[android-developers] Re: Game math/logic calulating movement

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 <jeffisagen...@gmail.com> 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 <jeffisagen...@gmail.com> 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 <rbgrn....@gmail.com> 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 <jeffisagen...@gmail.com> 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 android-developers@googlegroups.com
To unsubscribe from this group, send email to
android-developers+unsubscribe@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/android-developers?hl=en