RGB Filtering
Color (Intensity) Mode
Both RGB or Intensity can be saved as part of a point cloud. When this information is available, it can be used to colorize each individual cloud point while in the standard cloud display mode. This color in- formation will replace the standard cloud color and can be enable or disabled through the use of the Color (Intensity) Mode check box in the cloud properties menu. Only certain instruments and import formats (such as E57 or PTX) currently include RGB color or Intensity information.
Cloud Point display can also be edited based upon the cloud point color and intensity information. This is done by right-clicking on the cloud and selecting RBG Filtering. This will open a filter control dialog that will allow you to limit the displayed cloud points based upon a max and min thresholds that can be applied to Red, Green and Blue independently.
The check boxes next to the individual color components can be used to temporarily isolate the graphical display of the colors for the visible cloud points. This can be helpful for an instrument like the Leica ATS600 that saves the incidence (broadening) value in the Red color scheme while using Blue and Green to identify intensity. By unchecking the Blue and Green components the points will be displayed only using the red component making it easier to determine the ideal threshold to set in order to isolate the display of the desired cloud points.
Display of the select color or combination of colors will be updated when the Apply Filter buttons are pressed.
The individual controls function as follows:
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High/Low Threshold. These check boxes and numerical values define the filter threshold that will be applied to the cloud points. These values should be between 0 and 255.
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Incrementally Apply Filter. The selected settings are applied to the cloud as it is currently displayed without any consideration for hidden points.
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Reset and Apply Filter. The selected settings are applied to the entire cloud regardless of its current display status.
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Reset All Cloud Points Visible. This option will reset all the cloud points such that they are visible regardless of color.
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Save Filter As Default. This option applies the current filter settings as a Default filter available to all clouds.
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Delete Current Filter. Removed the current filter from the list of available filters.
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Clear All Filters. This option removed all the saved filters such that only the default filter will remain.
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Apply to selected. This button operates as a batch function al- lowing the selected settings in the current cloud to be applied to a selection of other point clouds.
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Save Filter. This option allows you to apply the current filter settings to the currently selected Filter. Remember that at any time new filters can be created by typing a name into the Filter Name field and saving the current settings.
A simple example of how to use this filter is as follows. Assume you have scanned a black and white target and you want to use this filter to identify the center point of the target:
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Right-click on the cloud in the graphics (or in the tree) and select RBG Filtering.
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Check the Grey Scale check box and the Low Threshold check box below it.
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Enter a mid range value (45 worked here) to separate the dark or lower return points and hide them by pressing the Reset and Apply Filter button. When you do the dark points will be hid- den. The threshold can be adjusted and the display of the cloud points edited as desired to extract clean lines on the target.
The Color Intensity Histogram was added to help in selecting the correct color values to use in the filtering process. It also has a Quality and Intensity mode which is more intuitive for new uses than editing the green or gray scale values depending on the instrument.
The Quality (Red) - Intensity (Green) Display Mode check box can be used to switch the controls for direct RGB selection to either Quality or Inten- sity only. The slider can then be used to position the cut off threshold logically based upon the frequency distribution of the data.
The contrast in the image can also be adjusted to the extents of the selected data range. This can be very helpful when trying to read text or identify visual cues from the intensity data. To do so, check the Re- set Grey Scale Contrast To Match Selected Range check box at the bottom of the histogram available in Grey Scale mode.
Using RGB Filtering with Leica ATS600 in SpatialAnalyzer -