33 research outputs found
Scalable Real-Time Vehicle Deformation for Interactive Environments
This paper proposes a real-time physically-based method for simulating
vehicle deformation. Our system synthesizes vehicle deformation characteristics
by considering a low-dimensional coupled vehicle body technique. We simulate
the motion and crumbling behavior of vehicles smashing into rigid objects. We
explain and demonstrate the combination of a reduced complexity non-linear
finite element system that is scalable and computationally efficient. We use an
explicit position-based integration scheme to improve simulation speeds, while
remaining stable and preserving modeling accuracy. We show our approach using a
variety of vehicle deformation test cases which were simulated in real-time
Dual-Quaternion Julia Fractals
Fractals offer the ability to generate fascinating geometric shapes with all
sorts of unique characteristics (for instance, fractal geometry provides a
basis for modelling infinite detail found in nature). While fractals are
non-euclidean mathematical objects which possess an assortment of properties
(e.g., attractivity and symmetry), they are also able to be scaled down,
rotated, skewed and replicated in embedded contexts. Hence, many different
types of fractals have come into limelight since their origin discovery. One
particularly popular method for generating fractal geometry is using Julia
sets. Julia sets provide a straightforward and innovative method for generating
fractal geometry using an iterative computational modelling algorithm. In this
paper, we present a method that combines Julia sets with dual-quaternion
algebra. Dual-quaternions are an alluring principal with a whole range
interesting mathematical possibilities. Extending fractal Julia sets to
encompass dual-quaternions algebra provides us with a novel visualize solution.
We explain the method of fractals using the dual-quaternions in combination
with Julia sets. Our prototype implementation demonstrate an efficient methods
for rendering fractal geometry using dual-quaternion Julia sets based upon an
uncomplicated ray tracing algorithm. We show a number of different experimental
isosurface examples to demonstrate the viability of our approach
Convex Hulls: Surface Mapping onto a Sphere
Writing an uncomplicated, robust, and scalable three-dimensional convex hull
algorithm is challenging and problematic. This includes, coplanar and collinear
issues, numerical accuracy, performance, and complexity trade-offs. While there
are a number of methods available for finding the convex hull based on
geometric calculations, such as, the distance between points, but do not
address the technical challenges when implementing a usable solution (e.g.,
numerical issues and degenerate cloud points). We explain some common algorithm
pitfalls and engineering modifications to overcome and solve these limitations.
We present a novel iterative method using support mapping and surface
projection to create an uncomplicated and robust 2d and 3d convex hull
algorithm
Real-Time Character Rise Motions
This paper presents an uncomplicated dynamic controller for generating
physically-plausible three-dimensional full-body biped character rise motions
on-the-fly at run-time. Our low-dimensional controller uses fundamental
reference information (e.g., center-of-mass, hands, and feet locations) to
produce balanced biped get-up poses by means of a real-time physically-based
simulation. The key idea is to use a simple approximate model (i.e., similar to
the inverted-pendulum stepping model) to create continuous reference
trajectories that can be seamlessly tracked by an articulated biped character
to create balanced rise-motions. Our approach does not use any key-framed data
or any computationally expensive processing (e.g., offline-optimization or
search algorithms). We demonstrate the effectiveness and ease of our technique
through example (i.e., a biped character picking itself up from different
laying positions)
Inverse Kinematics with Dual-Quaternions, Exponential-Maps, and Joint Limits
We present a novel approach for solving articulated inverse kinematic
problems (e.g., character structures) by means of an iterative dual-quaternion
and exponentialmapping approach. As dual-quaternions are a break from the norm
and offer a straightforward and computationally efficient technique for
representing kinematic transforms (i.e., position and translation).
Dual-quaternions are capable of represent both translation and rotation in a
unified state space variable with its own set of algebraic equations for
concatenation and manipulation. Hence, an articulated structure can be
represented by a set of dual-quaternion transforms, which we can manipulate
using inverse kinematics (IK) to accomplish specific goals (e.g., moving
end-effectors towards targets). We use the projected Gauss-Seidel iterative
method to solve the IK problem with joint limits. Our approach is flexible and
robust enough for use in interactive applications, such as games. We use
numerical examples to demonstrate our approach, which performed successfully in
all our test cases and produced pleasing visual results.Comment: arXiv admin note: substantial text overlap with arXiv:2211.0033
BHPR research: qualitative1. Complex reasoning determines patients' perception of outcome following foot surgery in rheumatoid arhtritis
Background: Foot surgery is common in patients with RA but research into surgical outcomes is limited and conceptually flawed as current outcome measures lack face validity: to date no one has asked patients what is important to them. This study aimed to determine which factors are important to patients when evaluating the success of foot surgery in RA Methods: Semi structured interviews of RA patients who had undergone foot surgery were conducted and transcribed verbatim. Thematic analysis of interviews was conducted to explore issues that were important to patients. Results: 11 RA patients (9 ♂, mean age 59, dis dur = 22yrs, mean of 3 yrs post op) with mixed experiences of foot surgery were interviewed. Patients interpreted outcome in respect to a multitude of factors, frequently positive change in one aspect contrasted with negative opinions about another. Overall, four major themes emerged. Function: Functional ability & participation in valued activities were very important to patients. Walking ability was a key concern but patients interpreted levels of activity in light of other aspects of their disease, reflecting on change in functional ability more than overall level. Positive feelings of improved mobility were often moderated by negative self perception ("I mean, I still walk like a waddling duck”). Appearance: Appearance was important to almost all patients but perhaps the most complex theme of all. Physical appearance, foot shape, and footwear were closely interlinked, yet patients saw these as distinct separate concepts. Patients need to legitimize these feelings was clear and they frequently entered into a defensive repertoire ("it's not cosmetic surgery; it's something that's more important than that, you know?”). Clinician opinion: Surgeons' post operative evaluation of the procedure was very influential. The impact of this appraisal continued to affect patients' lasting impression irrespective of how the outcome compared to their initial goals ("when he'd done it ... he said that hasn't worked as good as he'd wanted to ... but the pain has gone”). Pain: Whilst pain was important to almost all patients, it appeared to be less important than the other themes. Pain was predominately raised when it influenced other themes, such as function; many still felt the need to legitimize their foot pain in order for health professionals to take it seriously ("in the end I went to my GP because it had happened a few times and I went to an orthopaedic surgeon who was quite dismissive of it, it was like what are you complaining about”). Conclusions: Patients interpret the outcome of foot surgery using a multitude of interrelated factors, particularly functional ability, appearance and surgeons' appraisal of the procedure. While pain was often noted, this appeared less important than other factors in the overall outcome of the surgery. Future research into foot surgery should incorporate the complexity of how patients determine their outcome Disclosure statement: All authors have declared no conflicts of interes