m*****o
发帖数: 17 | 1 Dear all,
I have a basic question about the parametric surface. I have a set of
unstructured 3D points acquired by a scanner. A coarse mesh was generated
based on the geometry of the subject that was scanned. Now I want to get a
parametric representation of the surface, but some global fitting is needed
since the data is too noisy.
From my understanding, the global fitting can be achieved by filtering along
u direction and v direction separately and sequentially. Please correct me
if I'm wrong h | r***l
发帖数: 36 | 2 don't do filtering seperately along two directions.
google for mean curvature flow, it can be done without parameterization.
you can also look for modified version of it, which can keep features better,
especially since your shape is tube-like, it means the two principal
curvatures
are quite different (one being almost 0), so you have to take the
anisotropy into account. there are quite some papers on this.
needed
along
me
and
【在 m*****o 的大作中提到】
: Dear all,
: I have a basic question about the parametric surface. I have a set of
: unstructured 3D points acquired by a scanner. A coarse mesh was generated
: based on the geometry of the subject that was scanned. Now I want to get a
: parametric representation of the surface, but some global fitting is needed
: since the data is too noisy.
: From my understanding, the global fitting can be achieved by filtering along
: u direction and v direction separately and sequentially. Please correct me
: if I'm wrong h
| m*****o
发帖数: 17 | 3 Hi,romel, thanks a lot for your suggestion. I guess the mean curvature flow
you suggested is level-set method related implicit surface. If my guess were
right, would the speed very slow? Thanks again.
better,
【在 r***l 的大作中提到】
: don't do filtering seperately along two directions.
: google for mean curvature flow, it can be done without parameterization.
: you can also look for modified version of it, which can keep features better,
: especially since your shape is tube-like, it means the two principal
: curvatures
: are quite different (one being almost 0), so you have to take the
: anisotropy into account. there are quite some papers on this.
:
: needed
: along
| r***l
发帖数: 36 | 4 what I was suggesting is mesh-based, but level set doesn't have to be slow
either.
It is indeed an iterative method, but it's not slow.
What you need to compute is a gradient flow, the graident of total surface
area, and on a surface, it means the vertex needs to follow (1/A_x)dA/dx,
you should be able to find the details for mean curvature flow on meshes.
flow
were
【在 m*****o 的大作中提到】
: Hi,romel, thanks a lot for your suggestion. I guess the mean curvature flow
: you suggested is level-set method related implicit surface. If my guess were
: right, would the speed very slow? Thanks again.
:
: better,
| m*****o
发帖数: 17 | 5 Hi, Romel, I really appreciate your input. Actually I didn't expect we could
find very detailed suggestions like yours on this board, and yours just
gave us some insights. Here I have some detailed questions. My apologies
that I asked too many questions and occupied you a lot of time. I'm not a
graphics guy and nobody in my group knows too much about it either, but we
have to do something in graphics to keep our jobs. :(
I believe mesh-based algorithm could be very fast, since we've done some
al
【在 r***l 的大作中提到】
: what I was suggesting is mesh-based, but level set doesn't have to be slow
: either.
: It is indeed an iterative method, but it's not slow.
: What you need to compute is a gradient flow, the graident of total surface
: area, and on a surface, it means the vertex needs to follow (1/A_x)dA/dx,
: you should be able to find the details for mean curvature flow on meshes.
:
: flow
: were
| r***l
发帖数: 36 | 6 http://www.multires.caltech.edu/pubs/gi2000.pdf
this is an old one, but should be ok.
try equation (13) for \nabla A
for area of a vertex take 1/3 of the area of triangles adjacent to the
vertex.
basically, you add this - \nabla A/A * dt to X_i iteratively, you can do
implicit integration too. but if you take a small dt, explicit method should
be ok too.
could
calculate
for
【在 m*****o 的大作中提到】
: Hi, Romel, I really appreciate your input. Actually I didn't expect we could
: find very detailed suggestions like yours on this board, and yours just
: gave us some insights. Here I have some detailed questions. My apologies
: that I asked too many questions and occupied you a lot of time. I'm not a
: graphics guy and nobody in my group knows too much about it either, but we
: have to do something in graphics to keep our jobs. :(
: I believe mesh-based algorithm could be very fast, since we've done some
: al
| m*****o
发帖数: 17 | 7 Hi, Romel, thanks a lot for the paper and your detailed suggestions. I'll
take a look at it. Take care.
Regards,
MRITRIO
should
【在 r***l 的大作中提到】
: http://www.multires.caltech.edu/pubs/gi2000.pdf
: this is an old one, but should be ok.
: try equation (13) for \nabla A
: for area of a vertex take 1/3 of the area of triangles adjacent to the
: vertex.
: basically, you add this - \nabla A/A * dt to X_i iteratively, you can do
: implicit integration too. but if you take a small dt, explicit method should
: be ok too.
:
: could
|
|
