Hey Guys,

My name is Anhar and as a personal project I’ve been trying to build a simple head tracker, after Googling this is the closest I’ve come to it (excluding TrackIR and FreeTrack, since they do not show their source codes)

I need to ask for some guidance, I was trying to code my own program using a webcam (with film filter) and some LEDs.

I’ve broken the problem down as thus far:

(1) Initial Blob detection greyscale line scanning (thresh holding)

(2) Generate Centroid (using intensity weight based method)

(3) Implement POSIT algorithm << --- (This is the problem)

The first two parts I understand how to implement in terms of coding, the last POSIT algorithm is what I’m having trouble with.

I have read up on Daniel DeMenthon papers (POSIT in 25 lines of Code), the problem is I don’t understand the maths clearly enough, they don’t have a numerical example, and my memory of Matrixes is really fuzzy

The bits I do understand thus far, is that one takes the 2d points from the CCD/CMOS in pixels, this is the “screen co-ordinates” and then projects this back to reach the real world points, I guess this is the SOP part (Scale orthographic Projection) and then somehow you can then calculate the pose from this which is the POS part (Pose from Orthographic Projection) after that you just iterate to reduce the error.

Can some one please give a step by step Numerical example of how this is calculated, that’s all I need, once I understand that and how its actually calculated I should be able to code it.

I’m sure this would also serve as a tremendous source of help for other wishing to code their own stuff.

Thanking you in advanced

Anhar

My name is Anhar and as a personal project I’ve been trying to build a simple head tracker, after Googling this is the closest I’ve come to it (excluding TrackIR and FreeTrack, since they do not show their source codes)

I need to ask for some guidance, I was trying to code my own program using a webcam (with film filter) and some LEDs.

I’ve broken the problem down as thus far:

(1) Initial Blob detection greyscale line scanning (thresh holding)

(2) Generate Centroid (using intensity weight based method)

(3) Implement POSIT algorithm << --- (This is the problem)

The first two parts I understand how to implement in terms of coding, the last POSIT algorithm is what I’m having trouble with.

I have read up on Daniel DeMenthon papers (POSIT in 25 lines of Code), the problem is I don’t understand the maths clearly enough, they don’t have a numerical example, and my memory of Matrixes is really fuzzy

The bits I do understand thus far, is that one takes the 2d points from the CCD/CMOS in pixels, this is the “screen co-ordinates” and then projects this back to reach the real world points, I guess this is the SOP part (Scale orthographic Projection) and then somehow you can then calculate the pose from this which is the POS part (Pose from Orthographic Projection) after that you just iterate to reduce the error.

Can some one please give a step by step Numerical example of how this is calculated, that’s all I need, once I understand that and how its actually calculated I should be able to code it.

I’m sure this would also serve as a tremendous source of help for other wishing to code their own stuff.

Thanking you in advanced

Anhar