Loft issue "the selected rail does not touch all of the profiles" (Fusion API)

[Anonymous]

Hi, 

I am working on a parametric design using the fusion API, and I'm having an issue with the loft function. I have created guide rails using the fusion API sketchFittedSplines from a list of points Point3D.create(). The two profiles are rectangles generated from the first and last set of 3d points in the guide rails. The sketches appear to be correct, but the loft function fails. Lofting also fails when I attempt to do it manually in the Fusion 360 interface (see attached screenshot). Even though the profile is generated from points existing in the rails I get the error message "the selected rail does not touch all of the profiles". 

I hope someone can help me resolve this issue. 

My code for generating the rails: 

                sketch1 = rootComp.sketches.add(rootComp.xYConstructionPlane)

                sketch2 = rootComp.sketches.add(rootComp.xYConstructionPlane)

                sketch3 = rootComp.sketches.add(rootComp.xYConstructionPlane)

                sketch4 = rootComp.sketches.add(rootComp.xYConstructionPlane)

                sketch5 = rootComp.sketches.add(rootComp.xYConstructionPlane)

                sketch6 = rootComp.sketches.add(rootComp.xYConstructionPlane)

                g1 = adsk.core.ObjectCollection.create()

                g2 = adsk.core.ObjectCollection.create()

                g3 = adsk.core.ObjectCollection.create()

                g4 = adsk.core.ObjectCollection.create()

                for t in range(0,l_tot+1):

                    fac1(t) #specifics redacted

                    fac2(t) #specifics redacted

                    g1.add(adsk.core.Point3D.create(ofsx3_in*fac1+ofsx3_out*fac2, ofsy2_in*fac1+ofsy2_out*fac2, t))

                    g2.add(adsk.core.Point3D.create(ofsx3_in*fac1+ofsx3_out*fac2, ofsy3_in*fac1+ofsy3_out*fac2, t))

                    g3.add(adsk.core.Point3D.create(ofsx4_in*fac1+ofsx4_out*fac2, ofsy2_in*fac1+ofsy2_out*fac2, t))

                    g4.add(adsk.core.Point3D.create(ofsx4_in*fac1+ofsx4_out*fac2, ofsy3_in*fac1+ofsy3_out*fac2, t))

                rail1 = sketch1.sketchCurves.sketchFittedSplines.add(g1)

                rail2 = sketch2.sketchCurves.sketchFittedSplines.add(g2)

                rail3 = sketch3.sketchCurves.sketchFittedSplines.add(g3)

                rail4 = sketch4.sketchCurves.sketchFittedSplines.add(g4)

For generating the profiles and lofting: 

                # Draw the bottom rectangle

                lines1 = sketch5.sketchCurves.sketchLines

                recLines = lines1.addThreePointRectangle(g1[0], g2[0], g3[0])

                # Draw the top rectangle

                lines2 = sketch6.sketchCurves.sketchLines

                recLines = lines2.addThreePointRectangle(g1[-1], g2[-1], g3[-1])

                # Create loft feature input

                loftFeats = rootComp.features.loftFeatures

                loftInput = loftFeats.createInput(adsk.fusion.FeatureOperations.NewBodyFeatureOperation)

                # Loft Sections

                loftSectionsObj = loftInput.loftSections

                loftSectionsObj.add(sketch5.profiles.item(0))

                loftSectionsObj.add(sketch6.profiles.item(0))

                # Loft Guides

                loftInput.centerLineOrRails.addRail(rail1)

                loftInput.centerLineOrRails.addRail(rail2)

                loftInput.centerLineOrRails.addRail(rail3)

                loftInput.centerLineOrRails.addRail(rail4)

                loftInput.isSolid = True

                loftInput.operation = 1

                # Create loft feature

                loftFeats.add(loftInput)

[Anonymous]

Update: I measured the distance between the rails and the profiles and apparently there is a distance of 0.0000000000000044 mm at each corner. How can this be when I am using the exact same points as input?

[kandennti]

Hi @Anonymous .

I can not try it because there are no specific values and models.

It may be irrelevant, but there have been cases where increasing tolerance in the past has solved it.

https://forums.autodesk.com/t5/fusion-360-api-and-scripts/different-height-calculation-for-sweep-and-extrusion/m-p/9112909 
May be worth trying.

[Anonymous]

Thanks for the reply 🙂

I tried increasing the tolerance, but that didn't seem to do the trick. 

I am creating the lofts in a nested for loop and it works for every loft except the three closest to the center. I just can't understand why it doesn't work for those three specific cases. There is a total of 60*8 lofts, so it takes a while to run the script. If you want to try to run the full script you can send me a private message.