Dear DAVID Community,

As you are probably aware, the entire DAVID company, team and product range has been integrated into HP Inc.
This forum is now read-only. Relevant content has been migrated to HP and merged into HP's Support Forums on November 1, 2016.

To start new discussions for 3D Scanning, please register and post your new topic at the HP Support Forums

Calibration Panel - left and right inner point

The place for questions, problems, comments and tips regarding the camera calibration.

Calibration Panel - left and right inner point

Postby sts » Mon Jul 07, 2014 4:01 pm

Hello,

i've use david (with SLS-2 Kit) for a while now, but now i wanna scan larger objects with a larger panel.

i've taken the original calib panel and was surprised that the distance between the inner points from the left and right panels to the the corner are not half the distance from the other points.

The distance is much larger at a 240mm panel it is not 60mm as i expacted, it is 70mm.

Image

i mean, the distance from red line is smaller than the distance from the green line. The printouts in the package are on the same distance.

Is this important? Is this unimportant? Does daivd even care?

Thank you,
sts
sts
 
Posts: 16
Joined: Fri Jun 27, 2014 1:35 pm

Re: Calibration Panel - left and right inner point

Postby WalterMo » Mon Jul 07, 2014 6:23 pm

You have to cut the calibration sheet along the vertical (y) line.

Have a look to the DAVID file 'Calibpoints_V3_A4.png'. It is in the folder 'printout' and came with the DAVID software.
This file has the left and the right side on one sheet of paper.
User avatar
WalterMo
Moderator
 
Posts: 2363
Joined: Mon Apr 02, 2007 6:52 pm
Location: Braunschweig, Germany

Re: Calibration Panel - left and right inner point

Postby sts » Tue Jul 08, 2014 7:27 am

Yeah, i know. But at the original David SLS2 glas calibration panel is a difference betwenn the the distance of the points on one side of the panel and the inner points on both sides of the panel.

In the advanced settings i have found the parameter:
ExpectedPlaneOffsetsOfOuterCorner

Is that a way do modify the range between the inner points? And what value i have to set?

My distance between the points on one Panel are 103,38 mm. Half way is 51,69 mm.
My distance between the inner points and the corner are 55,74 mm.
So the way is 4,05mm longer per side than on one side.

Thank you,
STS
sts
 
Posts: 16
Joined: Fri Jun 27, 2014 1:35 pm

Re: Calibration Panel - left and right inner point

Postby sts » Tue Jul 08, 2014 7:34 am

MagWeg wrotes:
"ExpectedPlaneOffsetsOfOuterCorner" value="yourValue" (it it should be: (measured distance between the markers' centers next to the edge and the edge)-Scale/8 )

So:
measured distance between the markers' centers next to the edge and the edge = 55,74 mm
scale = 413,51 mm (4 * 103,38)

So its: 55,74 - 413,51 / 8 = 4,05125

Is it right to set the value from ExpectedPlaneOffsetsOfOuterCorner to 4,05125?

sts
sts
 
Posts: 16
Joined: Fri Jun 27, 2014 1:35 pm

Re: Calibration Panel - left and right inner point

Postby MagWeb » Tue Jul 08, 2014 8:33 am

Hmm, not sure about this... never saw this new glas corner til now.

Different distances may be caused by its construction.
e.g. this:
Attachments
Offset.jpg
MagWeb
Moderator
 
Posts: 2499
Joined: Wed Jul 18, 2007 8:48 pm

Re: Calibration Panel - left and right inner point

Postby sts » Tue Jul 08, 2014 9:38 am

The panel looks like the attachment.

On the 240er scale is the distance between two points 60mm.
The distance from the inner point to the edge of the glas is half way, so 30mm.
But the two panels doesnt fit together, there is a gap. So there are 3,9 mm from each point to the the virtual corner of the panel.

My question is: Does David correct this automatically? Must i set some parameter?

Thany you very much,
sts
Attachments
calib_panel_sls2.png
sts
 
Posts: 16
Joined: Fri Jun 27, 2014 1:35 pm

Re: Calibration Panel - left and right inner point

Postby sts » Tue Jul 08, 2014 10:09 am

The setting ExpectedPlaneOffsetsOfOuterCorner is for outer/ negative corner, is there a setting like this for the inner/positive corner?
sts
 
Posts: 16
Joined: Fri Jun 27, 2014 1:35 pm

Re: Calibration Panel - left and right inner point

Postby MagWeb » Tue Jul 08, 2014 10:17 am

With no SLS-2 at hands:
If you set HardwareSetup/SetupType to DAVID SLS-2 all should be fine.

The only AdvancedSettings parameter to compensate this gab for a inner corner is AdvancedSettings/Camera/Calibration/CompensatePatternOffsets (should be active by default)

Right:
ExpectedPlaneOffsetsOfOuterCorner is meant for a "negative", convex corner only and is 3.9+glas in your case.
MagWeb
Moderator
 
Posts: 2499
Joined: Wed Jul 18, 2007 8:48 pm

Re: Calibration Panel - left and right inner point

Postby sts » Tue Jul 08, 2014 10:29 am

- SetupType is David SLS-2
- CompensatePatternOffsets is active (and the compensate for my larger panel is propotional smaller than the SLS-2 Panel and only slightly larger absolute, so it should work).
- So ExpectedPlaneOffsetsOfOuterCorner doesnt fit for me.

In the Advanced Settings i've found:
HardwareSetup - Left/Right-CalibrationPattern - Offset_X
HardwareSetup - Left/Right-CalibrationPattern - Offset_Y
HardwareSetup - Left/Right-CalibrationPattern - Offset_Z

Can this setting help me? Or should i position/make both panels that they have to the corner half of distance from point to point?

sts
sts
 
Posts: 16
Joined: Fri Jun 27, 2014 1:35 pm

Re: Calibration Panel - left and right inner point

Postby MagWeb » Tue Jul 08, 2014 10:47 am

You could set
offset_z to 3.9 for the LeftCalibrationPanel
and
offset_x to 3.9 for the RightCalibrationPanel

But I cann't imagine that you've to do this using SLS-2 hardware and its preset.

BTW: Do you have any problem to calibrate with SLS-2 default settings or some bowed results?
MagWeb
Moderator
 
Posts: 2499
Joined: Wed Jul 18, 2007 8:48 pm

Re: Calibration Panel - left and right inner point

Postby sts » Tue Jul 08, 2014 12:33 pm

I'll try this, thank you.

The calibration is no problem (around 20°). The quality of each scanning looks fine. But i think the results, as you say, bowed. The alignment dosent fit. On one end its okay, on the other end i have large diffence between the scans. If i try to point align the messy part, it goes okay, but the problem swaps.

The scan is an quick and dirty scan, with some settings i've tested and low corrections. The object fits completly in the scan area.

sts
Attachments
heat_pipe1.png
sts
 
Posts: 16
Joined: Fri Jun 27, 2014 1:35 pm

Re: Calibration Panel - left and right inner point

Postby MagWeb » Tue Jul 08, 2014 1:02 pm

To check whether your results are distorted:
-Do a fresh calibration (best with all settings at default)
-Do not (re)move the corner but use it as an object to be scanned.
-Scan it
-With the result being visible (still in StructuredLight mode) hit the CalibrationCornerVisibility toggle (first button in the upper Visibility menue) to display a virtual version of the corner. Compare it with your scanning result. Note: This will never match 100% but there should be no bigger offsets.

Maybe you post a screenshot of this scene.
MagWeb
Moderator
 
Posts: 2499
Joined: Wed Jul 18, 2007 8:48 pm

Re: Calibration Panel - left and right inner point

Postby sts » Tue Jul 08, 2014 1:55 pm

I'll give it a shot, when i am able to use the scanner next time.

sts
sts
 
Posts: 16
Joined: Fri Jun 27, 2014 1:35 pm

Re: Calibration Panel - left and right inner point

Postby sts » Tue Jul 08, 2014 4:13 pm

I have done the reset of the config. Done a brand new calibraion. Scan the calib panel.

I think they are quite oy. Some flickering.

Here are the screenshots:
calibscan1_front.png

calibscan2_back.png

calibscan3_top.png
calibscan3_top.png (9.25 KiB) Viewed 4243 times


I rescanned the pipe and the result isnt significantly better than the one above.

sts
sts
 
Posts: 16
Joined: Fri Jun 27, 2014 1:35 pm

Re: Calibration Panel - left and right inner point

Postby MagWeb » Tue Jul 08, 2014 4:51 pm

That looks very good. Seeing this, I don't think there's a calibration problem and your partial pipe scans should be right too...

Think it's an aglinment problem where DAVID finds a "better" fit of the to regular surfaces if it sets another orientation than the right one.
Did you try to use ContactPair? - Maybe you could apply some 3D markers on the surface (some dots of clay or something)? That makes it easier to find corresponding matching points on the partial scans.
MagWeb
Moderator
 
Posts: 2499
Joined: Wed Jul 18, 2007 8:48 pm

Next

Return to Camera Calibration

Who is online

Users browsing this forum: No registered users and 1 guest