HASH ID creation

Download pass3d release or build it yourself from the source code.
Requirements: OS Linux

Grid2d is the first recognition algorithm suggested by Michael Co.
Join the discussion here >> Make your suggestions about new algorithms to add and get rewarded from 3DPass contribution program.

• The input is a 3D scan/model of the object (.stl or .obj formats required).
  For example, you can download these two ones:
  pir1.obj and pir2.obj
• The output is a top10 hashes list inherent to the object shape

USAGE:
      pass3d --algo  --grid  --infile  --sect 
OPTIONS:
     -a, --algo         3d hash algorithm Algorithm. Supported algorithms: Grid2d
     -g, --grid         Number of cells in Grid2d algorithm
     -i, --infile     The path to the file to read
     -s, --sect         Number of sections in Grid2d algorithm
             

The object shape is considered to be recognized if there is at least one hash-value match among two different processing results. We have to process two or more different 3D scans of the same object and to compare the top10 results. We should use exactly the same parameters every time. It's recommended to use the same equipment, as well.

For example, we have two different 3D scans pir1.obj and pir2.obj of the same real physical object. In order to run the processing and create hashes from the first scan we have to run a command like this:

./pass3d -i pir1.obj -a grid2d -g 8 -s 68      
              

The output will be like this:

~/Desktop/3dpass$ ./pass3d -i pir1.obj -a grid2d -g 8 -s 68
Select top 10 hashes
"9bccac20a0586638cc74a2ff295c987d470794f24f008b02ce02643d0281f03f"
"11c41b6b30b191a2d61ae803d48cc42e83f9fdaac730665b24e3272672133efd"
"6f37f712139012d1c118cadea3a44b0535fa6b4b1272b1da49af3eb6498011f6"
"4453ed1aa4dabe394a0cedd79f8edb0940fb43a5558fbfa89ce56dad3fc8876c"
* --> "aa4019c8c160da9d2af69edc19589aabd925bc696966b967f92b71947f75f8f0"
"090ae6b23e2192fa4c2fb40cddad6e8537e2b437c49ff9fb227cf32c4e4085fc"
** --> "dd227121b91adcb5beabb0be9412613ebdfde8c5660301eb17583fa644b8793d"
"880cfda2b4811bf2ff1fe3ab92b38e64fc134d98c3dc8764eb8641a477b77a47"
"15cc9ef656a14c9ffde999512d11bd81cd5eaedaa81139a61847d470ea01043b"
*** --> "543e1c3929ea810f4e8c7cfc27f0b60df21a9374089f2278617dae327e32b034"         
              

The second scan processing outcome gives us this:

~/Desktop/3dpass$ ./pass3d -i pir2.obj -a grid2d -g 8 -s 68
Select top 10 hashes
"72592f8f6ea67c60ca7d9c7683256c3636a30be464952eb82996bff52ca4415d"
"3720e731b9aa04b08d83de34a796cbc389fce2c62365c68206c5610106db053d"
"a65008cdc77f72b47eda70e7c2eb57f93e4fffde5a5356549ac7dbf5d422dffa"
"5930d4a4a98ddff21997daaa8410b151f85dcdb7bfe6b0fb1a05af0e99c276fc"
"6846a36abb6dc50df6845627e6553ede8337e7350254ae8d02b7b7a696c79192"
"b20cf89afb10f14795afe517c82d7f6185da840e6035c48b488792e2df61846d"
* --> "aa4019c8c160da9d2af69edc19589aabd925bc696966b967f92b71947f75f8f0"
"deb83d22570bfc07b8881618dc34a6624616521475bac17798b7348cf6684fd1"
** --> "dd227121b91adcb5beabb0be9412613ebdfde8c5660301eb17583fa644b8793d"
*** -- > "543e1c3929ea810f4e8c7cfc27f0b60df21a9374089f2278617dae327e32b034"
              

Within those two processing results above there are three of top10 hash-values matched (they are marked as *, **, ***) So, we have the object recognized.

If we had three or more different 3D scans of the object processed, we could've picked up the most stable one Hash ID, meaning it's definitelly existing among the top10 hashes of every 3D scan we have. The more scans you process the more likely the best stable Hash ID you get. But practically it's enough to do 3-5 scans to choose. Sometimes you have no choice because there is only one hash is matched. If you have your 3D scanns in pretty good quality and it's assuming that the next ones are goint to have the similar, then you can pick up all of the hases matched. In our example it would be a combitation of theese three hashes:

* --> "aa4019c8c160da9d2af69edc19589aabd925bc696966b967f92b71947f75f8f0"
** --> "dd227121b91adcb5beabb0be9412613ebdfde8c5660301eb17583fa644b8793d"
*** -- > "543e1c3929ea810f4e8c7cfc27f0b60df21a9374089f2278617dae327e32b034"
                

Parameters adjustment

These are two key parameters we need to adjust in order to create the best possible Hash ID depending on 3D scans quality.

-g, --grid         Number of cells in Grid2d
-s, --sect         Number of cross-sections in Grid2d
                

Number of cells parameter -g:

Grid (-g) is the parameter which is about to help us to adjust the recognition algorithm to the particular 3D scan quality. The higher scan quality we get, the higher number of cells in the row we can set up for the processing. According to the Grid2d algorithm, by means of increasing number of cells, we are following a 3D scan cross-section contour more closely to the actual curve. That means that more precisely we can recognize the object shape. But, simultaneously, we're keeping less space for some error in the future. It's all about the balance between accuracy of the shape recognition and the ability to get the stable Hash ID.

Low definition scanners, especially smartphone apps, gives us a lot of error between two random scans taken from the same object. But High definition and professional ones might roll out not much than 3 micro meter error. So, it is recommended that we get several 3D scans made by the same equipment and then set the number of cells as hight as possible, provided it still rolls out successful recognition results. That is going to be the best set up. It might takes some attempts to adjust the optimal (-g) parameter’s value according to the scan quality.