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Beginner Planeless Scanning Questions

Questions, problems, comments and tips regarding the 3d scanning process.

Beginner Planeless Scanning Questions

Postby Agarwals » Mon Mar 31, 2014 7:52 am

Hi everyone,

First thank you everyone for all the help on the forums, there's a lot of really good info here!

I have a few questions about my planeless laser scanning set up.

Hardware and Software: I am using a logitech C620 webcam and a Coherent Stingray Green 5mw adjustable focus laser. We are also using an Arduino Uno with the Katie software for Sven and the DAVID software with a stepper motor and an EasyDriver board.

Q1: We were able to get a reference scan working where it shows the rainbow effect on the depth map. To do that, we click record new motion and sync with camera. After the reference scan is done, we click erase and uncheck "record new motion". Then we click start to scan our actual object and the DAVID software immediately stops the scan. We can't figure out what we did wrong here.

Q2: I've been reading the Wiki a lot for the manual, however the wiki is tied to version 3.5 I believe. Is there any more guidance for version 3.9 (or the newer 3.10)?

Q3: In the laser and camera hardware forum, most people seemed to be getting motors with 1/8th stepping modes. I haven't yet been able to understand why you would want 1/8th stepping over full stepping, especially if the software is trying to step once per frame.

Q4: I just want to make sure I have the steps for planeless scanning correct. First, you must calibrate the camera. Once it is calibrated, you do not need to recalibrate, even if the camera is moved? Second, you do a reference scan with a corner to record the motion and this corner needs to extend over the entirety of the reference scan? Third, you can remove the corner and scan whatever object you want at any distance from the camera? And as long as you always start in the same position and dont move the camera/laser set up, you don't have to do more reference scans?

Thank you all again for you help!

Sharud
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Re: Beginner Planeless Scanning Questions

Postby WalterMo » Mon Mar 31, 2014 1:08 pm

Hi Sharud,

As soon as possible I will test planeless scanning with DAVID 3.10 and try to answer your questions. Since DAVID's SL came up most of us use the new technique. It's much faster. :D

To Q3:
1/8 micro stepping has a 8 times finer step resolution than full step mode. For each captured camera frame DAVID sends one motor step impulse (if 'Motor Speed' = 1 is chosen). DAVID doesn't „know“ what kind of stepping you use. Therefore each impulse will drive the motor shaft for one step: If full stepping, then e.g. 1.8°, if 1/8 micro stepping, then for the same motor 0.225°.
Of course if 1/8 micro stepping is used DAVID has to send 8 times more pulses for the same scan range. This will work "automatically", we only notice it by a 8 times lower scan speed (movement of the panned laser). If we like to increase the "laser line speed" we can set a higher number than '1' in DAVID for 'Motor Speed'. DAVID will then send this higher number of pulses for each camera frame.

By the way, do you have a gear attached to the stepper motor? If yes, what gear ratio?

Walter

X78GHY
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Re: Beginner Planeless Scanning Questions

Postby Agarwals » Mon Mar 31, 2014 6:35 pm

Thanks Walter!

I am using a gear with a 99.5:1 ratio. We actually need the scan to be pretty fast because we're trying to scan large objects. So maybe we shouldn't have gotten such a large gear ratio?
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Re: Beginner Planeless Scanning Questions

Postby WalterMo » Mon Mar 31, 2014 8:00 pm

First: Your gear ratio of 99:1 is OK. Best you chose at your EasyDriver ¼ or 1/8 step mode.

In the meantime I have done some planeless scans with DAVID 3.10.0 (64 bit). And all worked fine.
My equipment:
Camera: Modified Logitech C600 at 800x 600 @ 15 fps.
Motor scanner: 1.8° stepper with attached planetary gear (ratio 64:1). 1/8 micro step mode.

Workflow:
Chose: 'Motorized Laser Setup'. Set the right COM port. DAVID normally automatically finds the same port as which was used to upload the Arduino code. Check if a hook was set under 'Advanced Settings' (at top to find under the cogwheel symbol). Then 'Communication', 'COM', 'Enabled'.

Do the calibration of the camera (by bright ambient light, switched off laser). Then....

Go to '3D Laser Scanning'.
Adjust a fine laser line.
Set a hook at 'Record New Motion' (= reference scan). Chose a appropriate 'Motor Speed'. Set your self-built controller to 'Auto' (motor and laser).
Start the reference scan: No „rainbow“ colors behind the V-formed moving laser line are visible.
Stop this reference scan at the end of the scan range and start with the very same settings the 'object scan' (No hook at 'Record New Motion' and don't erase the just done reference scan!). No 'Stop' is necessary, DAVID stops at the same position where you had stopped before the reference scan. During the test phase simply scan the walls of the corner.

If the test object scan is ok, you can remove the corner and scan something at the same place where the corner was before. For a new object-scan erase the former one (after it was saved :wink: ).

You can move the scanner to any place you like but take care that camera and laser scanner (motor) do not change its position to each other! Both must be mounted at a stable rig (construction). Otherwise the reference scan with corner must be repeated.

Also objects which have another distance to the scanner as before the corner had, will be scanned. Of course best results will be achieved if the object is about at the same distance as the calibration was made before. Here cam and laser were best focused. And, because camera and laser are not „looking“ along parallel lines but are working together under the so called intersection angle, more far away objects cannot be „hit“ by both devices. But this is necessary for DAVID's triangulation method.
Attachments
TestLaserScanReference.jpg
Screen shot during the reference scan, upwards scan direction
TestLaserScanObjectscan.jpg
Screen shot during the object scan (simply the corner walls)
TestLaserScan3D_Object.jpg
Scan result of the corner walls, 1x interpolated, no texture
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Re: Beginner Planeless Scanning Questions

Postby Agarwals » Tue Apr 01, 2014 5:55 am

Thanks Walter for that guide!

I've still been having a few problems, the biggest of which is after I conduct a "Record New Motion", I get the nice rainbow on the depth map. However, then I click "scan" again without re-hooking the record new motion option and without erasing the recorded motion and the software starts the scan and then immediately stops the scan. We did some debugging and confirmed that the start "S" command is being sent when we click start scan and then immediately a stop "T" command is sent. Any ideas on what is causing this? What variable does DAVID look at when it decides how long to run the repetition scan for?

Thanks,
Sharud
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Re: Beginner Planeless Scanning Questions

Postby WalterMo » Tue Apr 01, 2014 9:41 am

Sharud,
Today I did several scans under these conditions:
DAVID 3.10.0, dimmed room light, scan direction upwards.

And I found:
During the reference scan (hook at 'Record New Motion') the depth map behind the line was not visible.
If the laser was set to 'Auto' at my controller the following object scan (with depth map) worked fine. Nothing was erased before and of course no hook at 'Record New Motion' was set.

'Auto' means that the laser is automatically switched 'on' by DAVID only during scanning, not when the laser line returns to its start position.

But if the laser was permanently switched 'on' by hand the object scan couldn't be started. This happened:
The motor started for about 0.1 second or less (upwards), then stopped and immediately started backwards by running over the start position. Then, after some degrees, it stopped, changed the direction to upwards and slowly exactly reached the start position. This behavior is normally a feature of DAVID to eliminate the gear's backlash. This happened reproducible again and again. Means no ordinary object scan could be started.

So I had to do a new reference scan (in 'Auto' mode) and all worked fine.
Today I will meet Sven and discuss this behavior with him.

Walter

PS. Have you exactly recreated my controller (ARDU 3) and do you use the 'Auto mode' for the laser?
viewtopic.php?f=6&t=2421&p=14641&hilit

Have you changed a parameter in the Advanced Settings?
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Re: Beginner Planeless Scanning Questions

Postby Agarwals » Tue Apr 01, 2014 10:26 pm

Walter,

That seems to be the problem we are having too as we do not have a switch set up for the laser, instead it is manually turned on by hand. It doesn't seem like ours goes upwards, downwards, and then upwards again to account for backlash (it only does the first upwards and downwards) however that could be due to us not having a few other things hooked up.

Our build is pretty stripped down, we have mainly implemented the motor control and we do not have an LCD. As Sven instructed, we set FORCE_REMOTE_CONTROL to true in the Katie software. So thus Auto mode gets set automatically through that. However our laser and camera are always on and we also hardcoded the g_speed (I believe it's called that) instead of setting up a speed potentiometer because we want to have as few hardware components as possible.

One other problem we're having is that the motor does not always return to the 0 position after a scan, however I believe that might be because we do not have a button set up on the analog in pin that the arduino is reading to know when to go back to 0. So we think the Arduino is sometimes reading that as high and sometimes as low. Do you agree with this conclusion?

Finally, after some testing today we made a work around for the repetition scan only going one step. In the advanced settings, we turned off the setting that auto stops the repetition scan when it believes it has reached the end of the reference range. Because of this, we have pretty much concluded that for some reason it is not remembering the reference range correctly.

Thanks again for your help!
Sharud
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Re: Beginner Planeless Scanning Questions

Postby WalterMo » Wed Apr 02, 2014 8:02 am

Hi,
Sven promised to take a closer look to our problems. He mentioned that the last DAVID updates have no changes regarding motor scanning.

To your controller:
If I were you I would exactly recreate my controller and upload Sven's 'Katie 1.1' . Or the a little bit modified version (by me) 'KatieB 1.1' for a smaller display of 2 x 16 characters.

A display isn't necessary for an automatic procedure by DAVID, only useful. The potentiometer for speed setting is only necessary for the manual mode. In 'Auto' mode the speed is determined by DAVID's camera frame rate.
If you don't have a 3-position-switch built-in for the motor functions (Analog pin 2) you should force its input voltage to 2.5V by using both 1kOhm resistors. (to simulate 'Auto' mode).

Walter

PS. For some people it's difficult to buy special components in their country, but mostly it's possible to find an alternative. I will help where I can.
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Re: Beginner Planeless Scanning Questions

Postby Sven » Wed Apr 02, 2014 7:43 pm

Hi,

Thanks for the report. I have found the problem and fixed it. Please try this beta version:
http://downloads.david-3d.com/software/DAVID_3.10.1.4413_beta1.zip

The problem was that the combination of motor scanning and the settings "GrabReferenceImageOnStart" (default ON) and AutoStopAfterRepetitionScan (default ON) caused a false AutoStop directly after Start when the laser was switched on before the scan.

Sven
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Re: Beginner Planeless Scanning Questions

Postby WalterMo » Wed Apr 02, 2014 8:53 pm

Thanks Sven,

Now it works, even with a permanently switched on laser.

Walter
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Re: Beginner Planeless Scanning Questions

Postby Agarwals » Tue Apr 15, 2014 8:51 am

Walter and Sven,

Sorry for the late response. Been testing out the new beta as well as improving our circuit. It works now! Thank you so much for your quick responses and quick fixes. We all really appreciate it!! :)

Thanks!
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Re: Beginner Planeless Scanning Questions

Postby DimL » Mon May 12, 2014 5:07 pm

Greeting Davidians! Since this is my first post, well met!
I have read many articles on the forum and you are all very helpfull and you are doing a great job! Thank you!

My institute assigned me a project to create a 3d scanner in order to get my degree. After some search i decided to go with David cause of the simplicity of the procedure. After some more reading i decided to choose Laser scanning and try to automate the procedure as much as possible.

So i am trying to recreate Walter's "Advanced Turntable" http://forum.david-3d.com/viewtopic.php?f=6&t=4291
and merge it with Walter's "Ardu3" http://forum.david-3d.com/viewtopic.php?f=6&t=2421.

Q1: I have chosen this stepper motor for the Laser: http://www.phidgets.com/products.php?category=23&product_id=3322_0
And this stepper motor for the turntable: http://www.phidgets.com/products.php?category=23&product_id=3303_0
You think they are up for the job? And second, do you know any dealer or manufacturer in Europe? Cause getting them from US is going to set me back about a month.

Q2: Do you think "Automated 360° Turntable Code" http://forum.david-3d.com/viewtopic.php?f=15&t=6005 can replace the advanced turntable? I am asking because i see that Automated 360 table was made for structured light scanning!

Q3: I already have in my hands an Arduino micro which is same to Leonardo and i would like to use it. Do the sketches from both Advanced Turntable or automated table and Ardu3 work with the specific Arduino? (i have already tested them by uploading them on the Micro, and no error)

Q4: As far from merging the 2 sketches, i understand that i have to set different pins in some parts of the code, apart from that, i just copy and paste the void setup of the first one into the 2nd one, and same for the void loop? I will not use any Lcd. (i am sorry for that question, but my coding skills are close to 0)

Thank you so much for your time,
Dimitris.
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Re: Beginner Planeless Scanning Questions

Postby WalterMo » Tue May 13, 2014 12:10 pm

Hi Dimitris,
First of all, good luck for your project!

To Q1:
Your chosen motors will do the job. Here is a German reseller:
http://nodna.de/Stepper-Motors

For the small motor choose this, it comes with a higher impediance (better for the Pololu). And it has a higher torque:
http://nodna.de/Stepper-Motor-Bipolar-2 ... -10V-500mA

To Q2:
I don't know, never tested.

To Q3:
I don't know, never used. This could be e.g. a question to the Arduino forum.

To Q4:
You told us that you don't have much skills in programming. So the best is to build up both devices separately, the scanner and the turntable, each with its own Arduino and to connect them. An output signal of the turntable-Arduino can trigger the laser scanner for the next new scan.

Walter

PS. Maybe there are better solutions possible.
Edit: Here are all European Phidgets resellers listed:
http://www.phidgets.com/docs/Dealers#Europe
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Re: Beginner Planeless Scanning Questions

Postby MagWeb » Tue May 13, 2014 11:33 pm

Without any testing:
@Q2:
I see no conflicts combining both. The "automated 360" simply is a code of "at which time should which action be triggered". That should work for automateded laserscanning as well as for SL. You'll only have to make sure that your laser moved back to its start position before the Arduino sends a "Start a new scan" command back to DAVID......
@Q4:
No programming skills? Hmm. similar to me starting this adventure... It should work to copy and paste stuff as long as you do it right :wink: . Don't hesitate to post some code attempts here. Maybe you'll find some helping hands.
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Re: Beginner Planeless Scanning Questions

Postby DimL » Wed May 14, 2014 10:53 am

Thank you very much for the information!
On the site Walter gave me, i found pretty much everything i need for my project!
I also found this: http://nodna.de/Base-Rotate-Kit-BR-KT-BR-NS in case someone else is searching for a ready-made turntable!
MagWeb thank you for your tips and most of all thank you both for being so helpfull !
I am tearing apart an old printer so i can experiment with its stepper motors before i connect the "big ones" !
I will keep you posted!
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