View Full Version : [SOLVED] chasing people in video games

May 8th, 2011, 03:36 AM
Hello all,

I had a quick question about vector algebra etc. My game isn't working so well.

I have this game and the "bad guys" are supposed to be chasing me. I've done this before in C/C++ but its not working so well in Scheme...I'll just write it in Cish syntax.

Anyway the algorithm goes like this:

vector_direction = vector_normalize(
vector_distance( player, sprite )) ;

nextpos += (direction * velocity ) ;

sprite.goto( nextpos )

is there something I am not taking into account here? My sprites are going everywhere! Thank you ahead of time for your help.

Tony Flury
May 8th, 2011, 09:17 AM
what does Vector Normalize do ?

You appear to be basing the Direction on just a distance..

Don't you want to calculate the vector between you and the bad guy, and move along that vector ?

May 8th, 2011, 12:49 PM
I assume vector_normalize normalizes the vector to a length of 1.
Then, like Tony Flury said you should do something like this:

vector_direction = vector_normalize(player - sprite);

nextpos += (direction * velocity);


May 8th, 2011, 04:26 PM
Yes sorry vector_normalize takes a vector and turns it into a unit vector or direction vector. I give it the player - sprite vector to normalize. I think I almost figured it out. I swapped the two in another function. Dumb me. Thank you for all of your help.

Just a few more questions. They chase me first and then they start to back up until they align with me, then stop. Do I have to take into account positive or negative values if the center of my world is (0 , 0 , 0 ) or should that not matter? I can just change my world position if anything.

Thank you again!