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TDA4VM: VPAC LDC Projection

Myrah Naeem
Prodigy 40 points
Part Number: TDA4VM


Hello, 

I have corrected fish-eye Image 2D image like below using Mesh LUT but I want cylindrical projection of image rather than perspective projection. So, my question is does Mesh LUT, VPAC LDC or  DCC ISP TOOL supports cylindrical projection ? if yes, then what is the procedure ?

original image 

corrected image 

Kind Regards,

Myrah Naeem

  • +1
    TI__Guru 60030 points

    Hi Myrah,

    Yes, you may program the mesh LUT so that other projections or geometric transforms are implemented.
    The overall process is the same as we just walked through for fisheye correction (from fisheye --> rectilinear) in the other thread.

    Customers typically choose either of the following options:

    1. Use other s/w (e.g., opencv) to generate the back mapping coordinates and then down sample and convert to LDC mesh LUT format.

    2. Modify the matlab/octave script to implement a particular projection or geometric transform.

    Then, verify the LUT in DCC tuning tool, optimize for LDC parameters, export to xml format for H/W.

    Since you have all the necessary information about generating/encoding LDC mesh LUT, you may choose either of the above ways to implement your customized LUT.

    Best,
    Gang

  • 0 in reply to Gang Hua
    Prodigy 40 points

    Thank you very much gang, 

    I chose second option.

    I changed MATLAB code and implemented cylindrical projection successfully.

    Kind Regards,

    Myrah Naeem

  • 0 in reply to Gang Hua
    Prodigy 40 points

    Hello Gang, 

    I have created Mesh LUT with cylindrical projection but I want it to unwrap my whole image rather than just small area. My mesh is just acting on the center region and rest of the area is stretched. Can you please guide me which parameters should be changed to create Mesh LUT to unwrap whole region instead of specific area highlighted in the image?

    As you can see only central part is unwrapped rest is stretched 

    Kind Regards,

    Myrah Naeem

  • 0 in reply to Myrah Naeem
    TI__Guru 60030 points

    Hi Myrah,

    All information about the target geometric transform is included in the mesh LUT input for LDC.
    No other LDC parameters can help.

    It looks like you created a correct mesh LUT for TDA4 LDC, since the output image is smooth and artifact-free.
    Just that you are not sure what geometric transform you would need to start with.

    You should be able to find some opencv examples by googling.

    Best,
    Gang

  • 0 in reply to Gang Hua
    Prodigy 40 points

    Hello Gang, 

    I think my question was not clear enough. I just want to know why the region around checkboard is stretching in the Mesh LUT created by TI method? 

    Kind Regards,

    Myrah Naeem

  • 0 in reply to Myrah Naeem
    TI__Guru 60030 points

    Hi Myrah,

    >> why the region around checkboard is stretching

    I am not sure if I understand your question correctly.
    The geometric transform we can possibly do with 2D imaging without depth information is from 2D to 2D.
    Any thing that is out of a 2D plane are subject to perspective distortion.

    Best,
    Gang