Then we draw the ball using a red color and a 4 pixel wide pen. We draw an ellipse with the given boundary box. First the bottom left coordinate of the bounding rectangle is given. Be aware, the computer screens have the zero position at the top left corner, not as most people would expect at the bottom left corner. Therefore, we need to calculate the y-positions by some negative signs. Retrieved from "https://techbase.kde.org/index.php?title=Translations:Development/Tutorials/Physical_Simulation/91/en&oldid=102973" This page was last edited on 19 July 2019, at 17:43. Content is available under Creative Commons License SA 4.0 unless otherwise noted.