints(p1sSketch, p1m, p1eSketch) p2sSketch = sketch.sketchPoints.add(p2s) p2eSketch = sketch.sketchPoints.add(p2e) arc2 = sketch.sketchCurves.sketchArcs.addByThreePoints(p2sSketch, p2m, p2eSketch) circle2 = sketch.sketchCurves.sketchCircles.addByCenterRadius(adsk.core.Point3D.create(14, 4, z), 1) arc1.isFixed = True arc2.isFixed = True sketch.geometricConstraints.addTangent(circle2, arc1) sketch.geometricConstraints.addTangent(circle2, arc2) circle2.radius = 1

Re: Radius of tangent circle cannot be set properly

BrianEkins — Wed, 15 Apr 2020 01:47:34 GMT

I tried running your code and it runs without any errors but I don't know if the result is what you expect. What is the specific problem? One thing I would be cautious of is drawing things of the X-Y sketch plane and expecting constraints to behave like normal. In the UI you're limited to what you can do with curves that aren't on the X-Y sketch plane. For example, I can't add a dimension constraint to the circles. You would be better off having to sketches, one for each Z height.

Re: Radius of tangent circle cannot be set properly

marcinszydlowski.1984 — Wed, 15 Apr 2020 05:49:39 GMT

Hi Brian,

the problem is that circle2.radius = 1 in the fourth example:

... # Arcs - z=5 WRONG, radius of circle is not 1 z = 5 p1s = adsk.core.Point3D.create(12, 1, z) p1e = adsk.core.Point3D.create(15, 1.5, z) p1m = adsk.core.Point3D.create(13.5, 1.4, z) p2s = adsk.core.Point3D.create(11, 1, z) p2e = adsk.core.Point3D.create(12.6, 6, z) p2m = adsk.core.Point3D.create(11.5, 3.8, z) p1sSketch = sketch.sketchPoints.add(p1s) p1eSketch = sketch.sketchPoints.add(p1e) arc1 = sketch.sketchCurves.sketchArcs.addByThreePoints(p1sSketch, p1m, p1eSketch) p2sSketch = sketch.sketchPoints.add(p2s) p2eSketch = sketch.sketchPoints.add(p2e) arc2 = sketch.sketchCurves.sketchArcs.addByThreePoints(p2sSketch, p2m, p2eSketch) circle2 = sketch.sketchCurves.sketchCircles.addByCenterRadius(adsk.core.Point3D.create(14, 4, z), 1) arc1.isFixed = True arc2.isFixed = True sketch.geometricConstraints.addTangent(circle2, arc1) sketch.geometricConstraints.addTangent(circle2, arc2) circle2.radius = 1

doesn't work for arcs on z = 5 but similar code works for lines (second example):

... # Lines - z=5 OK, radius of circle is 1 ...

I changed radius of circle in the second example after applying constraints and it works.

But it doesn't when I use arcs:

All examples visibleView from top (along Z axis)

My target is to set all radiuses equals in one sketch. I can use many sketches but without direct design it'll expand timeline significantly and slow down Fusion. I cannot use sweep in this case. I also tried parametric design with adding radial dimension (as driving) to the circle but it didn't help.

I want to know if I do something wrong or it is specific behaviour for constraints with arcs and I have to do workaround for it.

Re: Radius of tangent circle cannot be set properly

marcinszydlowski.1984 — Wed, 15 Apr 2020 07:10:27 GMT

If it's not a bug, please close this. I've handled this using cosines theorem which is enough for my case.

Re: Radius of tangent circle cannot be set properly

marcinszydlowski.1984 — Tue, 21 Apr 2020 05:55:03 GMT

Ok. As a quick workaround for this particular case I used law of cosines. I always need one case (two intersection points of circles and third circle inside the second one) so formula will be always the same. Another assumption is that circles/arcs are intersect together in two points.

For those of you who have similar problem with proper radius between three tangent circles/arcs on coordinate Z different than 0 here's the idea and solution.

We need to find the center of red circle for given radius

Symbols:

O1 - known center of circle/arc 1
O2 - known center of circle/arc 2
r1 - known radius of circle/arc 1
r2 - known radius of circle/arc 2
r3 - desired radius of circle/arc 3
d - known distance between centers of circles/arcs 1 and 2
r1 + r3 - known distance between centers of circles/arcs 1 and 3
r2 - r3 - known distance between centers of circles/arcs 2 and 3
alpha - angle between vectors d and r1r3
betha - angle between vector [1, 0, 0] and r1r3
O3 - unknown center of circle/arc 3

The idea is to find center of circle 3 based on distance r1 + r3 and angle alpha + betha.

Cosine theorem for triangle O1 O2 O3 is:

Cosine formula for triangle O1 O2 O3

By transforming this we can obtain alpha angle:

Alpha angle

This is all we need. All script showing an example is listed below.

import math import adsk.core, adsk.fusion def run(context): app = adsk.core.Application.get() product = app.activeProduct design = adsk.fusion.Design.cast(product) rootComp = design.rootComponent # Assumption that circle 3 is inside circle 2 and near the top intersection point of circles 1 and 2 z = 3 # Circle 1 radius1 = 3.1 center1 = adsk.core.Point3D.create(-1, 0.5, z) # Circle 2 radius2 = 2.03 center2 = adsk.core.Point3D.create(3.5, 1.2, z) # Draw circle 1 and 2 sketch = rootComp.sketches.add(rootComp.xYConstructionPlane) sketch.sketchCurves.sketchCircles.addByCenterRadius(center1, radius1) sketch.sketchCurves.sketchCircles.addByCenterRadius(center2, radius2) # Show wait adsk.core.Application.get().userInterface.messageBox("Click to continue...", "Waiting") # Circle 3 radius3 = 0.9 # Calculations d = center1.distanceTo(center2) r1r3 = radius1 + radius3 r2r3 = radius2 - radius3 alpha = math.acos((r2r3**2 - r1r3**2 - d**2) / (-2 * r1r3 * d)) betha = center1.vectorTo(center2).angleTo(adsk.core.Vector3D.create(1, 0, 0)) center3x = center1.x + r1r3 * math.cos(alpha + betha) center3y = center1.y + r1r3 * math.sin(alpha + betha) center3 = adsk.core.Point3D.create(center3x, center3y, z) sketch.sketchCurves.sketchCircles.addByCenterRadius(center3, radius3)

Formulas for other cases (outside circles, other intersection point, different direction) will be slightly different but idea is the same. The only differences will be with signs +/-. You have to remember that for non-intersecting circles/arcs it'll raise cosine domain error so you need to change approach.

Re: Radius of tangent circle cannot be set properly

marcinszydlowski.1984 — Fri, 15 May 2020 04:53:08 GMT

Thank you @BrianEkins for the tip. It seems that keeping profiles or other important features per sketch is the best solution so far.