spheretoscreen returns NaN when out of bounds

rebaj83 · June 4, 2012 at 8:09 PM

Hello,

When using the spheretoscreen function with a point outside the screen, the function returns sometimes negative values (whitch is ok with what i wanna do).

In some case it returns NaN value but i don't understand why.

Someone may help on this?

Regards!

sachagriffin · June 4, 2012 at 8:51 PM

You should validate your input first..
ifnot (mouse.x > 0,
ifnot (mouse.y > 0,
screentosphere(mouse.x,mouse.y,toh,tov);
,
trace('invalid input');
);,
trace('invalid input');
);
NaN is short for not a number.

rebaj83 · June 4, 2012 at 10:23 PM

Hey Sacha,

Yes NaN = not a number

in fact i do spheretoscreen on a certain point (long/lat) not on the mouse coordinates (i need the cartesian coordinates of the point)

sometimes the function is fired when that point is "out of screen" : in some cases the function return negative values, which is fine for me but in other cases the function returns NaN

i can't clearly identify why this happens

any idea?

sachagriffin · June 4, 2012 at 11:56 PM

Trace out your input. Your input probably has an exponent in it.

klaus.krpano · June 5, 2012 at 7:26 AM

Hi,

the value 'Not a Number' (NaN) is correct for some values for the spheretoscreen() action,

when the given coordinate is pointing backwards / away from the screen,
then the 'viewing ray' from the viewer will never 'hit' the screen and so a projection on the screen is not possible,

best regards,
Klaus

rebaj83 · June 5, 2012 at 9:02 AM

ok i get it

projection seems to be done on the hemisphere facing the screen right?

klaus.krpano · June 5, 2012 at 10:36 AM

Quote from rebaj83

projection seems to be done on the hemisphere facing the screen right?

yes, it can be also seen this way

spheretoscreen returns NaN when out of bounds

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