problem with maths :S

Replies(2)

cedrickie..

Re: problem with maths :S

3 years ago

there is an intersection example by case, maybe this answers your question.

floatax = 50;   // 1st point x
                
                   float ay = 50;   // 1st point y
                  
                   float bx = 200;  // 2nd point x
                  
                   float by = 300;  // 2nd point y
                  
                   float cx = 350;  // 3rd point x
                  
                   float cy = 80;   // 3rd point y
                  
                   float dx;        // 4th point x
                  
                   float dy;        // 4th point y
                  
                   void setup() {
                  
                     size(400, 400); 
                  
                     ellipseMode(RADIUS);
                  
                     smooth();
                  
                   }
                  
                   void draw() {
                  
                     background(204);
                  
                     dx = mouseX;
                  
                     dy = mouseY;
                  
                     if (lineLineIntersect(ax, ay, bx, by, cx, cy, dx, dy) == true) {
                  
                       stroke(255); 
                  
                     } else {
                  
                       stroke(0); 
                  
                     }
                  
                     line(ax, ay, bx, by);
                  
                     line(cx, cy, dx, dy);
                  
                   }
                  
                   boolean lineLineIntersect(float x1, float y1, float x2, float y2, float x3, float y3, float x4, float y4 ) {
                  
                     boolean over = false;
                  
                     float a1 = y2 - y1;
                  
                     float b1 = x1 - x2;
                  
                     float c1 = a1*x1 + b1*y1;
                  
                     float a2 = y4 - y3;
                  
                     float b2 = x3 - x4;
                  
                     float c2 = a2*x3 + b2*y3;
                  
                     float det = a1*b2 - a2*b1;
                  
                     if(det == 0){
                  
                       // Lines are parallel
                  
                     } 
                  
                     else {
                  
                       float x = (b2*c1 - b1*c2)/det;
                  
                       float y = (a1*c2 - a2*c1)/det;
                  
                       if(x > min(x1, x2) && x < max(x1, x2) && 
                  
                          x > min(x3, x4) && x < max(x3, x4) &&
                  
                          y > min(y1, y2) && y < max(y1, y2) &&
                  
                          y > min(y3, y4) && y < max(y3, y4)){
                  
                         over = true; 
                  
                       }
                  
                     }
                  
                     return over;
                  
}

bluurryy

Re: Re: problem with maths :S

3 years ago

so this is just in two dimension. I'd like it in 3. so I think the problem is quite different? or am I wrong?

I can't just calculate the "det" in your program...

or can I?

Replies(2)

Re: problem with maths :S

Re: Re: problem with maths :S

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