Modifying 3-D surfaces
Click the Modify 3D-Surface button. You will find the button in the lower left cor- ner of the 3D window by default. Some options contained in this dialog box are described in the following.
Height You can set the relative height of the model surface as you like. Height is cor- rectly scaled for calibrated height maps. Models created using non-calibrated height maps will have height values determined in proportion to image intensity.
Resolution The level of detail and how smooth the model surface is depend on how many height-map pixels are used to compute the model. This is what step width de- fines.
[Ctrl] + arrow keys rotation/tilt to the right (or left, backwards, forwards) [Shift] + arrow keys move rightward (or leftward, upwards, downwards)
[Shift] + [PageUp] ([PageDown])
reduce in size (or enlarge) [Shift] + [Home] reset to default position
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Restricting image area for model
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You can cut out the desired image structure using a frame in the height map (Modify 3D-Surface > ROI): this is how you create a model based on an image segment.
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Globally-set frames (Image > Set Frame) are of no use here.•
Height maps based on stereographs, for example, have a border whose gray value is constant. Click the Modify 3D-Surface > Auto-ROI button to have this border clipped automatically.•
If you wish to compute a model based on one or multiple arbitrarily-shaped image segments, you need to define a mask image. While pressing [Ctrl], drag the mask image onto the 3D window. Activate/deactivate the mask via the Modify 3D-Surface > Use mask check box.Step-by-step
Setting height
1) Make the grid visible to be able to see the scale graduation of the axes. This is done by clicking on the Hide Bottom Grid button (3-D button bar) so that it is not depressed.
2) Click the Modify 3D-Surface... button (Surface button bar at the lower edge of the 3D window).
3) Enter the percental height of the brightest or highest pixel of the height map relative to the maximum value of length and width into the Height field.
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An entry of 0% results in a model that is a plane. At 100%, the model’s height equals its length/width. Low percentages yield flatter, gently-in- clined models; higher percentages more steeply-inclined models.4) Select the Display data check box to have length, width and height shown.
5) Close the Modify 3D-Surface dialog box. When working with a cali-
brated height image you can determine the height of the model surface via the data visualized - length, width and height (above left). If the height image is uncalibrated you simply have to judge us- ing your own eyes.
Setting resolution
1) Click the Modify 3D-Surface... button (Surface button bar at the lower edge of the 3D window).
2) The entry you make into the Step width field determines whether, e. g., ev- ery 10th pixel of the height map is to be used for the display of the model (if you enter "10").
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The default entry is "10". In many cases this is, in fact, a suitable com- promise.3) Increase the step width if the model has too many peaks obscuring the model’s primary structure, thus interfering with the overall (visual) impres-
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sion the model makes.
Apply a smoothing filter (e. g., Oper > Filter > NxN) to the height map be- fore creating the model to reduce high contrast transitions and to avoid sharp edges.
4) Decrease the step width if the model appears unnaturally rough or if signif- icant surface detail is not apparent.
The lower the step width, the slower the motion of the model because more points have to be computed for display of the model.
5) Select the Display as grid check box.
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The continuous model surface will disappear from view and be re- placed by a grid representing the surface structure. The height of the grid nodes are computed via the corresponding intensity values of the height map. Any interjacent height values of the model will be com- puted by interpolation.6) Observe how the mesh size of the grid increases and decreases parallel to your increasing and decreasing step width.
7) Now clear the Display as grid check box.
8) Close the Modify 3D-Surface dialog box. Step width determines how
detailed and how smooth the surface of the model is displayed. Too much image information may interfere with display of the model surface (above: step width of 5; below: step width of 20).
Creating a model of an image segment
1) Click the Modify 3D-Surface... button (Surface button bar at the lower edge of the 3D window).
2) Click the ROI... button to create a model based on a rectangular segment of the height map.
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The image window containing the height map will be activated. Define the image segment desired using the red frame.•
This is how you can cut out a particular surface structure, or clip dark or light image edges.Creating 3-D surfaces Coloring models - Background information
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Use ROIs or masks to dis- play the desired segment of the height map as a model.