On Tuesday, May 24, 2011 05:44:14 Kevin Fishburne wrote: > I was already helped graciously in figuring out how to translate a point > in a plane along its local axes at a given orientation, but now need a > bit of the inverse of the equation. > > I need to know the (x, y) offset of a point at a given orientation and > velocity. For example if a point is moving at an angle of 45 degrees (or > radians, take your pick), what would its x and y coordinate be > increased/decreased by? The variables I can think of would be: > > x1 (point's current x coordinate) > y1 (point's current y coordinate) > a (point's angle/orientation in degrees/radians) > v (point's velocity) > x2 (x coordinate offset of point's new position) > y2 (y coordinate offset of point's new position) > > The calculation would take x1, y1 a and v as inputs and produce x2 and > y2 as offsets (x1 + x2, y1 + y2 = point's new position). > > There really should be a list of basic things like this for graphics > programmers. I've searched for years and found practically nothing. > Weird, considering this has probably been done thousands of times since > the days of DOS. :/ > > In case anyone's wondering why I need this, the equation will allow > particles and projectiles to follow logical paths. Currently they're > bound to local coordinates and ignore player orientation. Digging, > shooting arrows, throwing objects, etc. can't work without it.
Hello Kevin, the problem seems pretty easy to solve, so I'm not sue i understand the question correctly. A good idea would be to use polar coordinates for this: P( r, a) where r = radial distance to (0,0) offset and a the angle a . r = sqrt( x^2 + y^2) r(p2) = r(p1) + vt , new radius point 2 = 1st radius + distance to move (velocity * time) a does not change in cartesian coordinates: x2 = x1 + cos(a) * v * t y2 = y1 + sin(a) * v * t if you need more complex paths, using matrices is a good way. but always time is needed to calculate. You did not mention time t so i assume i did not understand the question. wally ------------------------------------------------------------------------------ vRanger cuts backup time in half-while increasing security. With the market-leading solution for virtual backup and recovery, you get blazing-fast, flexible, and affordable data protection. Download your free trial now. http://p.sf.net/sfu/quest-d2dcopy1 _______________________________________________ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
