In case of the kid and the guards, obj_x contains the X coordinate on a 280 units wide screen (suitable for the Apple II), to be converted by calc_screen_x_coord() later.īut for the sword in someone's hand, obj_x is the X coordinate on a 320 units wide screen, already converted using calc_screen_x_coord(). That's why the code is sensitive to the direction of the sprite.īut I still don't know why Mechner attached an evenodd bit to frames, instead of offsetting those images by one pixel. On the Apple II screen, this would swap orange and blue.

The high contrast of this print makes for striking wall art The prints are 11 x 14 inches. If you mirror a sprite around its left edge (the left edge of its leftmost pixel column), then pixels with an even X coordinate will end up at odd X coordinates and vice versa. This is a piece of fan art for my favorite 'creature' design from Ubisofts Prince of Persia video game series. The code pushes the sprite one unit to the right if either direction=left (0xFF) and evenodd bit=1 or direction=right (0x00) and evenodd bit=0.Īgain, this code was inherited from the Apple II version.

Prince of persia 3d development artwork