Hi Everyone,
Can we pull center of mass info in the api? I’d like to make a script to place a point based on the center of mass values. This will be super useful for anyone who needs to balance designs.
Thanks!
Mike
Can the Fusion API call center of mass information?
I don't understand why it is not working. I as well have been following the example but can't get it to work. I think it has to do with the difference between a 3Dpoint (the cog in this case) and a point object.
Anyway, I changed a couple of things and now the script will take you 80% there. You will need to manually click on the construction menu and select "point through three planes"
import adsk.core, adsk.fusion, adsk.cam, traceback
app = adsk.core.Application.get()
if app:
ui = app.userInterface
def run(context):
try:
activeDoc = adsk.core.Application.get().activeDocument
design = activeDoc.design
rootComp = design.rootComponent
physicalProperties = rootComp.getPhysicalProperties(adsk.fusion.CalculationAccuracy.HighCalculationAccuracy)
cog = physicalProperties.centerOfMass
planes=rootComp.constructionPlanes
planeX=planes.createInput()
planeX.setByOffset(rootComp.xYConstructionPlane,adsk.core.ValueInput.createByReal(cog.z))
planeY=planes.createInput()
planeY.setByOffset(rootComp.xZConstructionPlane,adsk.core.ValueInput.createByReal(cog.y))
planeZ=planes.createInput()
planeZ.setByOffset(rootComp.yZConstructionPlane,adsk.core.ValueInput.createByReal(cog.x))
planes.add(planeX)
planes.add(planeY)
planes.add(planeZ)
# Get construction points
constructionPoints = rootComp.constructionPoints
pointInput = constructionPoints.createInput()
pointInput.setByThreePlanes(planeX,planeY,planeZ)
constructionPoints.add(pointInput)
except:
if ui:
ui.messageBox('Failed:\n{}'.format(traceback.format_exc()))
Accepted solution
As Sebastian's code is pointing out, Fusion doesn't support creating a construction point at any location in space. Construction points are always associated to other geometry. The exception to this is when you're not capturing design history or when your working in a base feature. The code below creates a point at the center of gravity and uses a base feature to be able to position it at any location. I wanted to have the program create the point the first time you run it and them reposition it to the current COG each time you run it after that but I ran into a bug when I try to reposition it. I've logged it so we should have it fixed soon. I worked around it for now by deleting the existing point and re-creating it each time. The downside to this is if you build anything in relation to that point the relationship will be broken. Here's the code I ended up with. It has the workaround of deleting the point which results in the section of code that's currently crashing to never be called. Once the fix is made the delete code can be removed and then it should work as expected.
#Author-
#Description-
import adsk.core, adsk.fusion, adsk.cam, traceback
app = adsk.core.Application.get()
if app:
ui = app.userInterface
def run(context):
ui = None
try:
app = adsk.core.Application.get()
ui = app.userInterface
# Get all components in the active design.
product = app.activeProduct
design = adsk.fusion.Design.cast(product)
title = 'Create Center of Mass Point'
if not design:
ui.messageBox('No active Fusion design', title)
return
# Get the root component of the active design
rootComp = design.rootComponent
# Get physical properties from component (high accuracy)
physicalProperties = rootComp.getPhysicalProperties(adsk.fusion.CalculationAccuracy.HighCalculationAccuracy)
# Get center of mass from physical properties
cog = physicalProperties.centerOfMass
# Check to see if a base feature named "Center of Gravities" exists.
baseFeature = rootComp.features.itemByName('Center of Gravities')
if not baseFeature:
# Create a new base feature.
baseFeature = rootComp.features.baseFeatures.add()
baseFeature.name = 'Center of Gravities'
# Begin editing the base feature.
baseFeature.startEdit()
# Create a construction point at the COG position.
constructionPoints = rootComp.constructionPoints
pointInput = constructionPoints.createInput()
pointInput.setByPoint(cog)
pointInput.targetBaseOrFormFeature = baseFeature
constPoint = constructionPoints.add(pointInput)
constPoint.name = 'Center of Gravity'
# End the base feature edit.
baseFeature.finishEdit()
else:
# Check that the "Center of Gravity construction point exists.
cogPoint = rootComp.constructionPoints.itemByName('Center of Gravity')
# Because of a problem with updating an existing point, this current deletes
# the existing point so the code in the "else" is never executed.
if cogPoint:
cogPoint.deleteMe()
cogPoint = None
if not cogPoint:
# Create the construction point.
# Begin editing the base feature.
baseFeature.startEdit()
# Create a construction point at the COG position.
constructionPoints = rootComp.constructionPoints
pointInput = constructionPoints.createInput()
pointInput.setByPoint(cog)
pointInput.targetBaseOrFormFeature = baseFeature
constPoint = constructionPoints.add(pointInput)
constPoint.name = 'Center of Gravity'
# End the base feature edit.
baseFeature.finishEdit()
else:
# Edit the existing construction point.
pointDef = adsk.fusion.ConstructionPointPointDefinition.cast(cogPoint.definition)
baseFeature.startEdit()
pointDef.pointEntity = cog
baseFeature.finishEdit()
except:
if ui:
ui.messageBox('Failed:\n{}'.format(traceback.format_exc()))
Here's an updated version of what Sebastian wrote that creates the three construction planes to position the point. If the point already exists, it edits the parameter values controlling the planes to reposition the point.
def run(context):
try:
app = adsk.core.Application.get()
design = adsk.fusion.Design.cast(app.activeProduct)
rootComp = design.rootComponent
physicalProperties = rootComp.getPhysicalProperties(adsk.fusion.CalculationAccuracy.HighCalculationAccuracy)
cog = physicalProperties.centerOfMass
planes=rootComp.constructionPlanes
constPlane = planes.itemByName('Root COG X')
if not constPlane:
planeXInput = planes.createInput()
planeXInput.setByOffset(rootComp.yZConstructionPlane, adsk.core.ValueInput.createByReal(cog.x))
planeYInput = planes.createInput()
planeYInput.setByOffset(rootComp.xZConstructionPlane, adsk.core.ValueInput.createByReal(cog.y))
planeZInput = planes.createInput()
planeZInput.setByOffset(rootComp.xYConstructionPlane, adsk.core.ValueInput.createByReal(cog.z))
planeX = constPlane = planes.add(planeXInput)
constPlane.name = 'Root COG X'
constPlane.isVisible = False
planeY = constPlane = planes.add(planeYInput)
constPlane.name = 'Root COG Y'
constPlane.isVisible = False
planeZ = constPlane = planes.add(planeZInput)
constPlane.name = 'Root COG Z'
constPlane.isVisible = False
# Get construction points
constructionPoints = rootComp.constructionPoints
pointInput = constructionPoints.createInput()
pointInput.setByThreePlanes(planeX,planeY,planeZ)
constPoint = constructionPoints.add(pointInput)
constPoint.name = 'Center of Gravity'
else:
# Update the existing parameters.
cogConstPoint = rootComp.constructionPoints.itemByName('Center of Gravity')
pointDef = adsk.fusion.ConstructionPointThreePlanesDefinition.cast(cogConstPoint.definition)
planeX = pointDef.planeOne
planeY = pointDef.planeTwo
planeZ = pointDef.planeThree
planeDef = adsk.fusion.ConstructionPlaneOffsetDefinition.cast(planeX.definition)
planeDef.offset.value = cog.x
planeDef = adsk.fusion.ConstructionPlaneOffsetDefinition.cast(planeY.definition)
planeDef.offset.value = cog.y
planeDef = adsk.fusion.ConstructionPlaneOffsetDefinition.cast(planeZ.definition)
planeDef.offset.value = cog.z
except:
if ui:
ui.messageBox('Failed:\n{}'.format(traceback.format_exc()))
This is so awesome! It works!
Sebastian and Brian, thanks so much for your help. This is so useful for anyone who needs to do balancing applications.
Brian - I'm able to update the point by just rerunning the script. Delete / recreate doesn't appear to be necessary (at least in the cases I've been trying).
Very Best,
Mike
The program is automatically deleting and re-creating so there's nothing you need to do. It just has the bad side effect that if you associated something with the point, it will go sick because the point it's dependent on got deleted.
I'm not sure what you mean by "Did you cast it?".
Ohh, the comment was for MichaelAubry regarding the bird. I was asking about the fabrication method.
Incidentally - in addition to just the center of mass point, every body / component should just automatically have a «Moments of Inertia» (or similar) group that includes (1) the center of mass as an origin point, (2) any non-degenerate moments of inertia as direction vectors, and a plane when two of the moments of inertia are degenerate (because then any linear combination of those is also an eigenvector so the choice of a particular pair isn't unique)
It should look something like this when turned on:
where the center of mass is a point, the non-degenerate moment(s) are vector direction(s) like parts of an «origin» basis, and the degenerate vectors are a plane (the representation should be translated to center it at the center of mass.
All of those should be usable for defining geometry and relationships (like construction points, axes, and planes).
Just to extend the example of a top, this would be useful because it'd tell you not only where to put the center of rotation, but how to orient it, and how to properly balance it to avoid (or alternately induce) precession / nutation / wobbling / drift.
In an ideal top, the center of rotation would be at the center of mass with the axis of rotation aligned to a large, non-degenerate (unique) moment of inertia, and two smaller / degenerate moments of inertia would be in the plane of rotation
