Sherman,
I don't know the answer to the 2nd question, but as to 'what should trigger the fade-in, fade-out?': in addition to altitude, you may want to consider using the 'is the camera close-enough to being right overhead?' criteria. You can answer this question by doing a dot product of the camera and city position vectors w.r.t. center of Earth. Normalize the position vectors to get unit vectors, then x = v1.dot(v2), then if x == 1, camera is right over, if x == 0, camera is 'perpendicular' (i.e. right on the horizon for observer on a city roof if far enough away (like a star)). So maybe x = 0.9 is a reasonable threshold. -Yegor _____ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of sherman wilcox Sent: Saturday, January 27, 2007 4:27 PM To: osg users Subject: [osg-users] text on an ellipsoid model I have an OSG app that can display city names @ a given lat/lon on an ellipsoid model of the earth created with osgdem. I want to extend this a bit in two ways. First, I want to control when a given city pops up into view. Second I want to fade the text in when that threshold has been reached. First question: How do I trigger text to show or hide? I've considered using the camera altitude above the earth as the reference point and fade a given city name in when the camera reaches this altitude. Sound reasonable? Second question: How do I fade the text in? Do I use a node callback?
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