Vector Math? How can I determine an AI/Actor's forward velocity - Cog Forum

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Vector Math? How can I determine an AI/Actor's forward velocity

2004-10-02, 7:06 AM #1

El Scorcho

*shudder*

Posts: 437

It sounds simple enough. My first thought was GetThingVel, coupled with VectorY would get me what I wanted. Rbots even used this code for jump determination.

However, It appears after some testing that while that does get the velocity of a thing...it doesn't actually get the velocity relative to the things look vector. Rather, the velocity is just relative to the map coordinates. (which, really, is what it should do. :P)

With the player is cake. You just use GetThingThrust(). But Actors do not have thrust in this manner. All values of the actors thrust return 0 so they aren't useful here.

I'm going to play with it some more...maybe some of the code in force_farsight will provide some direction.

-El Scorcho

"Its dodgeball time!" -Stormy Waters

2004-10-02, 7:18 PM #2

Centrist

TIMELINE! OMG I'm so witty

Posts: 293

I'm assuming that by "forward velocity" you mean "forward speed." It's pretty simple to do, just a little hard to visualize:

First you need to get values for the target's looking vector (lvec), the target's velocity vector (vvec), and the target's speed. So using the player, we'll do:

Code:

player=GetLocalPlayerThing();
lvec=GetThingLVec(player);
vvec=GetThingVel(player);
speed=VectorLen(vvec);

Now that we have the basics, we need the cosine (or dot in this case) of the lvec and vvec (the cosine will show us how far apart the two vectors are looking). We will have to normalize vvec so that it has a length of one because we need only vvec's direction for the cosine operation. Then we'll multiply the speed times the cosine and we have our frontSpeed:

Code:

dot=VectorDot(lvec, VectorNorm(vvec));
frontSpeed=speed * dot;
print("your front speed is: ");
printflex(frontSpeed);

And there you have it.

Historians are the most powerful and dangerous members of any society. They must be watched carefully... They can spoil everything. - Nikita Khrushchev.
Kill one man, and you are a murderer. Kill millions of men, and you are a conqueror. Kill them all, and you are a god. - Jean Rostand.

2004-10-03, 6:24 AM #3