Drawing rectangle between two points with arbitrary width

Question

I\'m trying to draw a line between two (2D) points when the user swipes their finger across a touch screen. To do this, I plan on drawing a rectangle on every touch update b

Answer 1

Easy way (I'll call the "width" the thickness of the line):

We need to calculate 2 values, the shift on the x axis and the shift on the y axis for each of the 4 corners. Which is easy enough.

The dimensions of the line are:

width = x2 - x1

height = y2 - y1

Now the x shift (let's call it xS):

xS = (thickness * height / length of line) / 2

yS = (thickness * width / length of line) / 2

To find the length of the line, use Pythagoras's theorem:

length = square_root(width * width + height * height)

Now you have the x shift and y shift.

First coordinate is: (x1 - xS, y1 + yS)

Second: (x1 + xS, y1 - yS)

Third: (x2 + xS, y2 - yS)

Fourth: (x2 - xS, y2 + yS)

And there you go! (Those coordinates are drawn counterclockwise, the default for OpenGL)