On 05/24/2011 12:16 AM, Bruce Bruen wrote: > On 24/05/11 13:14, 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. >> >> > 1) Need to include i being the time increment in the same units as velocity > 2) Basic physics says point will move d units in i time increments according > to distance=velocity * time . So point will have a deltaXY of v*i. > Basic trig converts this to deltaX and deltaY using the old "Sign On > Here 'Coz Alf Has Tan OverAlls" > deltaX = deltaXY * sin(a) > deltaY=deltaXY *cos(a) > > Bobs, yer uncle, return deltaX and deltaY!
Very true. I didn't want to include time because I didn't want to complicate the issue. Time is basically whatever number I multiply the velocity by in the mystical and unknown equation. In my case time is a single rendering frame, so it's not currently tied to any real sense of the word "time". While I appreciate the hint, what's the equation for DeltaX/Y using Sin/Cos/Tan if that is what's being used? I think you may be a bit more under the weather than I. :) And it's not even Friday... Fortunately when I cross the threshold I stop programming and write music for the game. A much more forgiving medium for sure. -- Kevin Fishburne Eight Virtues www: http://sales.eightvirtues.com e-mail: sa...@eightvirtues.com phone: (770) 853-6271 ------------------------------------------------------------------------------ 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
