Particle Filter 3 - How to filter particles satisfying ALL criteria?

[mpu]

I am trying to filter a binary image to only keep particles that satisfy ALL of my desired criteria (e.g. within a specified range of Area AND Perimeter). The Particle Filter 3 vi keeps particles that satisfy ANY of the criteria (e.g. Area is in range but perimeter is out of range). Do I need to loop on Particle Filter for each criteria or is there another way to do this?

Thanks,

--Dave

[b.ploetzeneder]

Hi,

no, use the "Keep/Remove Particles" property and the "Exclude/Include" bool for the limits.

Example: You want to remove any particle with

an area from 0-100
AND a perimeter from 100-1000.

To do so, KEEP any particle that has

- an area from 101-+Inf
- a perimeter from 0-100
- a perimeter from 1000 - +Inf.

Birgit

[mpu]

Thank you, Birgit.

My original implementation was intended to KEEP particles that were within both Area and Perimeter limits.

Example: KEEP particles with Area from 100 to 200

AND Perimeter from 50 to 75.

I set my selection value measurements to:

   Meas Param=Area, Range Lower=100, Range Upper=200, Range=False (IMAQ Particle Filter 3 VI particle meets the criteria if Range Lower Value ≤ particle measurement < Range Upper Value)

  Meas Param=Perimeter, Range Lower=50, Range Upper=75, Range=False

In Particle Filter I set Keep/Remove to False (only particles meeting any of the criteria remain)

In my image I had 2 particles:

    1: Area = 150, Perimeter = 70

    2: Area = 25, Perimeter = 50

The result was that both particles were kept, even though particle 2 was outside the Area criteria. I don't understand why.

I then changed my implementation to EXCLUDE particles outside the Area and Perimeter ranges as follows:

I set four selection value measurements to:

   Meas Param=Area, Range Lower=0, Range Upper=100, Range=False

   Meas Param=Area, Range Lower=100, Range Upper=+Inf, Range=False

   Meas Param=Perimeter, Range Lower=0, Range Upper=50, Range=False

   Meas Param=Perimeter, Range Lower=75, Range Upper=+Inf, Range=False

In Particle Filter I set Keep/Remove to True (particles meeting any of the criteria are removed)

This implementation works. Can you explain why my first implementation did not? I would like to understand just how the tool works.

Thanks,

--Dave

[b.ploetzeneder · Accepted solution]

Hi,

I am not from NI so I don't see the internal implementation. However, I stumbled upon that when I quickly looked up the parameter in the help before I typed my initial answer. 

Correction of my previous answer, I was on my mobile and didn't read too closely.

You correctly identify that Particle Filter tries "any" condition, aka an OR condition.

Case 1:
1) Keep anything that is are 100-200
2) ALSO keep anything that is perimeter 50-75.

Case 2:
1) Remove anything that is area 0-100
2) Remove anything that is area 200-Inf
3) Remove anythng that is perimeter 0-50
4) Remove anything that is perimeter 75-Inf

It seems to do that sequentially.
 

Birgit

[mpu]

Thanks, Birgit. Your explanation for the second case that the tests are sequential and OR'd makes sense.

It does seem like a sloppy way of doing things but if I understand how it works then I can deal with. As you said, no loop is needed.

Thanks!

--Dave