Visualizing DataProgramming meets Graphic Design at ITP

Ok, first off, here is my issue:

1) I have two distinct points on a globe and i want to draw a line between them at a nice arc.

From what I understand there are two solutions:

a) calculate the x, y, z of those boxes and then draw an arc between them.  This turns out to be incredibly difficult, but using screenX, screenY, and screenZ is a start.

You use the mid point equation:

xMid = (x1 + x2)/2
yMid = (y1 + y2)/2
zMid = (z1 + z2)/2

and *snoooooorreeee*

f*ck math, who cares…

2) My way, abstractly, check code for exact solution, is to calculate the midpoint of the long, lat coordinates and recursively plot points over and over till you have a line.  Here is the meat of that:

float lat1 = radians( -34 ); float lon1 = 151; // sydney
float lat2 = radians( 37 ); float lon2 = 127; // seol

float dLon = radians( lon2 - lon1 );

float Bx = cos( lat2 ) * cos( dLon );
float By = cos( lat2 ) * sin( dLon );

float lat3 =  atan2( sin( lat1 ) + sin( lat2 ),
                   sqrt( ( cos( lat1 ) + Bx ) *
                   ( cos( lat1 ) + Bx ) + By * By ) );

float lon3 = radians( lon1 ) + atan2( By, cos( lat1 ) + Bx );

At this point you essentially done. Just rotate twice and translate once and draw the f*cking box or point or whatever.

To finish off the line just do this over and over again recalculating the midpoint. You might calculate the number of times to recurse based on the distance which is calculated:

float dLon = radians( lon2 - lon1 );

Animate it? No f*cking problem. Just store longs and lats as you go and animate the drawing of the boxes!

– chris allick

A few classes ago I mentioned this alrogirthm as an alternative method for drawing a circle. It’s very interesting and very very fast.

http://en.wikipedia.org/wiki/Midpoint_circle_algorithm

– chris allick

We haven’t talked much about textures, but you may find this technique useful for your presentation. Here’s Processing’s guide to Textures. Note also that you can load PNGs with transparency as textures, allowing you to do some pretty interesting stuff.

For convenience here’s a roundup of the sample code we’ve passed around so far this semester. If I’ve missed something just add a link in the comments.

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