From likkai@sirius.astro.uiuc.edu Wed Jun 5 05:37:13 1991 Received: from yoyodyne.ncsa.uiuc.edu by zaphod.ncsa.uiuc.edu (4.0/NCSA-1.2) id AA05012; Wed, 5 Jun 91 05:37:10 CDT Return-Path: Received: from ux1.cso.uiuc.edu by yoyodyne.ncsa.uiuc.edu (4.0/NCSA-1.2) id AA22350; Wed, 5 Jun 91 05:37:51 CDT Received: from sirius.astro.uiuc.edu by ux1.cso.uiuc.edu with SMTP id AA21305 (5.65c/IDA-1.4.4 for ); Wed, 5 Jun 1991 05:37:53 -0500 Received: from orion.astro.uiuc.edu.astro by sirius.astro.uiuc.edu (4.1/SMI-4.1) id AA27595; Wed, 5 Jun 91 05:35:53 CDT Date: Wed, 5 Jun 91 05:35:53 CDT From: likkai@sirius.astro.uiuc.edu (Jason NG) Message-Id: <9106051035.AA27595@sirius.astro.uiuc.edu> To: likkai@sirius.astro.uiuc.edu Subject: iso.doc Status: OR NCSA XDS releaase 2.0 Jason Ng 5-June-91 ISOSURFACE FEATURE ================== WHAT IT DOES The isosurface feature takes a 3D rectangular volume dataset and creates a surface within it with a value that you specify. Thus, it allows you to graphically "carve away" parts of your dataset, revealing a shape or surface that corresponds to points in the original dataset that have the same value [hence "iso (=same) surface"]. Several surfaces may be specified. The feature then generates a single image with all the different surfaces overlapping. ----------------------------------------------------------------------------- HOW TO INVOKE The isosurface feature applies only to 3D scientific datasets. It is invoked by clicking on the "IsoSurface Renderer" diamond button in the Data Attributes Window. This window pops up when you load a 3D dataset. You may specify the scale on the "Dicer/IsoSurf Scale" dialog on this window. It specifies how big the image will be. It is set to 3. ----------------------------------------------------------------------------- WHAT YOU MUST DO MINIMALLY Clicking on the "IsoSurface Renderer" diamond button (see above) pops up the Iso-surface action WIndow. You specify input parameters in this window, and the resulting image is displayed in this window. The rest of the document describes the sequence of steps that you must take from within the Iso-surface action window. (1) Specify how many surfaces to do. Enter the values in the "Surfaces" dialog, towards the bottom right. Don't specify too many. The default is 1. (2) Next, you must specify values for each surface you want. For each surface, you must specify the value, and the red,blue and green components. These are to be entered in the "Value", "Red", "Green" and "Blue" dialogs near to lower left. "Value" - the actual data value in your dataset to create a surface from. Usually a real number. "Red", "Green", "Blue" - all 3 must be specified and are combined by the program to determine the base color for that surface. Each is a value from 0.0 to 0.999. Thus to get a yellow surface, specify Red as 0.99, Green as 0.99 and Blue as 0.0. **THIS IS IMPORTANT: AFter setting the value and color, you must click on the "Set" button at the lower extreme left. You must do this for each surface you specify. The box above the "set" button tells you which surface you are currently setting values for. To edit values for the next surface, use the scroll bar to the right of the "Set' button. As it scrolls, values for the various surfaces are displayed. You can enter values for as many surfaces as you like, but don't forget specify the exact number of surfaces you want (see (1)). ****** This is the minimum that you need to enter. ******* At this point you may go ahead and click on the "View" button to start the process. The process can take some time. The cursor changes to a watch cursor, and when the process is done, the entire image is displayed at the end. ----------------------------------------------------------------------------- FANCY OPTIONS There are options for (a) rotating the dataset, to give a different view. (b) specifying a subcube to do the isosurface on instead. (c) generating several images in succession, to make an animation. (d) generating a "true color" shaded surface image. (e) generating a wire frame image instead of solid shading. All these are optional, are each may be specified independent of others. (a) Specify how much to rotate the dataset by entering (in DEGREES) values in the "Rot X", "Rot Y" and "Rot Z" dialogs. 30 degrees is a good value to try for each. Note that the "Rotate" square button (under the palette) should be ON. (as it is by default). Also the "Perspective" and "Attenuate" buttons should also be ON for the best effect. What this does it to create a perspective view, at an angle, with parts of the surfaces further away shown dimmer (attenauted lighting). (b) You can specify a subcube (or really, a sub rectangular chunk) to work on. This allows you to focus on some interesting part of your data. It can also speed up the process considerably. You define the subcube by specifying the start and end planes along the X, Y and Z axis: Enter the starting and ending points for the x-dimension in the dialogs "Start X" and "End X". These are integer values not exceeding the X dimension of your dataset. Also, endx must not be smaller than startx. Do the same for "Start Y" and "End Y" for the y-axis, and for "Start Z" and "End Z" for the z-axis. (c) You can generate several frames to form ian animation by varying the rotation angle manually. . You can automate the process by specifying how many frames you want done and the degree increments between frames along the x, y and z axis. Specify the number of frames in the "Frames" dialog. Enter a degree value in each of the "Inc X", "Inc Y" and "Inc Z" dialogs. To start generating the frames, click on the "Animate" button. This pops you a file window. You must specify a new file so that each frame can be saved into the file when it is generated. The frames are saved as raster images in a HDF file. As soon as you entered the file name and hit return, the process begins. When done, the entire sequence will have been saved in that file. This sequence can be viewed by invoking the Load 8-bit Raster option in XDataslice. (d) The "True Color" button should be ON for any of the red, green, and blue values that your entered per surface to make sense. Otherwise the surfaces are shaded with colors from the existing pallete. Specifying true color is useful when you have several surfaces, and you want each surface to be shaded with the distinct color that you specify. (e) To generate a wire frame image instead of solid shading, set the "Wire Frame" button ON. ----------------------------------------------------------------------------- MISCELLANEOUS (a) The "Update" button can be set to ON if you would like to watch the progress of the isosurface generation. As the surface is being generated, it will be displayed on the screen. (b) You may click on the "Clear" button to clear the previous image before generating a new one. Or you may choose to leave the previous there, and create another surface. This surface will be generated and merged into the previous image. It will determine which surface is overlapping which and redisplay the image accordingly. This produces very nice results. (c) The other dialogs "Focal Pt." and "Attenuate" are best left alone although experimenting can produce interesting results. (d) Finally, you can stop the process anytime with the "Stop" button. You can save any image as an HDF raster file with the "Save" button. (e) Status of progress during the isosurface generation is reported on the Main Window of XdataSlice. Have fun.