java - Test if point is within line range on 2D space -


this question bit hard formulate i'll start showing image:

enter image description here

i want test if points (such p1 , p2 on image) within dotted lines perpendicular line @ limits. know coordinates of points test , line's limits.

so p1 false, , p2 true.

what computationaly efficient way calculate this?

i'm working floats in java.

this can efficiently done dot product:

enter image description here

this positive if a has component parallel b, , negative if anti-parallel.

therefore if have line segment defined points a , b, , test point p, need 2 dot product operations test:

dot(a - b, p - b) >= 0 && dot(b - a, p - a) >= 0

edit: graphical explanation:

enter image description here

the dot product can shown be:

enter image description here

thus if θ > 90 dot(a, b) < 0, , vice versa. problem:

enter image description here

in case 1, when dot(a - b, p - b) > 0 p on correct side of dotted line @ b, , vice versa in case 2. symmetry can same operation @ a, swapping a , b.


Comments

Post a Comment

Popular posts from this blog

ubuntu - PHP script to find files of certain extensions in a directory, returns populated array when run in browser, but empty array when run from terminal -

i running os ububtu 16.04. ultimate goal able run php script cron job every minute. here php script located @ /var/www/html/tests/test/index.php : <?php $directorypath = $_server['document_root']."/tests/test/data/"; echo "directorypath: $directorypath<br><br>";//check $imagefilepathsarray = glob($directorypath . "*.{png,gif}", glob_brace); echo "<br><br>imagefilepathsarray: "; print_r($imagefilepathsarray);//check ?> when open php script in browser visiting url my-ip-address/tests/test/index.php , get: directorypath: /var/www/html/tests/test/data/ imagefilepathsarray:array( [0] => /var/www/html/tests/test/data/pic.png [1] => /var/www/html/tests/test/data/pic.gif ) before writing cron job in crontab file, need check if can run anywhere using terminal . opened ubuntu terminal @ /home/ location, , executed in terminal: sudo php /var/www/html/tests/test/index.php i got following out...
Read more

php - How can i create a user dashboard -

today have questions you, want create user dashboard site, include (obviously), users data, example -email -username -and others stuff how can information, , print them in html page? if can, how can these information via php sessions? shuld use session? example, if user login, , start new session ( session_start() ), how can data print in dashboard? should use php "project"? in advice, have day , thank time!
Read more

javascript - How to detect toggling of the fullscreen-toolbar in jQuery Mobile? -

i have jquery mobile page fixed full-screen toolbar, data-tap-toggle enabled. straight under toolbar have positioned banner should slide upwards when toolbar hiding , slide downward when toolbar showing. jquery mobile toggles toolbar applying , removing ui-fixed-hidden class - sadly, can't find in documentation of toolbar widget toggle , hide or show event that. how can detect when toolbar toggled, reposition banner? .banner { position: fixed; background-color: darkseagreen; top: 46px; min-height: 48px; width: 100%; text-align: center; line-height: 48px; } <!doctype html> <html> <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width, initial-scale=1, user-scalable=no"> <link rel="stylesheet" href="https://code.jquery.com/mobile/1.4.5/jquery.mobile-1.4.5.css"> <script src="https://code.jquery.com/jquery-1....
Read more