🔒 Locked

Convert formula

Started by ProblemBaby Nov 16, 2004 at 4:18 PM 4 replies 950+ views

Original Post

Nov 16, 2004 at 4:18 PM

Hi Ive some code that looks like this it is collision code for balls: // x, y = length between centers // xv0, xv0, yv1, yv1 = velocity vectors for ball0 and ball1 length = BIOS_Sqrt(x*x+y*y); normal_x = x / length; normal_y = y / length; a = DotProduct(normal_x, normal_y, xDiff, yDiff); xn = normal_x * a; yn = normal_y * a; xv0 += xn; yv0 += yn; xv1 -= xn; yv1 -= yn; Its works amazing but I want to do it with polar coordinates angle and length intead of x, y for the speed. Is it possible to do?? or do Ive to convert first to x,y and then back to angle,length? If it is possible please give me a hint on how to do it Thanks in advance

JohnBolton

132

JohnBolton

Nov 17, 2004 at 2:39 AM

I don't think there is a faster or easier way to do it than to convert to x/y, add them, and then convert back.

LilBudyWizer

145

LilBudyWizer

Nov 17, 2004 at 4:15 AM

The dot product for two polar vectors (r1,t1) and (r2,t2) is |r1||r2|cos(t1-t2).

ProblemBaby

Author

ProblemBaby

Nov 17, 2004 at 5:27 PM

xn = normal_x * a;
yn = normal_y * a;

xv0 += xn;
yv0 += yn;
xv1 -= xn;
yv1 -= yn;

isnt this possible to do much simplier with polar coordinates??

I know it cant be
vel0 += a;
vel1 -= a;

But I cant either find out how to do it!
Isnt it possible

LilBudWizer: Thanks, that took me one step closer

ProblemBaby

Author

ProblemBaby

Nov 17, 2004 at 5:30 PM

Then I also wonder if it is possible to find out the length of a side in a triangle if I know the two other lengths and the angle between them.
I know I can use sqrt and dont need the angle

but isnt it somehow possible to do it witout sqrt and use the angle instead in some way?

SuperNerd

Nov 17, 2004 at 6:11 PM

Try using Sin and Cos to change the position of the ball or whatever is moving
x += Sin(angle)*length;
y += Cos(angle)*length;

if you need to find the angle it's pretty easy with Atan2

angle = Atan2(point1y-point2y,point1x-point2x);

I tried to make the variables self explanitory;

Topic Locked

This topic has been locked by a moderator. New replies are not allowed.