topic Re: Difference of geometryOrOriginOne and geometryOrOriginOneTwo in Fusion API and Scripts Forum

Difference of geometryOrOriginOne and geometryOrOriginOneTwo

yamamoto.mas — Sun, 01 Nov 2020 06:54:58 GMT

What is the difference between geometryOrOriginOne and geometryOrOriginOneTwo of JointInput Object.

I found their origin coordinates are sometimes identical and sometimes different.

I'd like to know which has true joint's coordinates.

This might be a basic question, but I could not find any explanation about it.

Re: Difference of geometryOrOriginOne and geometryOrOriginOneTwo

yamamoto.mas — Tue, 03 Nov 2020 02:24:09 GMT

I have further investigated the difference through experiments.

I compared two models:

"joint_test1 v2.f3d": Four 5cm blocks are stacked with joints located at other than component origins.

"joint_test2 v2.f3d": Four 5cm blocks are stacked with joints located at each component origin.

In this first case OriginOne vector shows joint position in world coordinate, while OriginTwo vector shows local coordinate.

In this second case, OriginOne vector is just garbage (zero vector), while OriginTwo vector is correctly showing local coordinates.

So, second case is very inconvenient to know world coordinate of the joint.

Is there anyway to know the joint's world coordinate constantly, irrespective of component's condition ?

Re: Difference of geometryOrOriginOne and geometryOrOriginOneTwo

yamamoto.mas — Tue, 03 Nov 2020 04:53:03 GMT

The first picture above is wrong. It should be swapped to:

Re: Difference of geometryOrOriginOne and geometryOrOriginOneTwo

yamamoto.mas — Thu, 05 Nov 2020 09:52:26 GMT

Combining the fact that

joint.geometryOrOriginTwo.origin.asArray() constantly return relative coordinate of the joint
joint.occurrenceTwo.transform.translation.asArray() returns the link origin

I come to the conclusion like this. It seems working for both cases.

import adsk.core, adsk.fusion, traceback try: app = adsk.core.Application.get() ui = app.userInterface product = app.activeProduct design = adsk.fusion.Design.cast(product) rootComp = design.rootComponent for joint in rootComp.joints: xyz_from_two_to_joint = joint.geometryOrOriginTwo.origin.asArray() xyz_of_two = joint.occurrenceTwo.transform.translation.asArray() xyz_of_joint = [a+b for a, b in zip(xyz_from_two_to_joint, xyz_of_two)] print("Joint position ", xyz_of_joint) except: print('Failed:\n{}'.format(traceback.format_exc()))

Re: Difference of geometryOrOriginOne and geometryOrOriginOneTwo

yamamoto.mas — Sat, 07 Nov 2020 04:27:56 GMT

I have generalized the algorithm so that it can cope with the case like this.

import adsk.core, adsk.fusion, traceback # Coordinate transformation by matrix # M: 4x4 transformation matrix # a: 3D vector def trans(M, a): ex = [M[0],M[4],M[8]] ey = [M[1],M[5],M[9]] ez = [M[2],M[6],M[10]] oo = [M[3],M[7],M[11]] b = [0, 0, 0] for i in range(3): b[i] = a[0]*ex[i]+a[1]*ey[i]+a[2]*ez[i]+oo[i] return(b) # Returns True if two arrays are element-wise equal within a tolerance def allclose(v1, v2, tol=1e-6): return( max([abs(a-b) for a,b in zip(v1, v2)]) < tol ) try: app = adsk.core.Application.get() ui = app.userInterface product = app.activeProduct design = adsk.fusion.Design.cast(product) rootComp = design.rootComponent for joint in rootComp.joints: # Basic information xyz_from_one_to_joint = joint.geometryOrOriginOne.origin.asArray() # Relative Joint pos xyz_from_two_to_joint = joint.geometryOrOriginTwo.origin.asArray() # Relative Joint pos xyz_of_one = joint.occurrenceOne.transform.translation.asArray() # Link origin xyz_of_two = joint.occurrenceTwo.transform.translation.asArray() # Link origin M_two = joint.occurrenceTwo.transform.asArray() # Matrix as a 16 element array. # Compose joint position case1 = allclose(xyz_from_two_to_joint, xyz_from_one_to_joint) case2 = allclose(xyz_from_two_to_joint, xyz_of_one) if case1 or case2: xyz_of_joint = xyz_from_two_to_joint else: xyz_of_joint = trans(M_two, xyz_from_two_to_joint) # Show result print('-----', joint.name, '-----') print('J1', [round(x,3) for x in xyz_from_one_to_joint]) print('J2', [round(x,3) for x in xyz_from_two_to_joint]) print('L1', [round(x,3) for x in xyz_of_one]) print('L2', [round(x,3) for x in xyz_of_two]) print(case1, case2) print("Joint position ", [round(x, 3) for x in xyz_of_joint]) except: print('Failed:\n{}'.format(traceback.format_exc()))

I'm still skeptical about the result:

* Can this algorithm cope with all possible cases ?

* Do AUTODESK engineers do such complicated computation just to get joint coordinates ?