Sams Teach Yourself Android Game Programming in 24 Hours

Hour 19. Manipulating Sprites with Matrix Transforms

What You’ll Learn in This Hour

• Using matrix translation

• Using matrix rotation

• Using matrix scaling

• Combining all three transforms into one matrix

• Drawing animation frames with matrix transforms

This hour delves into the awesome subject of matrix transforms, giving us the capability to rotate, scale, and translate a sprite. Although we can already translate (move) and scale a sprite using the known drawBitmap() methods, an additional overload of the method takes a Matrix parameter instead. Because matrix math is much faster than trigonometry (that is, using sine and cosine), and because a matrix can handle all three transforms at once, this is clearly where we want to go with our ...