Imaging vector fields has applications in science, art, image processing and special effects. An effective new approach is to use linear and curvilinear filtering techniques to locally blur textures along a vector field. This approach builds on several previous texture generation and filtering techniques[8, 9, 11, 14, 15, 17, 23]. It is, however, unique because it is local, one-dimensional and independent of any predefined geometry or texture. The technique is general and capable of imaging arbitrary two- and three-dimensional vector fields. The local one-dimensional nature of the algorithm lends itself to highly parallel and efficient implementations. Furthermore, the curvilinear filter is capable of rendering detail on very intricate vector fields. Combining this technique with other rendering and image processing techniques — like periodic motion filtering — results in richly informative and striking images. The technique can also produce novel special effects.

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Imaging vector fields using line integral convolution

We present a method to acquire the reflectance field of a human face and use these measurements to render the face under arbitrary changes in lighting and viewpoint. We first acquire images of the face from a small set of viewpoints under a dense sampling of incident illumination directions using a light stage. We then construct a reflectance function image for each observed image pixel from its values over the space of illumination directions. From the reflectance functions, we can directly generate images of the face from the original viewpoints in any form of sampled or computed illumination. To change the viewpoint, we use a model of skin reflectance to estimate the appearance of the reflectance functions for novel viewpoints. We demonstrate the technique with synthetic renderings of a person's face under novel illumination and viewpoints.

/pdf/acquiring-the-reflectance-field-of-a-human-face-1q7nifn0px.pdf

Acquiring the reflectance field of a human face

The present invention was developed by a neurosurgeon and seeks to mimic the results of primate neurological research which is indicative of a human's actual neurological control structures and logic. Specifically, the motor proprioceptive and tactile neurophysiology functioning of the surgeon's hands and internal hand control system from the muscular level through the intrafusal fiber system of the neural network is considered in creating the robot and method of operation of the present invention. Therefore, the surgery is not slowed down as in the art, because the surgeon is in conscious and subconscious natural agreement and harmonization with the robotically actuated surgical instruments based on neurological mimicking of the surgeon's behavior with the functioning of the robot. Therefore, the robot can enhance the surgeon's humanly limited senses while not introducing disruptive variables to the surgeon's naturally occurring operation of his neurophysiology. This is therefore also a new field, neurophysiological symbiotic robotics.

Surgical robot and robotic controller

We describe a novel method for surgery simulation including a volumetric model built from medical images and an elastic modeling of the deformations. The physical model is based on elasticity theory which suitably links the shape of deformable bodies and the forces associated with the deformation. A real time computation of the deformation is possible thanks to a preprocessing of elementary deformations derived from a finite element method. This method has been implemented in a system including a force feedback device and a collision detection algorithm. The simulator works in real time with a high resolution liver model.

https://hal.inria.fr/inria-00073173/document

Real-time elastic deformations of soft tissues for surgery simulation

Improved robotic surgical systems, devices, and methods often include a first assembly with a surgical end effector supported and manipulated relative to a first base by a first robotic linkage, while a second surgical end effector manipulated and supported relative to a second, independent base by a second robotic linkage. One or more of these robotic assemblies may be moved relative to the other. To coordinate the end effector movements with those of input devices being manipulated by a surgeon relative to a display of a surgical worksite, the processor deriving the commands for movement of the robotic linkages may make use of a signal indicating a relative orientation of the bases of the robotic arm assemblies. Surprisingly, the robotic arm assemblies may not transmit signals to the processor indicating a relative translational position of the bases.

Arm cart for telerobotic surgical system

We have developed a prototype teleoperated microsurgical robot MSR-1 and associated virtual environment for eye surgery. Bidirectional pathways relay visual, auditory, and mechanical information between the MSR-1 master and slave. The surgeon wears a helmet visual master that is used to control the orientation of a stereo camera system visual slave observing the surgery. Images from the stereo camera system are relayed back to the helmet or adjacent screen where they are viewed by the surgeon. In each hand the surgeon holds a pseudotool a shaft shaped like a microsurgical scalpel that projects from the left and right limbs of a force reflecting interface mechanical master. Movements of the left and right pseudotools cause corresponding movements scaled down by 1 to 100 times in the microsurgical tools held by the left and right limbs of the micromotion robot mechanical slave that performs the surgery. Forces exerted on the left and right limbs of the slave microsurgical robot via the microtools are reflected back after being scaled up by 1 to 100 times to the pseudotools and hence surgeon via actuators in the left and right limbs of the mechanical master. This system enables tissue cutting forces to be felt including those that would normally be imperceptible if they were transmitted directly to the surgeon's hands. The master and slave subsystems visual, auditory, and mechanical communicate through a computer system which serves to enhance and augment images, filter hand tremor, perform coordinate transformations, and perform safety checks. The computer system consists of master and slave computers that communicate via an optical fiber connection. As a result, the MSR-1 master and slave may be located at different sites, which permits remote robotic microsurgery to become a reality. MSR-1 is being used as an experimental testbed for studying the effects of feedforward and feedback delays on remote surgery and is used in research on enhancing the accuracy and dexterity of microsurgeons by creating mechanical and visual telepresence.

A teleoperated microsurgical robot and associated virtual environment for eye surgery

An anatomically detailed 3-D computer graphic model of the eye and surrounding face within a virtual environment has been implemented for use in a surgical simulator. The simulator forms part of a teleoperated micro-surgical robotic system being developed for eye surgery. The model has been designed to both visually and mechanically simulate features of the human eye by coupling computer graphic realism with finite element analysis.The paper gives an overview of the system with emphasis on the graphical modelling techniques and a computationally efficient framework for representing anatomical details of the eye and for finite element analysis of the mechanical properties. Examples of realistic images coupled to large deformation finite element model of the cornea are presented. These images can be rendered sufficiently fast for the virtual reality application.

A virtual environment and model of the eye for surgical simulation

Blind Mexican cave fish (Astyanax fasciatus) sense the presence of nearby objects by sensing changes in the water flow around their body. The information available to the fish using this hydrodynamic imaging ability depends on the properties of the flow field it generates while gliding and how this flow field is altered by the presence of objects. Here, we used particle image velocimetry to measure the flow fields around gliding blind cave fish as they moved through open water and when heading towards a wall. These measurements, combined with computational fluid dynamics models, were used to estimate the stimulus to the lateral line system of the fish. Our results showed that there was a high-pressure region around the nose of the fish, low-pressure regions corresponding to accelerated flow around the widest part of the body and a thick laminar boundary layer down the body. When approaching a wall head-on, the changes in the stimulus to the lateral line were confined to approximately the first 20% of the body. Assuming that the fish are sensitive to a certain relative change in lateral line stimuli, it was found that swimming at higher Reynolds numbers slightly decreased the distance at which the fish could detect a wall when approaching head-on, which is the opposite to what has previously been expected. However, when the effects of environmental noise are considered, swimming at higher speed may improve the signal to noise ratio of the stimulus to the lateral line.

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The flow fields involved in hydrodynamic imaging by blind Mexican cave fish (Astyanax fasciatus). Part I: open water and heading towards a wall.

Blind Mexican cave fish (Astyanax fasciatus) are able to sense detailed information about objects by gliding alongside them and sensing changes in the flow field around their body using their lateral line sensory system. Hence the fish are able to build hydrodynamic images of their surroundings. This study measured the flow fields around blind cave fish using particle image velocimetry (PIV) as they swam parallel to a wall. Computational fluid dynamics models were also used to calculate the flow fields and the stimuli to the lateral line sensory system. Our results showed that characteristic changes in the form of the flow field occurred when the fish were within approximately 0.20 body lengths (BL) of a wall. The magnitude of these changes increased steadily as the distance between the fish and the wall was reduced. When the fish were within 0.02 BL of the wall there was a change in the form of the flow field owing to the merging of the boundary layers on the body of the fish and the wall. The stimuli to the lateral line appears to be sufficient for fish to detect walls when they are 0.10 BL away (the mean distance at which they normally swim from a wall), but insufficient for the fish to detect a wall when 0.25 BL away. This suggests that the nature of the flow fields surrounding the fish are such that hydrodynamic imaging can only be used by fish to detect surfaces at short range.

/pdf/the-flow-fields-involved-in-hydrodynamic-imaging-by-blind-67ilbxv7na.pdf

The flow fields involved in hydrodynamic imaging by blind Mexican cave fish (Astyanax fasciatus). Part II: gliding parallel to a wall.

A new methodology has been developed for constructing streamlines and particle paths in numerically generated fluid velocity fields. A graphical technique is used to convert the discretely defined flow within a cell into one represented by two three-dimensional stream functions. Streamlines are calculated by tracking constant values of each stream function, a process which corresponds to finding the intersection of two stream surfaces. The tracking process is mass conservative and does not use a time stepping method for integration, thus eliminating a computationally intensive part of traditional tracking algorithms. The method can be applied generally to any three-dimensional compressible or incompressible steady flow. Results presented here compare the performance of the new method to the most commonly used scheme and show that calculation times can be reduced by an order of magnitude.

Gordon D. Mallinson

Papers

A teleoperated microsurgical robot and associated virtual environment for eye surgery

A virtual environment and model of the eye for surgical simulation

The flow fields involved in hydrodynamic imaging by blind Mexican cave fish (Astyanax fasciatus). Part I: open water and heading towards a wall.

The flow fields involved in hydrodynamic imaging by blind Mexican cave fish (Astyanax fasciatus). Part II: gliding parallel to a wall.

A 3-D streamline tracking algorithm using dual stream functions