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Thread: OMA Trace File

  1. #1
    Master OptiBoarder MakeOptics's Avatar
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    OMA Trace File

    OMA uses polar coordinates to map out a traced shape, I understand and am having fun tinkering with these shapes. I have a question though, how do you curve back in on oneself since you can't have two radii at one axis? I have a sneaking suspicion that I could use drill coordinates with the very same file to route out the shape with the actual "R=" data used for the outer rough shape. Is this how it's done?

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    RETIRED JRS's Avatar
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    convert to X/Y change the length your after and convert back to polar
    J. R. Smith


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    Curious question: if the file only uses polar coordinates (ie 360 degrees, X-Y conversion), how does it handle highly curved data, for example in a wrap frame? Seems to me that the Z coordinate is needed as well, otherwise you have a flat trace, which would tend to skew any frame that does not have a 4 base standard "curve".

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    RETIRED JRS's Avatar
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    Z would be important if the intent is to modify the shape (not just check thickness points) - e.g. lens curve/frame curve @ bevel position. Most tracers at a minimum are 400 radial points (grad) and many now go to 1200 points. It's fun to plot the relationships between all the areas needed to fit lenses in frames.
    J. R. Smith


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    Yeah, JR, that's exactly what I'm talking about. A lot of wrap frames are 6 and sometimes 8 base, and then there are the flat frames designed for round lenses. Seems to me that if a lab is going to do edged jobs without a frame and rely on the trace data only, on some of these "odd" frames, there is going to be a fit problem with the bevel.

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    Objection! OptiBoard Gold Supporter shanbaum's Avatar
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    The standard comprises Z data as well. It is only now possible to define shapes that have inside cuts, by allowing more than one radius at a given angle, and by allowing a series of angles that do not invariably increase (that's in version 3.09 of the standard, which is about to be released).

    Notches and rectangles in the edge have long been handled as drill features.

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    Master OptiBoarder MakeOptics's Avatar
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    Quote Originally Posted by shanbaum View Post
    The standard comprises Z data as well. It is only now possible to define shapes that have inside cuts, by allowing more than one radius at a given angle, and by allowing a series of angles that do not invariably increase (that's in version 3.09 of the standard, which is about to be released).

    Notches and rectangles in the edge have long been handled as drill features.
    Thank you that is the answer I was looking for.

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    ABOM Wes's Avatar
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    Click image for larger version. 

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    Our Optronics 4t sends the Z data as well.
    Last edited by Wes; 09-28-2012 at 11:17 AM.
    Wesley S. Scott, MBA, MIS, ABOM, NCLE-AC, LDO - SC & GA

    “As our circle of knowledge expands, so does the circumference of darkness surrounding it.” -Albert Einstein

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    RETIRED JRS's Avatar
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    There are many things you can do to a trace shape (before actual edging) that impacts the final edged outcome... if you have all the required data. And not all of it comes directly from a tracer.
    J. R. Smith


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    Master OptiBoarder MakeOptics's Avatar
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    Quote Originally Posted by shanbaum View Post
    The standard comprises Z data as well. It is only now possible to define shapes that have inside cuts, by allowing more than one radius at a given angle, and by allowing a series of angles that do not invariably increase (that's in version 3.09 of the standard, which is about to be released).

    Notches and rectangles in the edge have long been handled as drill features.
    I recently read over the standard and your post was interesting. In the TRCFMT= spelling may be wrong but their is a new U designation for the unequal angles as you mentioned. Turns out VW does not accept these trace files. Interestingly enough my particular setup uses the U instead of the E for equiangular even though the angle data A= is equally spaced apart. I created a filter which changes the 4 places in my files that this U appears and now VW accepts my traces.

    I talked to your son at VEE about this as well as another vision web issue and suggested maybe a particular filter to export for vision web. I also spoke to the vision web people to see if they could incorporate the newest standard or at least fail a bit more elegantly then just not accepting a job. I understand that if a particular piece of equipment doesn't understand a new item in the standard then its supposed to ignore it, but the TRCFMT record set has existed from the initial standard from my understanding so a change in this record set should be a priority to any vendor to recognize.

    I wish VW would get with the times.

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    Objection! OptiBoard Gold Supporter shanbaum's Avatar
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    The "U" mode has always been there, but it has been used only rarely. The new mode of which I wrote is "C", which is like "U" but allows the angle values to decrease as well as increase, making "inside cuts" possible. So far as I know, no machine vendor has implemented that yet. It's very odd to use the "U" mode with equally-spaced angles; that's just wasting space.

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    Master OptiBoarder MakeOptics's Avatar
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    Quote Originally Posted by shanbaum View Post
    The "U" mode has always been there, but it has been used only rarely. The new mode of which I wrote is "C", which is like "U" but allows the angle values to decrease as well as increase, making "inside cuts" possible. So far as I know, no machine vendor has implemented that yet. It's very odd to use the "U" mode with equally-spaced angles; that's just wasting space.
    That's my thought exactly, the additional angle data is redundant if the angles are equally spaced. Still not a big deal with the negligible file sizes required for an average trace, but the fact that the particular vendors equipment I am using uses a version of a protocol that has not widely been implemented yet even through their own portal just seems poorly thought out. Plus the VCAs protocol allows for many ways for equipment to gracefully fail in many cases to accommodate changes to the protocol as well as experimental record sets, I would think that a web portal that transmits these files to a lab could implement some of these fail safes in their software.

    Thank you Robert for your response, it further helps me understand and confirm where the problem truly rears its ugly head.

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