Scanning¶

Base Removal: Erasing a Supporting Surface¶

When you capture an object, you can often omit from the scan any surface that supports the object. The Base removal option serves this purpose. To employ this option, first indicate the surface on which the object is resting and then capture the object. If this approach is unsuitable for your situation, clear the Enable automatic base removal checkbox.

1. Open the Scan panel.

2. Make sure the Enable automatic base removal checkbox is selected.

3. Click Preview and direct your scanner at the surface that supports object (e.g., a table or the floor). A gray wireframe plane will appear, indicating the scene’s base.

4. Once the application detects the base, it will display a message: “Now scan the object.”

   Important

   If Artec Studio fails to detect a supporting surface, you can still start recording.

5. Direct the scanner at the object and click Record ()

6. Scan the object freely. You can pause and resume the session as necessary.

7. Click Stop; all scans will move to the coordinate system with the Z axis normal to the base.

8. Close the Scan panel. After Artec Studio performs Fine registration, the Base removal algorithm will remove the previously detected supporting surface.

Figure 41. Scanning with the Enable automatic base removal option.

Resuming Scan After Lost Tracking¶

Artec Studio records adjacent frames on the basis of common surface features. If the scanner stops recognizing common features, it will stop capturing the scene. This situation is called lost tracking; if it happens, just direct the scanner at a recently captured region. There are, however, nuances, which we address below.

Table 2. lists several causes of lost tracking. The most common is moving the scanner too fast.

Figure 42. Alert message: tracking lost.

The Scan using auto-alignment option may ease the process of resuming tracking (this option is enabled by default in the application settings). Note the following:

• Artec Studio switches almost instantly from displaying Tracking lost mode (see Figure 42.) to Searching for position, which appears on a green background.

• To continue scanning, direct the scanner at a region you’ve already captured.

  • Try to maintain the original scanner orientation toward this region
  • You need not necessarily use the most recent one, but it should have sufficient texture features.

• If the application successfully resumes tracking, it will start recording in a newly created scan. This new scan will already be aligned with the previous one.

The Scan Using Auto-Alignment section describes system behavior when this option is disabled.

Continue Scanning From Scans Selected in Workspace¶

Auto-alignment is a great timesaver and may help simplify further processing. But for projects that involve scans using Geometry + Texture tracking and for which the actual scene is unchanged, you can continue scanning immediately:

1. Ensure that the Scan using auto-alignment option is turned on in Settings (see Capture).
2. Mark previously captured scans using the icon in the Workspace panel.
3. Select Geometry + Texture tracking as well as the Continue scanning from scans selected in workspace checkbox in the Scan panel.
4. Click Preview, direct the scanner at a textured region you’ve already captured textured region—maintaining the original scanner orientation—and then click Record.
5. If tracking resumes successfully, Artec Studio will align the newly recorded scan with the selected ones.

Scanning With Real-Time Fusion¶

Real-time fusion is a special mode in which Artec Studio builds a 3D model in real time while you’re scanning. It’s the easiest and fastest way to obtain a model, but it cannot completely replace the normal workflow for processing raw scans after capturing them. Thus, we recommend avoiding Real-time fusion in the following cases:

• The scene is large and the amount of GPU memory is limited
• Objects have complicated shapes that cannot be captured in one scan session
• The object has small geometric details
• Extra-high accuracy is required

The Real-time fusion feature is available for each tracking method.

1. Open the Scan panel.
2. Select the required tracking mode.
3. Select the Real-time fusion checkbox [2].
4. Click Preview and then Record. Observe the recommendations in Scanning Procedure.
5. Pause and resume the session as necessary.
6. When you stop scanning, the Workspace panel will add one or more raw scans named Scan1, Scan2, Scan3 and so on, as well as one model named Scan1-Fusion. The number of these raw scans corresponds to how many times you pause and resume scanning (see Figure 43.).

Figure 43. Workspace panel after using Real-time fusion.

You can access the Settings window and use the Performance tab to configure the following Real-time fusion settings (see Real-Time Fusion Settings):

Voxel size

3D resolution of the model (i.e., the size of the triangulation-grid step in millimeters). The smaller the value, the more geometric details you can detect and capture in 3D.

Target-Assisted Scanning¶

Generally, you don’t need any special equipment to record using an Artec scanner. If the object has hard-to-scan regions, however, targets may be useful. In some cases, they can improve tracking and further registration.

Placing Targets¶

Whatever the method chosen, you should place at least non-coded targets on the object.

Attach non-coded targets (Figure 44.) to the object using the following rules:

• Try to place them on flat elements
• Avoid uneven surfaces
• Avoid obstructing significant geometric elements

Figure 44. Non-coded targets placed on an object.

Note

You can specify the target size in the Settings dialog of Artec Studio, as Photogrammetry Settings describes. If you use non-coded targets from the Scan Reference kit, specify 5 mm for the inner diameter and 10 mm for the outer diameter. You should measure targets from other suppliers and specify both diameters in the appropriate fields of the Settings dialog.

Place coded targets if your choice is photogrammetry (Using Photogrammetry Solution (Scan Reference)).

1. Prepare the objects and surrounding scene. All objects must remain stationary during measurement and capture.
2. Place the cross (Figure 46.) on the scene, ensuring that it rests firmly, and it is seen from most points of view. Also double check that all targets on the cross are clearly visible.
3. Place the coded targets on the object and the surroundings. Note that you should distribute them such that at least six to eight coded targets are visible in each image. Random placement is preferable; avoid symmetry and target alignment.

Figure 45. Coded targets.

Using Photogrammetry Solution (Scan Reference)¶

By using a combination of special reference targets and photogrammetric measurements, you can scan large areas in one session, improve the accuracy of captured surfaces and boost productivity by reducing postprocessing time. The only downside of this method is the preparation. After scanning, however, you need not align the scanned surfaces, so you can immediately proceed to Fusion (see the order of postprocessing steps in 3D Scanning at a Glance).

This synergy of technologies is possible thanks to Artec 3D-scanner and photogrammetry solutions. Several third-party photogrammetry offerings are available on the market. Scan Reference photogrammetry is one example. The Scan Reference kit includes hardware and software (see Figure 46.), a digital camera, a reference-scale cross, non-coded sticky targets (which Artec Studio uses to match the captured 3D data to the photogrammetric measurements), and reusable magnetic coded targets (required to automatically carry out measurements in the Scan Reference software).

Figure 46. Scan Reference kit

The kit includes (from left to right) coded targets (foreground), a digital camera, a scale cross, a roll of tape with non-coded targets and a carry case.

To perform scanning using targets, follow these steps:

1. Take several photos of the object from different angles. To determine the appropriate number of photos, angles and targets for each image, as well as required settings for a calibrated digital camera, consult the Scan Reference user manual and FAQ article. General recommendations are as follows:

1. Take photographs at a distance of 0.5–1.5 meters with enabled flash
2. Each photograph should contain as much targets as possible and each target should be captured at least in 10 photos
3. Entire cross should be captured in first 10–12 photographs
4. Capture the object from all sides

1. Move the cross and the coded targets away from the scene.
2. Connect the camera to a PC, then transfer and process the photos using the Scan Reference software. Once the calculations are complete, the software will display measurement results on the screen. These results can appear as a point table or a 3D model.
3. Save the point model in an *.obc file. This format is the software’s default.
4. Open the Scan panel in Artec Studio. Select Targets under Features to track.
5. Click Load targets from file and specify the OBC file path.
6. Scan the object. When you finish, the software will align all scans.

Important

If you don’t want the texture and geometry features to assist target scanning, select the Disable hybrid tracking for .obc checkbox (Photogrammetry Settings).

Notes on Scanning With Spider¶

Because Artec Spider has smaller field of view and provides higher accuracy in comparison with Artec EVA, scanning using it can pose difficulties. Consider the recommendations given in Technique and also the following:

• Opt for rotating table if possible
• Use a piece of paper with text on it as artificial texture
• Double check that objects don’t change their shape and position
• Try tuning sensitivity in particular cases (see Sensitivity). Avoid extreme values.

We recommend using the Artec Spider scanner only after it reaches its normal operating temperature. As soon as you plug Artec Spider in or connect it to a PC, it starts warming up. If you open the Scan panel, you will see two lines that provide the device’s current and optimal temperatures. Artec Spider will warm up faster when it’s in Preview mode. The Scan panel also displays additional information about the time remaining until the scanner reaches its optimal temperature.

Notes on Scanning With Third-Party 3D Sensors¶

Third-party 3D sensors (see Third-Party 3D Sensors) are not specifically designed to serve as 3D scanners. Because they are multipurpose devices made from inexpensive components, they can scan objects, but the texture and surface quality is far worse than that of professional Artec 3D scanners (see Figure 47.). The operating ranges and fields of view for all Artec Studio Ultimate–supported third-party sensors are shown in Figure 172..

When using third-party 3D sensors, bear in mind the following:

Providing good lighting is critical

because none of the sensors offers built-in flash. Also, use of these devices precludes the ability to adjust the brightness of the texture you are scanning, so good lighting is crucial to obtaining a decent model. Avoid using too much illumination, and avoid using direct light or fluorescent lamps. Intel RealSense R200 is particularly sensitive to direct sunlight.

When using PrimeSense and Asus Xtion sensors,

a special technique can help you capture surfaces with consistent brightness:

1. Click the Preview button
2. Direct the sensor at the object and hold it for 5 seconds while the sensor adjusts white balance and exposure
3. Click the Record button
4. Move the scanner slowly to capture the scene
5. While scanning, keep the sensor as close to the object as possible

Most third-party devices work in the Real-time fusion mode,

except for Kinect v2. Moreover, this mode is default for Intel RealSense 3D sensors.

Figure 47. Object captured and processed

(Artec EVA scan on left and PrimeSense on right).

Notes on Scanning With MHT¶

The flash feature in an Artec MHT scanner has a very large but limited number of operation cycles, so ensure that you disable the scanner when it’s not in use. Avoid leaving the Artec MHT on for a long time when using the maximum capture rate (15 frames per second). Artec Studio will automatically turn off the Artec MHT after five minutes of continuous operation. Normally the active mode/rest mode is 3 minutes of scanning and 7 minutes of rest; this mode is optimal and significantly increases the lifetime of the flash.

Tuning Texture Brightness¶

You can adjust the Texture brightness setting in Preview mode. Use the slider to increase or decrease the brightness of frames captured by the color camera (see Figure 49.). Note that the texture brightness affects texture quality as well as tracking steadiness. Observe the recommendations in the Table 3..

Figure 49. Color-camera brightness adjustment

The brightness is lower on the left and higher on the right (slider positions exaggerated for clarity).

Sensitivity¶

You can tune the Sensitivity of Artec 3D scanners if the application fails to reconstruct particular surfaces. Increasing this setting enables the scanner to more easily capture black, reflective, translucent and fine objects (such as human hair). The higher the sensitivity, the noisier the recorded surfaces will be. Higher values may also reduce the scanning speed.

Frequency for Capturing Texture Frames¶

Specify the frequency for capturing texture frames by using the corresponding spinner in the Settings dialog (see Texture-Recording Mode and Figure 144.).

Deactivating Scanner Flash¶

If circumstances prohibit you from using the scanner flash, follow the directions below.

Figure 50. Influence of ambient light on captured results.

On left: flash is turned off; ambient light is poor; results—dark texture. On right: flash is turned off; lighting conditions are improved; results—good texture.

Note that if you disable the flash, you should compensate by using bright ambient light. According to our tests, acceptable texture quality is obtainable with the flash disabled if the surface illuminance is at least 1 000 lux. Compare the models shown in Figure 50., which were recorded under different lighting conditions.

The following procedure captures the textured model without using the scanner flash:

1. Open the Scan panel and click the Advanced link
2. Turn off the texture flash by selecting the Disable flash bulb checkbox
3. Use good illumination. Avoid fluorescent lamps.
4. Click Preview and direct the scanner at the object
5. Adjust Texture brightness and Texture exposure time. In most circumstances, values should be as low as possible, because increasing the brightness also increases a texture noise, whereas increasing exposure time can blur the texture. Instead of adjusting sliders, try to further improve the lighting conditions.
6. Capture the scene
7. Perform required postprocessing as described in Data Processing to get a textured model
8. Adjust texture parameters for this fusion as described in Texture Adjustment. Pay particular attention to the Hue and Saturation sliders. The Hue slider allows you to correct unwanted texture color.

Tuning Exposure Time¶

You can alter texture exposure time in the Preview mode. Adjust this parameter in tandem with the Texture brightness. Increasing exposure time can blur the texture. Don’t alter the default value unless it’s necessary.

Disabling Texture Recording¶

Clear Don’t record texture checkbox if you don’t want to store texture information in your scans. It is located in the Advanced section of the panel and disengages both texture camera and texture flash in the scanner. Note that this option is unavailable for Artec EVA Lite. Don’t forget to select this checkbox once you have completed textureless scanning; otherwise, next time you want to start regular scanning the hybrid tracking mode could be unavailable.

Decreasing Scanning Speed¶

Artec EVA captures objects at up to 15 frames per second, whereas Artec Spider at 7.5. Default values ensure comfortable scanning with smooth movements. However, if you find scanning speed inappropriate, you can decrease it. In this case, Artec Studio will record fewer identical frames and register them faster. To this end, use the Scanning speed slider in the Scan panel.

Supplementary Settings¶

Customize scan names and starting number

by entering your own values in the Prefix and Start with fields. The software uses these values to create a scan title in the Workspace panel (see Figure 73., left). You can change the default values Scan and 1 to, for example, Capture and 14.

Set backing up scan data to disk

Trigger a capture mode that simultaneously records scanning results to a disk by selecting the Copy scan data to disk checkbox. This option is enabled when you’re working with an existing saved project (see Saving a Project) and can be useful when capturing large amounts of data on a computer with insufficient RAM.

Specify a delay (in seconds) before recording

using the Delay before recording spinner under the Advanced section of the Scan panel. The countdown begins as soon as you click the Record button. To eliminate the delay, set the value to zero.

Decrease specified operating-zone

by using the Near (mm) and Far (mm) sliders in Scan panel. Here you can only decrease range within the specified boundaries.

Specify the operating-zone boundaries (in millimeters)

By default, Artec Studio provides the correct values for the minimum and maximum limits within which the cutoff planes are to be positioned. These values are different for each 3D scanner model, and they ensure that you capture good-quality 3D data. If high accuracy is a secondary concern, you can manually adjust the depth boundaries, allowing you to capture objects using an Artec L scanner or third-party 3D sensors positioned closer to or further from the object than is recommended. To do so, select the Override default depth range checkbox in the Settings dialog in the Scan tab, then specify new boundaries for the scanning range (For more details about scan settings, see Capture).

Warning

Custom depth-range settings may reduce accuracy.