andyrose@batcomputer.tn.cornell.edu (Andy Rose) (12/08/90)
apE 2.0 manuals crossed my desk and they look good. There is one called The apE Tutorials 91 pp. and one called apE 2.0 User/Reference Manual. 155 pp. From table of contents Tutorials: Tutorial #1 - Learning to use Wrench (the interactive network construction tool) 4.1 Intro to Wrench 4.2 Creating a Pipeline 4.3 Loading and Editing Pipelines 4.4 Where to go from here #2 Visualizing 2D Data 5.1 Getting started with 2D Computational Fluid Simulations 5.2 Getting Started with Jet Exhaust 5.3 Colliding Stars #3 Viewing 3D Data 6.1 Getting started with 3D scenes 6.2 Creating the Pipeline 6.3 Invoking the Pipeline 6.4 Panorama - The Scene Editor 6.5 Property - The Property Group Editor 6.6 Where to go from here #4 Rendering 3D Volumes 7.1 Getting Started with Volume Rendering 7.2 Creating the pipeline 7.3 Invoking the pipeline 7.4 Changing the parameters An example of a Reference Manual entry " Name opac - volume render a three-dimensional variable Synopsis opac [std_flags] [-b] [-f] Description [nice picture of a ghostly looking thing inside a cube] opac is a volume renderer based on the article: Levoy, Marc, "Display of Surfaces from Volume Data", IEEE Computer Graphics and Apps.,May 88, Vol. 8, No. 3, pp 29-37 Flux Input variable A 3D scalar variable with a grid as its spatial reference. Opacities are calculated using this variable. color_variable (optional) A 3D variable of 4 component color vectors, such as the output of 'mapcolor' or 'maprgb'. Its spatial reference must be identical to the input variable's spatial reference. Color is determined using this variable. object (optional) An object with a grid as its geometry may be sent to opac. Opac will use this grid as the spatial reference for the variables. The object may be interactively positioned in 'panorama' before it is sent to opac for viewing. view The view defines the eye point from which the volume will be viewed. scene The scene contains information that affects the way the volume is shaded. property The property contains information about the visual characteristics of the volume. light The light group determines the lighting for the scene. More than one light group may be sent to opac. Output: image The final image Interactive Controls: interval (float dial) The sampling interval along the rays. The default is 1.0. threshold (float dial) The data value at which the opacity will be maximum. The default is 0.0 opacity (float dial) The maximum opacity. A value of 0.0 is fully transparent, 1.0 is opaque. Default 0.5. r (float dial) A scale factor used in determining how close a voxel's data value must be to the selected threshold for it to be visible. Default 1.0. Operation [description from Levoy's paper of the technique] Options -b Reverse the gradients so that they point towards data values lower than the threshold -f The gradients will point toward data values higher than the threshold. This is the default. Once an opacity and color is assigned to every voxel, rays are cast from each pixel of the image through the volume to create the final image. The view group determines the direction of the ray. The view is a perspective view, unlike the view described in Levoy's paper, so the rays are not all cast in the same direction. The volume is sampled at even intervals along the ray. The sample interval can be changed using the 'interval' control. For all voxels along the ray to be sampled, the interval should be less than the shortest edge of a voxel. At each sample point that falls within the volume, a color and opacity is trilinearly interpolated from the eight voxels surrounding the sample point. The opacities and colors are summed along the ray, beginning at the sample that is closest to the eye. When the opacity reaches fully opaque, the sampling stops and the pixel is assigned the color at that point. If full opacity is not reached, afully opaque background color is added to the color to determine the final color for the pixel. Examples Related Information grad mapcolor maprgb objgrid pur Limitations Only variables with regular, rectangular grids as their spatial reference can be rendered. Opac currently only searches for one threshold. It is not possible to shade the volume using both front-facing and back-facing gradients as 'onion' is capable of doing. This means that in areas of the volume where the gradient is opposite the direction selected with the flags, the visible zones will be black, even if a light shines directly on them. To lighten up the images,the ambient light in the input property must be increased. Opac currently only shows perspective views. " These documents evidence care and concern. It would be nice to build some kind of apE applications which could be used to benchmark the various hardware. (apEstones) The manual lists the following hardware support: Cray X-MP, Y-MP (UNICOS) Convex C-1, C-2 Sun Silicon Graphics NeXT Hewlett-Packard DEC (ULTRIX) Stardent IBM RS6000 (AIX) Apple Mac II (A/UX) from p. 10 Reference Manual How do you get apE? apE is being distributed for a nominal $75.00 fee. More information is available via anonymous ftp from apE.osgp.osc.edu at 128.146.18.18 or by e-mail to apE@apE.osgp.osc.edu To obtain ordering and license forms, please call 614 292 0006 The Ohio Supercomputer Center 1224 Kinnear Road Columbus, OH 43212 FAX 614 292 7168 V for vis. -- Andrew Newkirk Rose '91 Department of Visualization CNSF/Theory Center 632 E & T Building, Hoy Road Ithaca, NY 14583 607 254 8686 andy@cornellf.tn.cornell.edu