• # Fast 2D Line Intersection Algorithm

Math and Physics

Perhaps something like this may help. Though it may not be fast enough

void Intersect_Lines(float x0,float y0,float x1,float y1, float x2,float y2,float x3,float y3, float *xi,float *yi) { // this function computes the intersection of the sent lines // and returns the intersection point, note that the function assumes // the lines intersect. the function can handle vertical as well // as horizontal lines. note the function isn't very clever, it simply //applies the math, but we don't need speed since this is a //pre-processing step float a1,b1,c1, // constants of linear equations a2,b2,c2, det_inv, // the inverse of the determinant of the coefficient matrix m1,m2; // the slopes of each line // compute slopes, note the cludge for infinity, however, this will // be close enough if ((x1-x0)!=0) m1 = (y1-y0)/(x1-x0); else m1 = (float)1e+10; // close enough to infinity if ((x3-x2)!=0) m2 = (y3-y2)/(x3-x2); else m2 = (float)1e+10; // close enough to infinity // compute constants a1 = m1; a2 = m2; b1 = -1; b2 = -1; c1 = (y0-m1*x0); c2 = (y2-m2*x2); // compute the inverse of the determinate det_inv = 1/(a1*b2 - a2*b1); // use Kramers rule to compute xi and yi *xi=((b1*c2 - b2*c1)*det_inv); *yi=((a2*c1 - a1*c2)*det_inv); } // end Intersect_Lines
Scott

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## User Feedback

Fantastic for people who needs those "long projectiles" like fast bullets.
Missing only the line versus rectangle collision!

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