Re: [Bf-committers] Cursor to center of mass
It's pretty easy to handle: http://www.pasteall.org/37405/python Am 21.11.2012 04:55, schrieb Brecht Van Lommel: Tessfaces includes both triangles and quads, it doesn't triangulate entirely, so you'd need to handle the quads still. Brecht. On Wed, Nov 21, 2012 at 4:30 AM, Ummi Nom ummi...@gmail.com wrote: Hi! I've written some center of mass calculations in python for closed meshes, but there is an issue with using tessfaces in my code; I run mesh.update with tessfaces=True but when I loop over mesh.tessfaces there are only 6 faces in default scene cube so the center of mass is offset. It seems to work when the mesh is triangulated http://www.pasteall.org/37396/python # Code import mathutils from mathutils import * import bpy tess_count = 0 # Handle tri as a tetrahedron with fourth point at origo def handleTri(v1, v2, v3): global tess_count tess_count = tess_count + 1 temp = (v3-v1).cross(v2-v1) nor = temp.normalized() area = 0.5*temp.dot(nor) vol = area*nor.dot(v1)/3.0 centroid = (v1+v2+v3)/4.0 return (centroid, vol) for me in bpy.data.meshes: me.update(calc_tessface=True) sumc= Vector() summ = 0 for f in me.tessfaces: v1 = Vector(me.vertices[f.vertices[0]].co) v2 = Vector(me.vertices[f.vertices[1]].co) v3 = Vector(me.vertices[f.vertices[2]].co) centroid, mass = handleTri(v1, v2, v3) sumc += centroid * mass summ += mass print(tess_count) print(sumc/summ) ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers
Re: [Bf-committers] Cursor to center of mass
Hey Jason, currently there is a problem with n-gons when chalculating the center of mass. The issue is that we don't have a good way of calculating centroids for n-gons and just use the vertex average, so the calculated origin will drift a little when your polygons have many vertices. I'd prefer to just tirangulate the model and use the triangle centroids but after a discussion with Campbell we decided it's not worth allocating a bunch of faces just to get a litte more accuracy. Regards, Sergej. Am Di, 20. Nov, 2012 um 12:12 ,Jason Wilkins jason.a.wilk...@gmail.com schrieb: Brecht, I figured that was what it did after testing it some, but since subdividing a face caused the center to move slightly I had my doubts. If it was vertexes I expected a really large move (since there were 100 times as many vertexes in my subdivided face than the rest of the model), but using faces or tets it should not move at all. Did I find a bug? On Mon, Nov 19, 2012 at 5:05 PM, Martin Bürbaum wrote: Just FYI - I did something similar (Snap Cursor to Centroid) as a script a while back. http://projects.blender.org/tracker/index.php?func=detailaid=30299group_id=153atid=467 Cheers, Martin Original-Nachricht Datum: Mon, 19 Nov 2012 19:00:23 -0300 Von: Juan Pablo Bouza An: bf-committers@blender.org Betreff: [Bf-committers] Cursor to center of mass Hi! The addition of the center of mass option for object origins is really cool! Now, there are many times in rigging when you need the center of the object to be at 0 0 0, specially for exporting meshes. So, in these cases, the origin to center of mass option would not be used. Nevertheless, the center of mass options would be really usefull for placing objects such as bones... So, I propose to add the center of mass option also in the Cursor snapping menu (shif+S). That would be cursor to center of mass. Cheers! ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers
Re: [Bf-committers] Cursor to center of mass
I can sort of see the reasoning behind that, but I would also argue accuracy can be very important. Maybe it'd be worth it to make a high quality operator bool in the same vein as the high quality normals in the Solidify modifier? -Patrick Date: Wed, 21 Nov 2012 17:36:19 +0001 From: sergej.re...@googlemail.com To: bf-committers@blender.org CC: bf-committers@blender.org Subject: Re: [Bf-committers] Cursor to center of mass Hey Jason, currently there is a problem with n-gons when chalculating the center of mass. The issue is that we don't have a good way of calculating centroids for n-gons and just use the vertex average, so the calculated origin will drift a little when your polygons have many vertices. I'd prefer to just tirangulate the model and use the triangle centroids but after a discussion with Campbell we decided it's not worth allocating a bunch of faces just to get a litte more accuracy. Regards, Sergej. Am Di, 20. Nov, 2012 um 12:12 ,Jason Wilkins jason.a.wilk...@gmail.com schrieb: Brecht, I figured that was what it did after testing it some, but since subdividing a face caused the center to move slightly I had my doubts. If it was vertexes I expected a really large move (since there were 100 times as many vertexes in my subdivided face than the rest of the model), but using faces or tets it should not move at all. Did I find a bug? On Mon, Nov 19, 2012 at 5:05 PM, Martin Bürbaum wrote: Just FYI - I did something similar (Snap Cursor to Centroid) as a script a while back. http://projects.blender.org/tracker/index.php?func=detailaid=30299group_id=153atid=467 Cheers, Martin Original-Nachricht Datum: Mon, 19 Nov 2012 19:00:23 -0300 Von: Juan Pablo Bouza An: bf-committers@blender.org Betreff: [Bf-committers] Cursor to center of mass Hi! The addition of the center of mass option for object origins is really cool! Now, there are many times in rigging when you need the center of the object to be at 0 0 0, specially for exporting meshes. So, in these cases, the origin to center of mass option would not be used. Nevertheless, the center of mass options would be really usefull for placing objects such as bones... So, I propose to add the center of mass option also in the Cursor snapping menu (shif+S). That would be cursor to center of mass. Cheers! ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers
Re: [Bf-committers] Cursor to center of mass
Oops, I forgot this was about the cursor snapping and had something else in
mind... My apologies. =)
From: p_boel...@msn.com
To: bf-committers@blender.org
Date: Wed, 21 Nov 2012 20:07:04 +0100
Subject: Re: [Bf-committers] Cursor to center of mass
I can sort of see the reasoning behind that, but I would also argue accuracy
can be very important. Maybe it'd be worth it to make a high quality
operator bool in the same vein as the high quality normals in the Solidify
modifier?
-Patrick
Date: Wed, 21 Nov 2012 17:36:19 +0001
From: sergej.re...@googlemail.com
To: bf-committers@blender.org
CC: bf-committers@blender.org
Subject: Re: [Bf-committers] Cursor to center of mass
Hey Jason,
currently there is a problem with n-gons when chalculating the center of
mass.
The issue is that we don't have a good way of calculating centroids for
n-gons and just use the vertex average, so the calculated origin will drift
a little when your polygons have many vertices.
I'd prefer to just tirangulate the model and use the triangle centroids but
after a discussion with Campbell we decided it's not worth allocating a
bunch of faces just to get a litte more accuracy.
Regards, Sergej.
Am Di, 20. Nov, 2012 um 12:12 ,Jason Wilkins jason.a.wilk...@gmail.com
schrieb:
Brecht, I figured that was what it did after testing it some, but
since subdividing a face caused the center to move slightly I had my
doubts. If it was vertexes I expected a really large move (since
there were 100 times as many vertexes in my subdivided face than the
rest of the model), but using faces or tets it should not move at all.
Did I find a bug?
On Mon, Nov 19, 2012 at 5:05 PM, Martin Bürbaum
wrote:
Just FYI - I did something similar (Snap Cursor to Centroid) as a
script a while back.
http://projects.blender.org/tracker/index.php?func=detailaid=30299group_id=153atid=467
Cheers,
Martin
Original-Nachricht
Datum: Mon, 19 Nov 2012 19:00:23 -0300
Von: Juan Pablo Bouza
An: bf-committers@blender.org
Betreff: [Bf-committers] Cursor to center of mass
Hi! The addition of the center of mass option for object origins is
really cool!
Now, there are many times in rigging when you need the center of the
object to be at 0 0 0, specially for exporting meshes. So, in these
cases, the origin to center of mass option would not be used.
Nevertheless, the center of mass options would be really usefull for
placing objects such as bones...
So, I propose to add the center of mass option also in the Cursor
snapping menu (shif+S). That would be cursor to center of mass.
Cheers!
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Re: [Bf-committers] Cursor to center of mass
Well, the calculation is used first to map the origin of the object
and this discussion was just how to extend that to moving the cursor.
As for it being because of n-gons, I do not think my model contained
n-gons. What I did was call the subdivide operator 4 times on one end
of the model, which created a bunch of new quads. Do quads count as
n-gons in this case?
I'll see if I can duplicate it and provide a .blend that narrows this
down if there is a problem.
On Wed, Nov 21, 2012 at 1:08 PM, patrick boelens p_boel...@msn.com wrote:
Oops, I forgot this was about the cursor snapping and had something else in
mind... My apologies. =)
From: p_boel...@msn.com
To: bf-committers@blender.org
Date: Wed, 21 Nov 2012 20:07:04 +0100
Subject: Re: [Bf-committers] Cursor to center of mass
I can sort of see the reasoning behind that, but I would also argue accuracy
can be very important. Maybe it'd be worth it to make a high quality
operator bool in the same vein as the high quality normals in the Solidify
modifier?
-Patrick
Date: Wed, 21 Nov 2012 17:36:19 +0001
From: sergej.re...@googlemail.com
To: bf-committers@blender.org
CC: bf-committers@blender.org
Subject: Re: [Bf-committers] Cursor to center of mass
Hey Jason,
currently there is a problem with n-gons when chalculating the center of
mass.
The issue is that we don't have a good way of calculating centroids for
n-gons and just use the vertex average, so the calculated origin will
drift a little when your polygons have many vertices.
I'd prefer to just tirangulate the model and use the triangle centroids
but after a discussion with Campbell we decided it's not worth allocating
a bunch of faces just to get a litte more accuracy.
Regards, Sergej.
Am Di, 20. Nov, 2012 um 12:12 ,Jason Wilkins jason.a.wilk...@gmail.com
schrieb:
Brecht, I figured that was what it did after testing it some, but
since subdividing a face caused the center to move slightly I had my
doubts. If it was vertexes I expected a really large move (since
there were 100 times as many vertexes in my subdivided face than the
rest of the model), but using faces or tets it should not move at all.
Did I find a bug?
On Mon, Nov 19, 2012 at 5:05 PM, Martin Bürbaum
wrote:
Just FYI - I did something similar (Snap Cursor to Centroid) as a
script a while back.
http://projects.blender.org/tracker/index.php?func=detailaid=30299group_id=153atid=467
Cheers,
Martin
Original-Nachricht
Datum: Mon, 19 Nov 2012 19:00:23 -0300
Von: Juan Pablo Bouza
An: bf-committers@blender.org
Betreff: [Bf-committers] Cursor to center of mass
Hi! The addition of the center of mass option for object origins is
really cool!
Now, there are many times in rigging when you need the center of the
object to be at 0 0 0, specially for exporting meshes. So, in these
cases, the origin to center of mass option would not be used.
Nevertheless, the center of mass options would be really usefull for
placing objects such as bones...
So, I propose to add the center of mass option also in the Cursor
snapping menu (shif+S). That would be cursor to center of mass.
Cheers!
___
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Re: [Bf-committers] Cursor to center of mass
Hi! I finished writing some testing code (only prints out the cm though). Planar convex/concave n-gon centroids should be correct and for closed meshes there's the tetrahedron stuff which uses either fake tris from polys or correct tris from tessfaces. Non-planar polys won't be correct because of the quick triangulation (v[0], v[i-1], v[i]) and because a flipped tri (vs polynormal) is always considered to have negative area. http://www.pasteall.org/37425/python On Thu, Nov 22, 2012 at 12:20 AM, Jason Wilkins jason.a.wilk...@gmail.comwrote: Well, the calculation is used first to map the origin of the object and this discussion was just how to extend that to moving the cursor. As for it being because of n-gons, I do not think my model contained n-gons. What I did was call the subdivide operator 4 times on one end of the model, which created a bunch of new quads. Do quads count as n-gons in this case? I'll see if I can duplicate it and provide a .blend that narrows this down if there is a problem. On Wed, Nov 21, 2012 at 1:08 PM, patrick boelens p_boel...@msn.com wrote: Oops, I forgot this was about the cursor snapping and had something else in mind... My apologies. =) From: p_boel...@msn.com To: bf-committers@blender.org Date: Wed, 21 Nov 2012 20:07:04 +0100 Subject: Re: [Bf-committers] Cursor to center of mass I can sort of see the reasoning behind that, but I would also argue accuracy can be very important. Maybe it'd be worth it to make a high quality operator bool in the same vein as the high quality normals in the Solidify modifier? -Patrick Date: Wed, 21 Nov 2012 17:36:19 +0001 From: sergej.re...@googlemail.com To: bf-committers@blender.org CC: bf-committers@blender.org Subject: Re: [Bf-committers] Cursor to center of mass Hey Jason, currently there is a problem with n-gons when chalculating the center of mass. The issue is that we don't have a good way of calculating centroids for n-gons and just use the vertex average, so the calculated origin will drift a little when your polygons have many vertices. I'd prefer to just tirangulate the model and use the triangle centroids but after a discussion with Campbell we decided it's not worth allocating a bunch of faces just to get a litte more accuracy. Regards, Sergej. Am Di, 20. Nov, 2012 um 12:12 ,Jason Wilkins jason.a.wilk...@gmail.com schrieb: Brecht, I figured that was what it did after testing it some, but since subdividing a face caused the center to move slightly I had my doubts. If it was vertexes I expected a really large move (since there were 100 times as many vertexes in my subdivided face than the rest of the model), but using faces or tets it should not move at all. Did I find a bug? On Mon, Nov 19, 2012 at 5:05 PM, Martin Bürbaum wrote: Just FYI - I did something similar (Snap Cursor to Centroid) as a script a while back. http://projects.blender.org/tracker/index.php?func=detailaid=30299group_id=153atid=467 Cheers, Martin Original-Nachricht Datum: Mon, 19 Nov 2012 19:00:23 -0300 Von: Juan Pablo Bouza An: bf-committers@blender.org Betreff: [Bf-committers] Cursor to center of mass Hi! The addition of the center of mass option for object origins is really cool! Now, there are many times in rigging when you need the center of the object to be at 0 0 0, specially for exporting meshes. So, in these cases, the origin to center of mass option would not be used. Nevertheless, the center of mass options would be really usefull for placing objects such as bones... So, I propose to add the center of mass option also in the Cursor snapping menu (shif+S). That would be cursor to center of mass. Cheers! ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers ___ Bf-committers mailing list Bf-committers@blender.org http
Re: [Bf-committers] Cursor to center of mass
Did you check against 'non orientable surfaces'? like Möbius strip Klein Bottle I doubt the algorithm stands with that... As far as I remember those objects have no defined volume? As : how would you like to make a cylinder from a Möbius strip? You can always create a bounding object .. like in triangulating the circle .. alas .. it will be getting close enough, which might be sufficient for blender, and might be nice to have.. Well if blender refuses to create such geometry .. bad enough Mathematica and friends can. Well I think you should check the definition of 'closed' and require 'orientable' and it will work out fine. so much for that BM one more .. your algorithm assumes homogeneous density .. how realistic is that ? .. for all cases ? Is a balloon filled with air the same as the balloon filled with water? As the mass is on the surface versus the mass is in the volume ? Am 21.11.2012 04:30, schrieb Ummi Nom: Hi! I've written some center of mass calculations in python for closed meshes, but there is an issue with using tessfaces in my code; I run mesh.update with tessfaces=True but when I loop over mesh.tessfaces there are only 6 faces in default scene cube so the center of mass is offset. It seems to work when the mesh is triangulated http://www.pasteall.org/37396/python # Code import mathutils from mathutils import * import bpy tess_count = 0 # Handle tri as a tetrahedron with fourth point at origo def handleTri(v1, v2, v3): global tess_count tess_count = tess_count + 1 temp = (v3-v1).cross(v2-v1) nor = temp.normalized() area = 0.5*temp.dot(nor) vol = area*nor.dot(v1)/3.0 centroid = (v1+v2+v3)/4.0 return (centroid, vol) for me in bpy.data.meshes: me.update(calc_tessface=True) sumc= Vector() summ = 0 for f in me.tessfaces: v1 = Vector(me.vertices[f.vertices[0]].co) v2 = Vector(me.vertices[f.vertices[1]].co) v3 = Vector(me.vertices[f.vertices[2]].co) centroid, mass = handleTri(v1, v2, v3) sumc += centroid * mass summ += mass print(tess_count) print(sumc/summ) ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers
Re: [Bf-committers] Cursor to center of mass
Every algorithm has it's limitations. Computing the center of mass for a body that has no volume is a quite useless task and assuming inhomogeneous density for a body that is only defined by the surface is also questionable. For the average case a closed surface and the assumption of homogeneity is already sufficient enough. For anything else you could play around with shrinkwrap or something else to create a hull that approximates the volume. Regarding the balloon. It doesn't matter in this case if the mass is centred at the surface or inside the volume. The result for the center of mass is still the same. It would only matter if you had a balloon filled half with water and half air. Am 22.11.2012 02:46, schrieb bjornm...@gmx.net: Did you check against 'non orientable surfaces'? like Möbius strip Klein Bottle I doubt the algorithm stands with that... As far as I remember those objects have no defined volume? As : how would you like to make a cylinder from a Möbius strip? You can always create a bounding object .. like in triangulating the circle .. alas .. it will be getting close enough, which might be sufficient for blender, and might be nice to have.. Well if blender refuses to create such geometry .. bad enough Mathematica and friends can. Well I think you should check the definition of 'closed' and require 'orientable' and it will work out fine. so much for that BM one more .. your algorithm assumes homogeneous density .. how realistic is that ? .. for all cases ? Is a balloon filled with air the same as the balloon filled with water? As the mass is on the surface versus the mass is in the volume ? Am 21.11.2012 04:30, schrieb Ummi Nom: Hi! I've written some center of mass calculations in python for closed meshes, but there is an issue with using tessfaces in my code; I run mesh.update with tessfaces=True but when I loop over mesh.tessfaces there are only 6 faces in default scene cube so the center of mass is offset. It seems to work when the mesh is triangulated http://www.pasteall.org/37396/python # Code import mathutils from mathutils import * import bpy tess_count = 0 # Handle tri as a tetrahedron with fourth point at origo def handleTri(v1, v2, v3): global tess_count tess_count = tess_count + 1 temp = (v3-v1).cross(v2-v1) nor = temp.normalized() area = 0.5*temp.dot(nor) vol = area*nor.dot(v1)/3.0 centroid = (v1+v2+v3)/4.0 return (centroid, vol) for me in bpy.data.meshes: me.update(calc_tessface=True) sumc= Vector() summ = 0 for f in me.tessfaces: v1 = Vector(me.vertices[f.vertices[0]].co) v2 = Vector(me.vertices[f.vertices[1]].co) v3 = Vector(me.vertices[f.vertices[2]].co) centroid, mass = handleTri(v1, v2, v3) sumc += centroid * mass summ += mass print(tess_count) print(sumc/summ) ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers
Re: [Bf-committers] Cursor to center of mass
Hi! I'm aiming a bit lower so I prefer to attack the mechanics of the problem. Limiting the calculation by actual volume to when it makes sense would be nice, but detecting overlaps etc. seems overkill. Here's later code which does it basically two ways, one is the tetrahedron and the other is polygon centroid. http://www.pasteall.org/37425/python On Thu, Nov 22, 2012 at 3:46 AM, bjornm...@gmx.net bjornm...@gmx.netwrote: Did you check against 'non orientable surfaces'? like Möbius strip Klein Bottle I doubt the algorithm stands with that... As far as I remember those objects have no defined volume? As : how would you like to make a cylinder from a Möbius strip? You can always create a bounding object .. like in triangulating the circle .. alas .. it will be getting close enough, which might be sufficient for blender, and might be nice to have.. Well if blender refuses to create such geometry .. bad enough Mathematica and friends can. Well I think you should check the definition of 'closed' and require 'orientable' and it will work out fine. so much for that BM one more .. your algorithm assumes homogeneous density .. how realistic is that ? .. for all cases ? Is a balloon filled with air the same as the balloon filled with water? As the mass is on the surface versus the mass is in the volume ? Am 21.11.2012 04:30, schrieb Ummi Nom: Hi! I've written some center of mass calculations in python for closed meshes, but there is an issue with using tessfaces in my code; I run mesh.update with tessfaces=True but when I loop over mesh.tessfaces there are only 6 faces in default scene cube so the center of mass is offset. It seems to work when the mesh is triangulated http://www.pasteall.org/37396/python # Code import mathutils from mathutils import * import bpy tess_count = 0 # Handle tri as a tetrahedron with fourth point at origo def handleTri(v1, v2, v3): global tess_count tess_count = tess_count + 1 temp = (v3-v1).cross(v2-v1) nor = temp.normalized() area = 0.5*temp.dot(nor) vol = area*nor.dot(v1)/3.0 centroid = (v1+v2+v3)/4.0 return (centroid, vol) for me in bpy.data.meshes: me.update(calc_tessface=True) sumc= Vector() summ = 0 for f in me.tessfaces: v1 = Vector(me.vertices[f.vertices[0]].co) v2 = Vector(me.vertices[f.vertices[1]].co) v3 = Vector(me.vertices[f.vertices[2]].co) centroid, mass = handleTri(v1, v2, v3) sumc += centroid * mass summ += mass print(tess_count) print(sumc/summ) ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers
Re: [Bf-committers] Cursor to center of mass
Actually, subdivide creates n-gons in most cases (unless you use it on edge
rings or the whole mesh), so it's likely to be the problem.
Also here is a quick patch that adds a Cursor to Center of Mass option:
http://www.pasteall.org/37435/diff
Am Mi, 21. Nov, 2012 um 11:20 ,Jason Wilkins jason.a.wilk...@gmail.com
schrieb:
Well, the calculation is used first to map the origin of the object
and this discussion was just how to extend that to moving the cursor.
As for it being because of n-gons, I do not think my model contained
n-gons. What I did was call the subdivide operator 4 times on one end
of the model, which created a bunch of new quads. Do quads count as
n-gons in this case?
I'll see if I can duplicate it and provide a .blend that narrows this
down if there is a problem.
On Wed, Nov 21, 2012 at 1:08 PM, patrick boelens wrote:
Oops, I forgot this was about the cursor snapping and had something else in
mind... My apologies. =)
From: p_boel...@msn.com
To: bf-committers@blender.org
Date: Wed, 21 Nov 2012 20:07:04 +0100
Subject: Re: [Bf-committers] Cursor to center of mass
I can sort of see the reasoning behind that, but I would also argue accuracy
can be very important. Maybe it'd be worth it to make a high quality
operator bool in the same vein as the high quality normals in the Solidify
modifier?
-Patrick
Date: Wed, 21 Nov 2012 17:36:19 +0001
From: sergej.re...@googlemail.com
To: bf-committers@blender.org
CC: bf-committers@blender.org
Subject: Re: [Bf-committers] Cursor to center of mass
Hey Jason,
currently there is a problem with n-gons when chalculating the center of
mass.
The issue is that we don't have a good way of calculating centroids for
n-gons and just use the vertex average, so the calculated origin will
drift a little when your polygons have many vertices.
I'd prefer to just tirangulate the model and use the triangle centroids
but after a discussion with Campbell we decided it's not worth allocating
a bunch of faces just to get a litte more accuracy.
Regards, Sergej.
Am Di, 20. Nov, 2012 um 12:12 ,Jason Wilkins schrieb:
Brecht, I figured that was what it did after testing it some, but
since subdividing a face caused the center to move slightly I had my
doubts. If it was vertexes I expected a really large move (since
there were 100 times as many vertexes in my subdivided face than the
rest of the model), but using faces or tets it should not move at all.
Did I find a bug?
On Mon, Nov 19, 2012 at 5:05 PM, Martin Bürbaum
wrote:
Just FYI - I did something similar (Snap Cursor to Centroid) as a
script a while back.
http://projects.blender.org/tracker/index.php?func=detailaid=30299group_id=153atid=467
Cheers,
Martin
Original-Nachricht
Datum: Mon, 19 Nov 2012 19:00:23 -0300
Von: Juan Pablo Bouza
An: bf-committers@blender.org
Betreff: [Bf-committers] Cursor to center of mass
Hi! The addition of the center of mass option for object origins is
really cool!
Now, there are many times in rigging when you need the center of the
object to be at 0 0 0, specially for exporting meshes. So, in these
cases, the origin to center of mass option would not be used.
Nevertheless, the center of mass options would be really usefull for
placing objects such as bones...
So, I propose to add the center of mass option also in the Cursor
snapping menu (shif+S). That would be cursor to center of mass.
Cheers!
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[Bf-committers] Cursor to center of mass
Hi! I've written some center of mass calculations in python for closed meshes, but there is an issue with using tessfaces in my code; I run mesh.update with tessfaces=True but when I loop over mesh.tessfaces there are only 6 faces in default scene cube so the center of mass is offset. It seems to work when the mesh is triangulated http://www.pasteall.org/37396/python # Code import mathutils from mathutils import * import bpy tess_count = 0 # Handle tri as a tetrahedron with fourth point at origo def handleTri(v1, v2, v3): global tess_count tess_count = tess_count + 1 temp = (v3-v1).cross(v2-v1) nor = temp.normalized() area = 0.5*temp.dot(nor) vol = area*nor.dot(v1)/3.0 centroid = (v1+v2+v3)/4.0 return (centroid, vol) for me in bpy.data.meshes: me.update(calc_tessface=True) sumc= Vector() summ = 0 for f in me.tessfaces: v1 = Vector(me.vertices[f.vertices[0]].co) v2 = Vector(me.vertices[f.vertices[1]].co) v3 = Vector(me.vertices[f.vertices[2]].co) centroid, mass = handleTri(v1, v2, v3) sumc += centroid * mass summ += mass print(tess_count) print(sumc/summ) ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers
Re: [Bf-committers] Cursor to center of mass
Tessfaces includes both triangles and quads, it doesn't triangulate entirely, so you'd need to handle the quads still. Brecht. On Wed, Nov 21, 2012 at 4:30 AM, Ummi Nom ummi...@gmail.com wrote: Hi! I've written some center of mass calculations in python for closed meshes, but there is an issue with using tessfaces in my code; I run mesh.update with tessfaces=True but when I loop over mesh.tessfaces there are only 6 faces in default scene cube so the center of mass is offset. It seems to work when the mesh is triangulated http://www.pasteall.org/37396/python # Code import mathutils from mathutils import * import bpy tess_count = 0 # Handle tri as a tetrahedron with fourth point at origo def handleTri(v1, v2, v3): global tess_count tess_count = tess_count + 1 temp = (v3-v1).cross(v2-v1) nor = temp.normalized() area = 0.5*temp.dot(nor) vol = area*nor.dot(v1)/3.0 centroid = (v1+v2+v3)/4.0 return (centroid, vol) for me in bpy.data.meshes: me.update(calc_tessface=True) sumc= Vector() summ = 0 for f in me.tessfaces: v1 = Vector(me.vertices[f.vertices[0]].co) v2 = Vector(me.vertices[f.vertices[1]].co) v3 = Vector(me.vertices[f.vertices[2]].co) centroid, mass = handleTri(v1, v2, v3) sumc += centroid * mass summ += mass print(tess_count) print(sumc/summ) ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers
[Bf-committers] Cursor to center of mass
Hi! The addition of the center of mass option for object origins is really cool! Now, there are many times in rigging when you need the center of the object to be at 0 0 0, specially for exporting meshes. So, in these cases, the origin to center of mass option would not be used. Nevertheless, the center of mass options would be really usefull for placing objects such as bones... So, I propose to add the center of mass option also in the Cursor snapping menu (shif+S). That would be cursor to center of mass. Cheers! ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers
Re: [Bf-committers] Cursor to center of mass
I'll ask, since I hope it will save time instead of looking at the code. Is the center of mass option actually calculating a center of mass or is it calculating a centroid? A centroid would be equivalent to the center of mass of a set of equally massive points at the vertexes. A true center of mass would require some kind of tetrahedralization and integration over the interior mass of an object. That seems quite heavy duty so that is why I'm having doubts that this feature is named correctly. On Mon, Nov 19, 2012 at 4:00 PM, Juan Pablo Bouza jpbo...@hotmail.com wrote: Hi! The addition of the center of mass option for object origins is really cool! Now, there are many times in rigging when you need the center of the object to be at 0 0 0, specially for exporting meshes. So, in these cases, the origin to center of mass option would not be used. Nevertheless, the center of mass options would be really usefull for placing objects such as bones... So, I propose to add the center of mass option also in the Cursor snapping menu (shif+S). That would be cursor to center of mass. Cheers! ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers
Re: [Bf-committers] Cursor to center of mass
I did some experiments and it does seem to work quite well, whatever method is used. If nobody else wants to look at adding a cursor to center of mass option for placing the 3D cursor then I'll do it. On Mon, Nov 19, 2012 at 4:00 PM, Juan Pablo Bouza jpbo...@hotmail.com wrote: Hi! The addition of the center of mass option for object origins is really cool! Now, there are many times in rigging when you need the center of the object to be at 0 0 0, specially for exporting meshes. So, in these cases, the origin to center of mass option would not be used. Nevertheless, the center of mass options would be really usefull for placing objects such as bones... So, I propose to add the center of mass option also in the Cursor snapping menu (shif+S). That would be cursor to center of mass. Cheers! ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers
Re: [Bf-committers] Cursor to center of mass
It's based on face areas, so it could be interpreted as the center of mass of a hollow object. Brecht. On Mon, Nov 19, 2012 at 11:37 PM, Jason Wilkins jason.a.wilk...@gmail.com wrote: I did some experiments and it does seem to work quite well, whatever method is used. If nobody else wants to look at adding a cursor to center of mass option for placing the 3D cursor then I'll do it. On Mon, Nov 19, 2012 at 4:00 PM, Juan Pablo Bouza jpbo...@hotmail.com wrote: Hi! The addition of the center of mass option for object origins is really cool! Now, there are many times in rigging when you need the center of the object to be at 0 0 0, specially for exporting meshes. So, in these cases, the origin to center of mass option would not be used. Nevertheless, the center of mass options would be really usefull for placing objects such as bones... So, I propose to add the center of mass option also in the Cursor snapping menu (shif+S). That would be cursor to center of mass. Cheers! ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers
Re: [Bf-committers] Cursor to center of mass
Just FYI - I did something similar (Snap Cursor to Centroid) as a script a while back. http://projects.blender.org/tracker/index.php?func=detailaid=30299group_id=153atid=467 Cheers, Martin Original-Nachricht Datum: Mon, 19 Nov 2012 19:00:23 -0300 Von: Juan Pablo Bouza jpbo...@hotmail.com An: bf-committers@blender.org Betreff: [Bf-committers] Cursor to center of mass Hi! The addition of the center of mass option for object origins is really cool! Now, there are many times in rigging when you need the center of the object to be at 0 0 0, specially for exporting meshes. So, in these cases, the origin to center of mass option would not be used. Nevertheless, the center of mass options would be really usefull for placing objects such as bones... So, I propose to add the center of mass option also in the Cursor snapping menu (shif+S). That would be cursor to center of mass. Cheers! ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers
Re: [Bf-committers] Cursor to center of mass
Brecht, I figured that was what it did after testing it some, but since subdividing a face caused the center to move slightly I had my doubts. If it was vertexes I expected a really large move (since there were 100 times as many vertexes in my subdivided face than the rest of the model), but using faces or tets it should not move at all. Did I find a bug? On Mon, Nov 19, 2012 at 5:05 PM, Martin Bürbaum martin.buerb...@gmx.at wrote: Just FYI - I did something similar (Snap Cursor to Centroid) as a script a while back. http://projects.blender.org/tracker/index.php?func=detailaid=30299group_id=153atid=467 Cheers, Martin Original-Nachricht Datum: Mon, 19 Nov 2012 19:00:23 -0300 Von: Juan Pablo Bouza jpbo...@hotmail.com An: bf-committers@blender.org Betreff: [Bf-committers] Cursor to center of mass Hi! The addition of the center of mass option for object origins is really cool! Now, there are many times in rigging when you need the center of the object to be at 0 0 0, specially for exporting meshes. So, in these cases, the origin to center of mass option would not be used. Nevertheless, the center of mass options would be really usefull for placing objects such as bones... So, I propose to add the center of mass option also in the Cursor snapping menu (shif+S). That would be cursor to center of mass. Cheers! ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers
Re: [Bf-committers] Cursor to center of mass
Thanks for looking into this guys! You're the best :D Date: Mon, 19 Nov 2012 17:12:00 -0600 From: jason.a.wilk...@gmail.com To: bf-committers@blender.org Subject: Re: [Bf-committers] Cursor to center of mass Brecht, I figured that was what it did after testing it some, but since subdividing a face caused the center to move slightly I had my doubts. If it was vertexes I expected a really large move (since there were 100 times as many vertexes in my subdivided face than the rest of the model), but using faces or tets it should not move at all. Did I find a bug? On Mon, Nov 19, 2012 at 5:05 PM, Martin Bürbaum martin.buerb...@gmx.at wrote: Just FYI - I did something similar (Snap Cursor to Centroid) as a script a while back. http://projects.blender.org/tracker/index.php?func=detailaid=30299group_id=153atid=467 Cheers, Martin Original-Nachricht Datum: Mon, 19 Nov 2012 19:00:23 -0300 Von: Juan Pablo Bouza jpbo...@hotmail.com An: bf-committers@blender.org Betreff: [Bf-committers] Cursor to center of mass Hi! The addition of the center of mass option for object origins is really cool! Now, there are many times in rigging when you need the center of the object to be at 0 0 0, specially for exporting meshes. So, in these cases, the origin to center of mass option would not be used. Nevertheless, the center of mass options would be really usefull for placing objects such as bones... So, I propose to add the center of mass option also in the Cursor snapping menu (shif+S). That would be cursor to center of mass. Cheers! ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers ___ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers
