Black mark?

oskar

Hi, I've made a program where a truck moves back and forth. But when the truck moves the background where it has been turns black. I just wonder if it's my computer or if I need to change the code.

int rect1pos = 20; int rect2pos = 80; int rect3pos = 80; int ell1pos = 30; int ell2pos = 40; int ell3pos = 95; int step = 1;

void setup(){ size(300,300); background(255);

} void draw(){ line(0,150,300,150); fill(255,0,0); rect(rect1pos,105,60,40); fill(255,0,0); rect(rect2pos,125,25,20); fill(255,0,0); rect(rect3pos,115,15,10); fill(0); ellipse(ell1pos,145,10,10); fill(0); ellipse(ell2pos,145,10,10); fill(0); ellipse(ell3pos,145,10,10); rect1pos = rect1pos+step; rect2pos = rect2pos+step; rect3pos = rect3pos+step; ell1pos = ell1pos+step; ell2pos = ell2pos+step; ell3pos = ell3pos+step; if(rect2pos > 275){ step = -1;

}

if(rect1pos < 0){ step = 1; } }

quark

The draw method is executed about 60 frames per second so what is happening is that the black mark is a previous drawing of the truck. You need to clear the display at the start of the draw method

void draw(){ background(255); // white background

followed by the rest of your draw code.

oskar

Thanks!