hmmm.. it seems to me that all the trig functions (sin/cos etc) are unnecessary.
The screen is just a 2D grid, so the difference in position between one point and another is always just a difference of x/y values. If I were you, I would just determine the difference in x and y between your start and end positions, then move through a portion of each with every step based on your speed. For example: If your current position is 50,50, and you want to move to 100,200 in 1 second, then you just work out the diff, and determine how much to move each millisecond: diff is 50 on the x axis (100 - 50) and 150 on the y axis (200-50) so each millisecond, move X by 50/1000 and Y by 150/1000. Then if your frame takes 16ms to render (hence the move step is 16ms), then you would be moving X by (16 x 50/1000) and Y by (16 x 150/1000) (using floats of course.. not ints). The advantage here is much simpler calcs (== better performance) and you don't care about whether your left/right/up/down because the +ve/- ve results from the simple arithmetic will handle it. This assumes you are only moving in 2D of course. On Aug 29, 9:12 am, Jeffrey <[email protected]> wrote: > Okay, figured it out. I had some remnants from an old system still in > there and was referencing a variable that wasn't being updated > correctly. > > Thank you for you help :) > > On Aug 28, 5:47 pm, Jeffrey <[email protected]> wrote: > > > > > The problem is that it is only moving the image one direction along > > the slope of the line. I've tried making a condition that checks to > > see if the target area is to the left of the current position, and if > > so then make the X/Y differences negative, but that works very > > sporadically, and make the image move in crazy ways sometime. > > > On Aug 28, 5:33 pm, Jeffrey <[email protected]> wrote: > > > > This almost works, but when I click on a point that has a smaller X > > > value than it's current position it reverses the Y Direction. > > > > On Aug 27, 1:01 pm, Robert Green <[email protected]> wrote: > > > > > Direction will be in the range -180 to 180 so don't use abs! Always > > > > use sin/cos for y/x respectively when in y+ down 2D coordinate > > > > systems, otherwise x/y respectively. > > > > > Here is kind of what you want > > > > > // tickDelta should be something like .016f to .033f - definitely > > > > should total 1.0f per second :) > > > > float tickDelta = (currentMs - lastMs) / 1000f; > > > > // now mMoveSpeed can be expressed in units-per-second and it'll work > > > > at any framerate if you multiply by tickdelta > > > > > float touchDelta = (float)(TouchY - V.CurY) / (TouchX - V.CurX); > > > > float dirRads = (float)Math.atan(touchDelta); > > > > float amountX = (float)Math.cos(dirRads) * mMoveSpeed * tickDelta; > > > > float amountY = (float)Math.sin(dirRads) * mMoveSpeed * tickDelta; > > > > x += amountX; > > > > y += amountY; > > > > > // no additional checks needed. This is how you do 2D directional > > > > movement. > > > > // this assumes that either TouchX/TouchY or V is set only when the > > > > touch is touched down initially so that a vector is made when the > > > > touch moves and that value is not updated. > > > > > On Aug 26, 8:40 pm, Jeffrey <[email protected]> wrote: > > > > > > I know this is more of a general programming question, but my Android > > > > > friends here have always been helpful. I am trying to make an image > > > > > move from one part of the screen to a position the user touches, as a > > > > > constant speed. I don't know the best way to go about doing this and > > > > > the way I have been trying to get to work is taxing my brain too much. > > > > > > I have been using geometry to calculate slope, then using Sin * > > > > > movement speed to calculate the difference in X,Y coordinates. > > > > > > This is the code I'm looking at: > > > > > > TouchX = V.TX; (This is the touch event > > > > > coordinates > > > > > TouchY = > > > > > V.TY; ) > > > > > > Slope = (TouchY - V.CurY) / (TouchX - > > > > > V.CurX); (this figures out > > > > > the slope of the line to the touch point) > > > > > DegreeSlopeY = Math.atan(Slope); > > > > > DegreeSlopeY = Math.abs(DegreeSlopeY); > > > > > (this is so > > > > > that I can calculate the direction the image should travel along the > > > > > slope) > > > > > DegreeSlopeX = (90.0000000000000 - > > > > > DegreeSlopeY); > > > > > NewY = (mMoveSpeed * Math.sin(DegreeSlopeY)); > > > > > (This calculates the > > > > > shift in Y axis for the image) > > > > > NewX = (mMoveSpeed * Math.sin(DegreeSlopeX)); > > > > > (This calculates the > > > > > shift in X axis for the image) > > > > > if(TouchX < V.CenterX) NewX = -NewX; (This > > > > > is to finish > > > > > calculating the correct X axis direction to travel) > > > > > if(TouchY < V.CenterY) NewY = -NewY; (This > > > > > is to finish > > > > > calculating the correct X axis direction to travel) > > > > > > The problem that I'm having is the image is veering way of course when > > > > > traveling in Y heavy paths. When traveling horizontally it works > > > > > almost perfect. > > > > > > I know there is probably an easier way though I don't know how to use > > > > > a lot of things (like OpenGLES) so if your advice is to use a > > > > > different method please link a tutorial for that method if you know of > > > > > one. > > > > > > Thanks in advance. -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
