215 research outputs found
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Modelling oedemous limbs and venous ulcers using partial differential equations
Background
Oedema, commonly known as tissue swelling, occurs mainly on the leg and the arm. The condition may be associated with a range of causes such as venous diseases, trauma, infection, joint disease and orthopaedic surgery. Oedema is caused by both lymphatic and chronic venous insufficiency, which leads to pooling of blood and fluid in the extremities. This results in swelling, mild redness and scaling of the skin, all of which can culminate in ulceration.
Methods
We present a method to model a wide variety of geometries of limbs affected by oedema and venous ulcers. The shape modelling is based on the PDE method where a set of boundary curves are extracted from 3D scan data and are utilised as boundary conditions to solve a PDE, which provides the geometry of an affected limb. For this work we utilise a mixture of fourth order and sixth order PDEs, the solutions of which enable us to obtain a good representative shape of the limb and associated ulcers in question.
Results
A series of examples are discussed demonstrating the capability of the method to produce good representative shapes of limbs by utilising a series of curves extracted from the scan data. In particular we show how the method could be used to model the shape of an arm and a leg with an associated ulcer.
Conclusion
We show how PDE based shape modelling techniques can be utilised to generate a variety of limb shapes and associated ulcers by means of a series of curves extracted from scan data. We also discuss how the method could be used to manipulate a generic shape of a limb and an associated wound so that the model could be fine-tuned for a particular patient
Modelling of oedemous limbs and venous ulcers using partial differential equations
BACKGROUND:
Oedema, commonly known as tissue swelling, occurs mainly on the leg and the arm. The condition may be associated with a range of causes such as venous diseases, trauma, infection, joint disease and orthopaedic surgery. Oedema is caused by both lymphatic and chronic venous insufficiency, which leads to pooling of blood and fluid in the extremities. This results in swelling, mild redness and scaling of the skin, all of which can culminate in ulceration.
METHODS:
We present a method to model a wide variety of geometries of limbs affected by oedema and venous ulcers. The shape modelling is based on the PDE method where a set of boundary curves are extracted from 3D scan data and are utilised as boundary conditions to solve a PDE, which provides the geometry of an affected limb. For this work we utilise a mixture of fourth order and sixth order PDEs, the solutions of which enable us to obtain a good representative shape of the limb and associated ulcers in question.
RESULTS:
A series of examples are discussed demonstrating the capability of the method to produce good representative shapes of limbs by utilising a series of curves extracted from the scan data. In particular we show how the method could be used to model the shape of an arm and a leg with an associated ulcer.
CONCLUSION:
We show how PDE based shape modelling techniques can be utilised to generate a variety of limb shapes and associated ulcers by means of a series of curves extracted from scan data. We also discuss how the method could be used to manipulate a generic shape of a limb and an associated wound so that the model could be fine-tuned for a particular patient
Spine based shape parameterisation for PDE surfaces
The aim of this paper is to show how the spine of a PDE surface can be generated and how it can be used to efficiently parameterise a PDE surface. For the purpose of the work presented here an approximate analytic solution form for the chosen PDE is utilised. It is shown that the spine of the PDE surface is then computed as a by-product of this analytic solution. Furthermore, it is shown that a parameterisation can be introduced on the spine enabling intuitive manipulation of PDE surfaces
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3D facial data fitting using the biharmonic equation
This paper discusses how a boundary-based surface fitting approach can be utilised to smoothly reconstruct a given human face where the scan data corresponding to the face is provided. In particular, the paper discusses how a solution to the Biharmonic equation can be used to set up the corresponding boundary value problem. We show how a compact explicit solution method can be utilised for efficiently solving the chosen Biharmonic equation.
Thus, given the raw scan data of a 3D face, we extract a series of profile curves from the data which can then be utilised as boundary conditions to solve the Biharmonic equation. The resulting solution provides us a continuous single surface patch describing the original face
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Computation of curvatures over discrete geometry using biharmonic surfaces
The computation of curvature quantities over discrete geometry is often required when processing geometry composed of meshes. Curvature information is often important for the purpose of shape analysis, feature recognition and geometry segmentation. In this paper we present a method for accurate estimation of curvature on discrete geometry especially those composed of meshes. We utilise a method based on fitting a continuous surface arising from the solution of the Biharmonic equation subject to suitable boundary conditions over a 1-ring neighbourhood of the mesh geometry model. This enables us to accurately determine the curvature distribution of the local area. We show how the curvature can be computed efficiently by means of utilising an analytic solution representation of the chosen Biharmonic equation. In order to demonstrate the method we present a series of examples whereby we show how the curvature can be efficiently computed over complex geometry which are represented discretely by means of mesh models
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Parametric surface meshing for design optimisation using a PDE formulation
yesThe problem of parametric surface meshing for the purpose of design optimisation using finite element analysis is considered. Here the surface mesh is generated as a solution of a suitably posed boundary value problem implemented on a 2D parameter space. A robust meshing scheme is presented where an initial mesh is manipulated, with the aid of the 2D parameter space, so as to obtain a suitable surface triangulation. This meshing scheme can then be used to create suitable finite element meshes with which accurate design optimisations can be carried out
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Method of boundary based smooth shape design
The discussion in this paper focuses on how boundary
based smooth shape design can be carried out. For this we
treat surface generation as a mathematical boundary-value
problem. In particular, we utilize elliptic Partial Differential
Equations (PDEs) of arbitrary order. Using the methodology
outlined here a designer can therefore generate the
geometry of shapes satisfying an arbitrary set of boundary
conditions. The boundary conditions for the chosen PDE
can be specified as curves in 3-space defining the profile
geometry of the shape.
We show how a compact analytic solution for the chosen
arbitrary order PDE can be formulated enabling complex
shapes to be designed and manipulated in real time.
This solution scheme, although analytic, satisfies exactly,
even in the case of general boundary conditions, where the
resulting surface has a closed form representation allowing
real time shape manipulation. In order to enable users
to appreciate the powerful shape design and manipulation
capability of the method, we present a set of practical example
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3D data modelling and processing using partial differential equations.
NoIn this paper we discuss techniques for 3D
data modelling and processing where the data are
usually provided as point clouds which arise from 3D
scanning devices. The particular approaches we adopt
in modelling 3D data involves the use of Partial
Differential Equations (PDEs). In particular we show
how the continuous and discrete versions of elliptic
PDEs can be used for data modelling. We show that
using PDEs it is intuitively possible to model data
corresponding to complex scenes. Furthermore, we
show that data can be stored in compact format in the
form of PDE boundary conditions. In order to
demonstrate the methodology we utlise several examples
of practical nature
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Parametric Representations of Facial Expressions on PDE-Based Surfaces
NoParameterisation of facial expressions on PDE surface
representations of human faces are presented in this
work. Taking advantage of the boundary-value approach
inherent to Bloor-Wilson PDE method, facial expressions
are achieved by manipulating the original boundary curves.
Such curves are responsible for generating a surface representation
of a human face in its neutral configuration,
so that regions on these curves represent a given facial
expression in a fast and realistic manner. Additionally, the
parameterisation proposed here is carried out by applying
different mathematical transformations to the affected
curves according to the corresponding facial expression.
Full analytic expressions parameterising some of the most
common facial expressions such as smiling and eyebrow
raising are in this work. Some graphical examples of these
facial expressions are used to illustrate the results obtained
using Bloor-Wilson PDE method as the foundations of the
parameterisation scheme proposed here. Thus, it is shown
that an efficient, intuitive and realistic parameterisation of
facial expressions is attainable using Bloor-Wilson PDE
method in along with a suitable mathematical expression
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