VolumeCentroid Won’t work with curves.
Is there a script or option to get it work based on bounding box. Thanks
The Gumball center should be the bb center of selected curves… Or make a bounding box and use volume centroid on that.
Hi Mitch thank you for writing on this.
I mean a command that would create VolumeCentroids despite the object as with planar curves this approach would not work.
Just a Center/Centroid function for all — no concept of Area Centroid or Volume Centroid - just automatic based on context.
Thank you
The problem is that all of these are potentially different.
A closed surface/polysurface can have
- a volume centroid
- an area centroid
- a bounding box center
All three of those can be different points.
An open surface/polysurface can have
- an area centroid
- a bounding box center
Both of those can be different points.
An planar curve can have
- an area centroid
- a bounding box center
And if it is a polyline it can also have - the average of its vertices
- the average of its edges
All of those can be different points.
An arbitrary 3D curve can have
- a bounding box center
So you can see that the only one that is common to all of the above is the bounding box center - which is what Gumball uses. And for the objects that have multiple possibilities - practically all of the above - which method should Rhino choose?
Edit - if you want a simple script you can put on an alias to create a point at selected objects’ bounding box center, here you go:
import rhinoscriptsyntax as rs
obj_ids=rs.GetObjects("Select objects for bounding box centroid",preselect=True)
if obj_ids:
bb=rs.BoundingBox(obj_ids)
if bb: rs.AddPoint((bb[0]+bb[6])/2)
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Mitch! So good, we have to mention for newbies to take the script data and paste them into a text file and name it ObjectCentroid.py and move it into the scripts folder and bind an Alias to it as OC
Thanks a lot for this works like a charm!
Well, there are a number of ways to install and run scripts:
https://wiki.mcneel.com/rhino/macroscriptsetup
Well, that might be a bit of a misnomer, as it doesn’t find the object centroid, it only finds the bounding box center (as mentioned above).
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Hey Mitch, as always — sharp as a katana.
Hi everyone,
Does someone know why you can’t properly compute the Boundingbox’s center of a block or of an object if it is inside a block? Is this a new Rhino8 issue?
For example: below is a snapshot from a file with circles in blocks and outside of blocks. The centroids are incorrectly placed for the blocks and the objects inside blocks. You can see the 4 centroid (2 blocks + 2 circles in the blocks) floating near the World origin. The “free” circles have correct centroid dots.
Below is the script I used:
#! python 3
import rhinoscriptsyntax as rs
def loopBlock(block):
objectsInBlock = rs.BlockObjects(rs.BlockInstanceName(block))
for obj in objectsInBlock:
if rs.ObjectType(obj) != 4096:
action(obj)
else:
loopBlock(obj)
def action(object):
bb=rs.BoundingBox(object)
if bb: center = (bb[0]+bb[6])/2
rs.AddTextDot("Centroid!",center)
objs = rs.AllObjects(include_lights=False, include_grips=False)
if objs:
for obj in objs:
if rs.ObjectType(obj) == 4096: #block
loopBlock(obj)
else:
action(obj)
else:
print("No objects selectable.")
rs.Redraw()
The test file is attached.
testfile_centroid.3dm (2.6 MB)
I suspect because the centroids are calculated based on the positions of the original objects in the block, not of the individual instances - which may have been moved. For each instance you will probably need to transform the centroid points based on the block instance transformation.
Thanks for the hint, I had that in mind too. I managed to make it work by gradually adding all the block instances transformation data to the centroid of the bounding box. It’s a bit tedious, but it works.
Here’s the complete script, for future reference:
#! python 3
import rhinoscriptsyntax as rs
import Rhino
def dotIt(centroid):
rs.AddTextDot("Centroid!",centroid)
def getBlockOrigin(block):
irefObj = rs.coercerhinoobject(block)
idef = irefObj.InstanceDefinition
blockOrigin = irefObj.InsertionPoint
return blockOrigin
def getCentroid(obj): #cannot be directly applied to a block
bb=rs.BoundingBox(obj)
if bb:
centroid = ((bb[0]+bb[6])/2)
return centroid
def loopBlock(block, origin):
blockOrigin = getBlockOrigin(block) + origin
blockCentroid = origin + getCentroid(block)
dotIt(blockCentroid)
objectsInBlock = rs.BlockObjects(rs.BlockInstanceName(block))
for obj in objectsInBlock:
if rs.ObjectType(obj) != 4096: #is not a block
objCentroid = blockOrigin + getCentroid(obj)
dotIt(objCentroid)
else:
loopBlock(obj, blockOrigin)
objs = rs.AllObjects(include_lights=False, include_grips=False)
if objs:
for obj in objs:
if rs.ObjectType(obj) == 4096: #is a block
loopBlock(obj, Rhino.Geometry.Point3d.Origin)
else:
dotIt(getCentroid(obj))
else:
print("Could not select all objects.")
rs.Redraw()