first 3d scan

On this page I’ll try to keep track of my experimentations with 3d laser scanning.

I am using the freely available “DAVID” application. David is a free program that you can download from here. It will be going commercial at some point but for now it’s still free. To run the software you need windows and the .net framework. If you haven’t had a look at their pages yet, please do so now.

On this page I’ll explain what I’ve done to actually work with the software. See their page to find out about the software itself. Their documentation is simple and quite good.


Printing out the backgrounds

For now I just printed out the background images which you get supplied as .pdf along with the program on A4 paper. I am thinking of taking the files over to the copyshop to get them on A3.


 

Cutting the background images
Lucky for me… I have a proper cutter… but I’m sure scissors or a good knife will do as well. You want to be precise here. Someone asked me what the dots are for… I recon… they’re used to see how deformed the image the camera sees is. That way it can calculate the type of lens it has and counter it’s deformation (you don’t want a warped result)

 


 

Placing the background images

You want to line the images up precisely… otherwise the result won’t be neat… There’s really only one way you can place them. There’s two arrows right where you cut them, and you need to line those up. I glued them onto the background with basic glue, but added some tape to the seams. I think you really want thicker paper than the default printer stuff to get a real nice result, as long as it isn’t glossy.


 

Background construction

I actually removed two shelves from a cupboard in the basement to construct the corner… the shops were closed since was christmas time. Then I stuck some big white pieces of paper to them which I cut with a stanley knife. I placed a big white sheet of paper underneat. I’m considering getting some pre-cut mdf but that can wait.


 

Setting the background angle

You do really need to have the corner at a precise 90 degree angle. So I got a hook out and bent everything slightly. I think if you also create a floorboard you could do some nice slots for the walls, but I don’t mind checking with the hook right now.


 

Connecting the background

I happened to still have some metal corners lying around so screwed the shelves together using those. I think sticky tape may work, but You do want something solid to make things reusable. I really like the hinged method they use on the official site, so I may go for that once the shops open again. They said something about using the corners of you room, but apparently they haven’t been to my house 😉


 

The line laser

Apparently you can buy cheap laser levels at your local DIY (Do It Yourself) shops nowadays. I still had a laser line diode lying around. I bought it from apinex.com. The diode doesn’t come with housing or a power supply so I used an old power convertor. I’m not too knowledgeable about electrics but this is simple enough.


 

Constructing my laser housing

To make the laser more manageable I needed some sort of housing. So I took an old marker and cut the tip off (and removed the ink of course). I also cut the tip off the marker’s cap. Then I put the diode in the old marker’s cap and threaded the power supply’s wire through the marker’s body. After this I simply soldered the wires together. As you can see I can still remove the marker’s cap to get at the wires now whilst it’s basicly a laser pen. It might be a cheapass solution, but at 3am it didn’t look bad at all… and it works really well. I’m actually quite proud of it haha.


 

The camera

I had a crappy old creative webcam but that was simply not good enough. The image was far too grainy. At the institute they’re using a $250.- firewire camera, but I am only experimenting a bit so I went out and bought me an xbox 360 camera (yeah I got one of those as well). It’s basicly the same as a good microsoft usb webcam, costs the same too, and actually this one looks rather nice.


 

My first scan subject

So I needed to find something in my house to try to scan. On top of my tv I still had one of these neat little coffee makers (a company sent it to me last year as a christmas present, and I had no use for it yet, thanks guys).


 

Way too reflective

Now you can see if I put the laser on it it’s far too reflective. The laser is all over the place. The program will never be able to tell what to interpret.


The reflection solution

So to make it non reflective I took an old roll of masking tape and stuck it all over the coffee pot. Of course it’s really not efficient to do it like this, but I had it lying around. I’ll try clay models over the next couple of days.


 

Calibrating the scene

Now I had everything I needed I opened the actual David program. See screenhots and help on what button does what on the institute’s site. I took the camera’s setting off auto and basicly all I did was up the exposure and contrast to really make the black dots and circles stand out. You need quite a high contrast to auto calibrate. I tried the manual calibration but honestly… you don’t want that. Also I am only using: 352 * 288 pixels My camera will do more, but since David creates a vert for each pixel setting it higher will result in a more complex mesh… and for me… this is quite complex enough, especially for testing.


 

Placing the object to scan

I didn’t want to place the coffeepot on the floor because of the camera angle (it wouldn’t see the bottom properly) so I put it on top of the bottom half of a matryoshka. Yes I know… improvising all the way. Now do keep in mind, you need to still see some of the background dots to the left and right of your subject. Otherwise it really won’t work at all. It took me a while to figure out what those error messages meant 😉


 

Laser setup

Now you can see that the model was placed correctly and the calibration is done. You can also see here that I was holding the laser quite high (big slant of the laser on the sides). If you don’t hold the laser high enough you’ll get error messages. But the big issue here was the colouring. The difference between the laser and everything else was really not big enough.


 

Proper scan setup

So I needed a bigger contrast between the laser and everything else. Also the colour was not needed at all. Thus I set the exposure a lot lower to make the image darker, I killed the saturation to make it black and white and played with the contrast to get the result you see below.


 

Oooh scanning

So it’s time, I simply clicked on start in the application and waved the laser all over the subject. I just went up and down a bit. It’s real nice to see the scan appearing.


 

After recording the scan I clicked on smooth average once and then on interpolate, giving the result below.


 

Scan done

Then I clicked on show3d and behold… an object… Time to save to .obj and import into blender (my 3d application of choice).


 

Doing a test render

I imported the model into blender and removed some of the loose verts created by the scan. You can see a wire render on the left and a solid one on the right.


 

For the future

I’m going to “borrow” (cough) some clay from my mother tomorrow (she makes really cool pottery). Then I’ll do some more interesting sculptures to scan. Also sadly still missing from the software is the possibility to stitch multiple scans together, but I can live with that for now. I’ll leave it at that and will update this page later as I get better and or more interesting results

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