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faq:en_problems

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Scan Problems and Solutions

My scans are noisy

  • This page of our User Manual shows good camera images.
  • Make sure your camera is as close as possible to the object, so that the object nearly fills the whole camera image.
  • Camera properties: Decrease the gain value (for most cameras to minimum), instead increase the exposure time, or better, the mechanic aperture size.
  • Camera properties: Try different exposure times and aperture sizes.
  • Make sure your camera does not use lossy image compression. E.g. for the Logitech Pro 9000, set to 800*600 at 15 FPS, not 30 FPS. Or 1600*1200 at 5 FPS, not 10 FPS. Details see here.
  • Hold the laser further away from the camera (usually: higher).
  • Use a better camera.

My scans are wavy

  • Move the laser slowly and steadily.
  • Keep the laser at one position and rotate it only.
  • Make sure your calibration panels are perfectly flat and in a precise 90° angle.
  • Hold the laser further away from the camera (usually: higher).

My scans are noisy

  • This page shows a good setup and camera images.
  • Make sure your camera is as close as possible to the object, so that the object nearly fills the whole camera image.
  • Camera properties: Decrease the gain value (for most cameras to minimum), instead increase the exposure time (or the mechanic aperture size).
  • Increase “Projector Brightness” in DAVID.
  • Make sure the red sine curves are not too low. Increase camera exposure if necessary.
  • Decrease environment light so that when you cover the projector lens with your hand, the camera image gets (nearly) black.
  • In DAVID, select a better SL Pattern Parameter profile (e.g. “Quality”).
  • In DAVID, go to Settings → Advanced Settings → StructuredLight and increase the NoiseReduction value.
  • Try a larger intersection angle (i.e. a larger distance between camera and projector).
  • Use a better camera.
  • As a last step, use the Smooth Average or Smooth Median filters.

My scans are wavy

  • Make sure the red sine curves are not distorted, i.e. they should not be cut off at the blue lines anywhere in the camera image. Please look at the pictures here.
  • On shiny objects, avoid direct reflexion of the projector light in the camera. You may have to cover the object with coating spray.
  • The camera's exposure time must fit to the frame rate of the projector (usually 60 Hz, so set the exposure time to 1/60s). When the camera looks at the projection, the camera image must be constant, no flickering/pulsing. The red curves must not move up and down.
  • Make sure the complete scene is still: The object must not move (e.g. breathing person) and camera+projector must stand still too.
  • Make sure the environment light is constant and not flickering (avoid fluorescent lamps).
  • In the projector's menu, make sure all filters are neutral, there should be no artificial contrast or brightness enhancement, etc. Especially, keystone correction must be set to 0 (off).
  • The projector should be set to its native resolution.

I want to scan faster

  • Make sure your camera is as fast as possible (highest FPS setting). Often you can get a faster FPS setting when reducing the resolution.
  • Select the “Speed” profile in DAVID3 (Structured Light menu).
  • Use a fast computer.
  • Use Windows Vista or 7 or 8, and make sure that Aero is activated.

My object is partly dark and partly bright

Use the Projector Brightness Slider in DAVID to adjust.

  1. Set up your scanner brightness settings for the dark surface regions.
  2. Reduce the Projector Brightness for calibration with the white panels.
  3. Scan the object, the scan will include only the brighter surface regions. Save the scan, and/or add it to the list.
  4. Increase the Projector Brightness again, the next scan will then capture the dark surface regions.
  5. Combine the scans in Shapefusion. If you have not moved anything between the scans, alignment is not necessary. If there are faulty scan data, increase the “Quality Check” filter value, or remove them with the Cleaning Tool in Shapefusion.

General

My scan is too smooth / missing fine details

  • Make sure your camera is as close as possible to the object, so that the object nearly fills the whole camera image.
  • Make sure all components (camera and laser/projector) are perfectly focused on the object surface.
  • Laser: Use a laser with a thinner line (adjustable focus!). Green is thinner than red. Blue is thinner than green.
  • Projector: Use one with a higher resolution.
  • Use a higher camera resolution.
  • Use a better camera / lens.

My scan shows outliers (3D points or fragments around it)

  • Make sure the environment light conditions are perfectly constant during each complete scan.
  • Make sure the environment light is significantly lower than the laser/projector light.
  • Avoid any movements in view of the camera, e.g. behind the object.
  • Laser: Avoid fast movements, also at the beginning and the end of the scan.
  • On shiny objects, avoid self-reflexion of the laser/projector light. You may have to cover the object with coating spray.
  • For SL scanning, you can define a scan range (minimum and maximum object distance from the camera) at Settings → Advanced Settings → StructuredLight → ResultFiltering. Just don't forget to reset these for your future scans…
  • If you really can't avoid outliers, you can delete them in the Shapefusion menu. You can clean each scan individually, or all together.
  • In the last step, Fusion, small outliers will disappear automatically.

Shapefusion: The alignment gets totally wrong

DAVID finds alignments that are mathematically good (lots of overlapping), but that may not be the desired alignment in some cases.

  • Start the alignment again, it is based on a randomized algorithm, maybe it gets right this time.
  • Use “Contact Pair Selection” to define one pair of contact regions by mouse.
  • Make sure the neighbor scans overlap by at least around 30%.
  • If the object has been rotated around the vertical axis only (parallel to the calibration corner), use the “Around Y Axis” mode.
  • If the object has a distinct texture (or you can paint some lines etc. on it), grab a texture with each scan and select “Use Texture” during alignment.
  • If you know the (approximate) angle of rotation, enter it in the “known angle” field (try positive and negative).
  • If nothing else helps, align the object manually by mouse (keep the CTRL key pressed and move/rotation with the left/right mouse button). With a little practice this will take only 10-20 seconds. When you have achieved a rough alignment, use the “Pairwise Fine Registration” mode to make it perfect.

Shapefusion: The alignment gets imprecise / the scans seem distorted

  • Make sure your scans are not distorted, i.e. the calibration was correct and the camera (and calibration panels or projector) have not been moved after calibration.
  • Make more scans, so that neighbors overlap more.
  • If the object has a distinct texture (or you can paint some lines etc. on it), grab a texture with each scan and select “Use Texture” during alignment.

The texture is not nice

  • Create a uniform ambient environment light for texture grabbing.
  • If the colors are wrong, make sure the White Balance is correct.

My 3D object has a wrong scale

  • When calibrating your setup, make sure you enter the correct scale length before clicking “Calibrate”.
  • The 3D data will be in the same unit as the scale value which you have entered (usually mm).

The resolution / file size of my scan data is too high

  • Fuse your scans with a lower “Resolution” setting (but do not re-fuse a Fusion result, instead restart Fusion with your aligned scans).
  • Import the fused scan into Shapefusion's List of Scans. Right-click on its name in the list and choose “Reduce Mesh Density”. Then save it again (save button below the list) - do not fuse it again.

Bug / Crash / Strange behavior

  • Make sure you have the required Microsoft .NET Framework (32-bit: 4.0 or newer. 64-bit: 4.5 or newer) installed.
  • In Settings → Advanced Settings → Service, activate the Debug Console. Take a look whether there are any helpful messages in the console window.
  • Take a look at the Bug Report section of our forum. If the problem has not been reported yet, please do so.
  • The most frequent problem is DAVID getting out of memory (RAM or OpenGL). Use a 64-bit system. Do not work with too many scans at the same time. Due to memory fragmentation it may help to re-start DAVID from time to time.
    Also please save your work (single scans, or aligned scans in the list) to OBJ from time to time.

My USB key is broken. What should I do?

Please contact us and describe the problem. Is the USB drive readable? Do you get any error messages? Have you tried it in another computer?
If it is possible to format the USB key, you can do that. Please contact us, we will help you restore the DAVID software (by download) and license (by e-mail), then the USB key does not have to be sent by mail.
If the key is broken beyond repair, please contact your dealer.

License

In DAVID3, you can see the license state in the menu “Help” → “License Info”. In DAVID2, you will get information when trying to save any scan on the Shapefusion page.

„No license file“

DAVID 2.x

The license file name is “license.dat”. It must be located in the same folder as the DAVID.exe (usually C:\Program Files\DAVID-Laserscanner or X:\DAVID\ on a USB key).

DAVID 3.x

The license file name is “DAVID3_license.lic”. It must be located in the same folder as the DAVID3.exe (usually C:\Program Files\DAVID-Laserscanner3 or X:\DAVID3\ on a USB key).
Since version 3.4, DAVID3 can also be run from the HDD without license file, it will automatically look for USB drives and look for a X:\DAVID3\DAVID3_license.lic there.

„License file not valid“

USB version

Make sure your USB key is plugged in and the license file is available in \DAVID3\DAVID3_license.lic.

Single PC license

If you have migrated to a new computer / operating system, we will have to exchange the license file. Please send an e-mail to sales@… with your new Registration ID copy+pasted as text.
DAVID 2.x: You can find your Registration ID by starting DAVID on your new computer, click “Next” 4 times.
DAVID 3.x: You can find your Registration ID by starting DAVID on your new computer, and opening the menu Help → License Info.

faq/en_problems.txt · Last modified: 2014/06/06 18:38 (external edit)