3D for Crazies

[jabuffi]

epineh is right, an excel spreadsheet would be great for this sort of thing. One route to the depth values is through vector algebra... Establish the vectors that describe the plane of the laser and the separationof the camera as well as the many many vectors of each pixel of the camera's CCD, then scan the image for which pixel has the proper color (the color of your laser) With a little algebraic manipulation, one can extract what the coordinates of the point on the scanned object from these vectors (quick simultaneous matrix solution in VB) and go on and on!!! Limit to number of scans/points/degrees of rotation per scan will be camera megapixel size, storage size on your computer for point data (and if you want to keep the pictures etc...) and the time you are willing to alot to a scan.

The trick is making the scanner accurate, or at least precise and then applying the proper "smoothing algorithims" to take out/minimize any errors....

[epineh]

Now I'm thinking what would be better, a rotating table setup or a moving gantry setup like a scanner, for the piece you are doing at the moment John, I think a gantry would produce better results. Hmmm looks like I gotta build two scanners now

Ha jabuffi, got your post while typing this, I agree the depth would be a pretty simple algebra calculation. If the angles between camera and laser is known and constant, it would be a simple trig function to calculate depth. Finally, we found a use for mathematics hehe.

I am going to make an enclosure painted matte black inside to house all of this, might help sorting out inteference from outside light and reflections.

So now the question... where the hell do we post a build log for this sucker ???

Here is another thought, it would be pretty easy to retrofit an existing router to carry a laser and camera, keep the feed rates down nice and slow to stop camera shake, I gotta stop now, my head is hurting...

Russell.

[epineh]

To answer my own stupid question, I guess we post a build log in the same category this thread is posted...

[greybeard]

So I come down to breakfast, log in only to find I got to start learning 3D algebra and how to use a spread sheet. I can feel one of my headaches coming on.
Saved by SWMBO also appearing for breakfast.

OK, I have a 50 year old memory of vectors, and I know what a matrix is, sort of, and that I casn use a spreadsheet to do the actual calculations oflots of data for me, but you're going to need to put it in pretty simple terms for me to keep up.

On the other hand, I still keep the dye-bath going as I can see that that could also be switched to the vertical mode and produce "in the round" scans.
Would it be possible to take say 6 dye-bath pics at 60degrees stepping, and "render " them onto the surface of a hexagonal column ?

[epineh]

So I come down to breakfast, log in only to find I got to start learning 3D algebra and how to use a spread sheet. I can feel one of my headaches coming on.
Saved by SWMBO also appearing for breakfast.

Hey... you started all of this, I was happy to start planning my 2nd router and possibly some projects for my first one, now I am looking around for material and spare steppers/drivers and planning layouts/concepts and software theories... oh yeah not to mention a 4th axis for my router to re-create the objects I intend to scan.

OK, I have a 50 year old memory of vectors, and I know what a matrix is, sort of, and that I casn use a spreadsheet to do the actual calculations oflots of data for me, but you're going to need to put it in pretty simple terms for me to keep up.

It has to be simple, or I'm out... I am only a dumb electrician remember...

On the other hand, I still keep the dye-bath going as I can see that that could also be switched to the vertical mode and produce "in the round" scans.
Would it be possible to take say 6 dye-bath pics at 60degrees stepping, and "render " them onto the surface of a hexagonal column ?

I'm not sure I get what you mean, but I think so, you want to copy something already hexagonal ? Mad if you don't. I am thinking of much higher resolution though, probably index half a degree at a time and have a vertical resolution of about 600 lines, it would be nice if my camera supported direct downloading to PC, sure would save time, although at 8 megapixel we are gonna burn some hard disk space... more power Igor!!!

Russell.

[greybeard]

I 'm hoping to try the hexagonal idea because the dye bath produces the xyz information without the need to scan. By taking the six shots the camera will see down into the depths of any pockets.
Sorry, I've switched from bas relief to "in the round" without drawing a breath.

The initial idea for the immersion method came from the desire to use a piece of software(Designer) that can import a greyscale jpeg and convert it to a bas-relief carving done using a raster scan type cut, with z proportional to %black.(I don't have the machine, just solving problems for others)

I can see, though, that if I can get the detail picked up, the principle might also work for cnc lathes if I could produce a surface that could be wrapped round a "primitive" - in this case a hexagon if I took six pics.

[greybeard]

Plastic figure about 4" tall immersed in black dye bath. I got a lot of dust on the surface of the liquid, so I've done a minimal editing on the image, then converted as before.
I think it shows progress, but still some way to go.
John

[CJL5585]

John,

Your projects are looking good. What kind of resolution do you think are you getting?

Jerry

[erase42]

i didnt read every single post here so sorry if this is already been mentioned or tried, but what if instead of milk, you used smoke or perhaps vapor from dry ice? it wouldnt have the same diffracting effect as the milk, and would perhaps preserve the sharp outines of the object. another thought is maybe with either the milk or the smoke, make it much more diluted, then take the photo and copy and superimpose it over itself many times in photoshop or paintshop etc. you would maintain the sharpness and still get your gradient.
Its all talk, someone let me know if it works.

Ed

[greybeard]

Hi Ed.
The fundamental problem with my original idea of using milk is that the fat globules that form the emulsion scatter the light(they might even fluoresce in the flash, but that's another story), and so add opacity.
The idea is to "add darkness" with depth, not opacity, so switching to a coloured liquid will do that.
The smoke/dry ice idea has the same limitation as milk, but with the added problem of non-linearity - it doesn't stay still, and uniform in density, so there's no correlation between depth and darkness.

Jerry - not sure about the resolution. I think "poor" is the nearest figure I can come up with.
I'm going to try and improve matters from two directions now. The first is the lighting setup, so that I can avoid using flash.
The second is to look at an old photo programme that I have somewhere that enabled you to add two images together, rather like Ed has just suggested, but a bit more advanced. It allows you to set up a boolean filter, so you can add only the darker areas for instance. I think Ed's idea is sound, but does the same as increasing the contrast in the normal way. This would have the effect(I tried it in the first set of images) of increasing the depth of the image for the carving software, but does nothing for the resolution.

Busy weekend ahead, so it may be a few days before the next instalment.
John

[10bulls]

B*STADS! You've all stolen my 3D scanner idea (not the milk one, that's just odd).

OK, here's my 2c worth...

1. 2 brackets on your toolmount, one for a laser, one for digicam.
(you already have a cnc machine up/down/alongy thing)
(every tool should have at least a couple of mounts).

2. A hi-res video camera would be best. Digital cameras are very slow
(well my piece of poo is). And need odd software or yucky TWAIN.

3. Capture video to an avi. (no special software needed).
as the machine scans over the 'thing'.
Bonus points for rotary axis useful but not necessary.

4. Insert aforementioned avi into a program that fits a nurb to the laser line in each frame. So for each frame (angle) you have a smooth line you can chop into data points anywhere you want. Build up an array them then even my mum could write a program to triangulate that!
You could do it without a laser if you want, just look for silhouettes.

5. Eat jelly and go play with wing wong.

[greybeard]

If you'd read more carefully, 10bulls, and been a bit more sensitive, you might have guessed that our wing wong died when we gave it too many jelly nurbs.

[10bulls]

Very sorry to hear that. Did I read that it was a European wing wong? You must have fed it wong jelly. I get my nurb jelly flown in from the Isle of Wight. So don't use Wong jelly, buy Wight jelly and watch your wing wong flourish.

[MrBean]

This is a very interesting thread.
I'm trying to get my wing wong airborne, but was told I got the wong wing.
I got the wight jelly, but need to know, Is this the wong wing for a wing wong?"

Cheers.

[greybeard]

No Terry, that's the Asian wing wong wing.
The European has a ring on.

John

[10bulls]

The European has a ring on.

Ah! So that's what went wrong with my winged wing wong!

OK, I'm off to put on my thong and go play ping pong with king kong then off for a sing song at the King John son.

(...now where's my bong gone?)

[10bulls]

When I first read this thread I thought senility had finally overtaken you greybeard. But who am I to judge! So in the spirit of experimentation...

Photo'd green man in a tray with blue food colouring (I think my hands may be stained for life!). I photochopped it a bit and made background blue.

OK, then I made a copy using only the RED channel. (If you've ever read 'The Deep', there's a good bit about the colour of blood at various ocean depths).

This last image was then stuffed into the CamBam heightmap plugin and hey presto.

Greybeard, you are quite possibly a genius!
Now all I have to do is persuade the kids to stay still under the bath water long enough while I go get the blue food colouring.

[epineh]

Looks like we need to go trade in all 3D modelling software for some trays, milk and assorted food colouring...

Hey John, are you the same Greybeard that has Blender tutorial videos on the Blender homepage? ... seems a strange coincidence.

Russell.

[greybeard]

Not me, unless there's something about me that even I don't know yet

I downloaded blender two years ago, but haven't unzipped it yet - perhaps it's time I did !

John

[epineh]

Ah well it was worth a try, and I was hoping to get some free lessons !!!

It is actually a fairly capable program (and free!!!), though I am not at all any kind of expert on 3D modelling, it seems reasonably useful to me, I'm sure I read somewhere it exports STL files if needed, I'm thinking of using it instead of AutoCad, since I have to learn from scratch anyway.

Currently downloading what tutorials I can find, I think it could be used to incorporate laser line profiles from a series of photo's / movie frames... I just have to figure out how to make SOMETHING first...

Russell.