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Placemark or model disappearing when eye is well above it.

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  • Placemark or model disappearing when eye is well above it.

    I saw something odd when using collada models on web WW and confirmed that I also see it with regular placemarks. Not sure if I am missing something like a visibility distance or something.

    If I create a placemark at an absolute altitude of 10,000m and view directly above it and zoom in. When the eye is around 35k the placemark disappears.

    Is there a reason I cannot see the placemark all the way down to eye level of 10,001 meters?

    I used the CustomPlacemark example and set the altitude to 10,000 to replicate / test it.

    Thanks for any advice.


  • #2
    I tracked this down to the NavigatorState projectWithDepth function. Comments suggest the point is being clipped against the near and far clip planes. If I comment out the return in that check, then I can zoom all the way down to my placemark without it being clipped.

    Honestly, I dont understand this well enough to know how the z value is being calculated. If anyone can suggest a way in settings to prevent this from being clipped or control it via config somewhere... I'd appreciate it.

    // Complete the conversion from model coordinates to clip coordinates by dividing by W. The resultant X, Y
    // and Z coordinates are in the range [-1,1].
    x /= w;
    y /= w;
    z /= w;
    // Clip the point against the near and far clip planes.
    if (z < -1 || z > 1) {
      return false;  //  commented out this line to allow placemark to be visible at any altitude.
    I added some snapshots of what I'm seeing in case my description is not clear.