Direct Volume Rendering
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Scientific visualization of volume data is increasingly being used in applications such as Medical Imaging and Computational Fluid Dynamics (CFD). Due to the irregular nature of the geometry of (CFD) applications, volume data for (CFD) applications is stored in curvilinear or unstructured grids. This increases the computational and memory resources needed to render the volume due to the limited amount of geometrical coherence that can be exploited. A method of rendering multiple, possibly intersecting, curvilinear and unstructured grids is presented. This method, which has been implemented for a MIMD parallel architecture is based on a scan-line algorithm and provides ray-traced quality images efficiently by taking advantage of polygonal coherence between scan-lines. It is capable of rendering intersecting grids without the computational and spatial expense of subdividing intersecting cells, which most ray-tracing and all cell projection methods must do. Further efficiency is obtained by the use of a K-dimensional tree with prefix-order partitioning of triangles, to reduce the number of primitives that must be processed for one rendering. All rendering is done in software which eliminates the need for specialized graphics hardware. (Movie is 1.5 Meg) |
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This paper describes a technique to accurately simulate
a balloon expanding and bursting.
Physical simulation is achieved through use of a spring-damper model with
point masses to represent the surface of the balloon.
Visual characteristics of the balloon, such as variable opacity and variable
shininess are also addressed by this approach using material attributes
in the SGI lighting model.
Spring constants are user-definable as a function of height and
internal pressure of the balloon is also controlled by the user.
Bursting is achieved by using spring thresholds which allow for fractures
in the surface and lead to a chain reaction of spring failures.
Balloon models can be created in a 3D sculpting program by an isosurface
algorithm and can be used by the simulation. By using physically based modeling techniques, the problem can be simplified and easily implemented using a few simple data structures. To maintain simplicity and minimize elapsed time between frames, collision detection will not be implemented in this model. By using SGI graphics hardware to render the balloon, interactive rates can be achieved for simple balloon models, however, more complex balloons will result in longer delays between frames. (Movie is 1.2 Meg) |
There are many techniques to obtaining a convoluted surface from a set of control data points. This project focuses on using gaussian filters on a set of points represented by an octree data structure to give a smooth surface. The surface will the be drawn as a set of polygons as determined by a modified implicit surface routine based on the marching cubes algorithm. The octree data structure, which holds the 3D information, is generated by a previous work which gives the user a sculpting environment to work in. |
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