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direction vector

Started by AGD011 Sep 4, 2003 at 1:31 PM 3 replies 600+ views

Original Post

Sep 4, 2003 at 1:31 PM

ok, I''ve read a number of articles regarding this question yet for some reason I''m still missing something. I am trying to get a basic direction vector....this should be easy because I''m on a flat surface (not looking up or down, and no tilting left/right). according to the axis I''m working with (X,Y,Z)..the X axis rotate''s the view angle left/right. I have two points: position[3] and direction[3]. from what I''ve read, this should be as easy as saying rotation[0]=(direction[0]-position[0]). ([0]=x, [1]=y etc.) why is this not working...what am I missing? thankyou in advance for all help. I know this topic has been talked about before, but the previous articles are not turning on any lightbulbs...

Nypyren

1,001

Nypyren

Sep 4, 2003 at 3:11 PM

Uhm... whoa.

Direction vectors are usually not thought of as positions.

If you have two points in space, A and B, you can find the offset vector from A to B by saying D = A-B (which expands to D.x = B.x-A.x, D.y=B.y-A.y) and then if you want the direction, it's as simple as adjusting the offset vector to a length of 1. (You can force a vector to length 1 by dividing both X and Y by the vector's original length)

However, I must ask this: WHAT are you trying to do again?

I shall rewrite your original example code:


offset = look_at - direction;
direction = offset / offset.GetLength();
distance = offset.GetLength();

Assuming that those variables are instances of a class that overloads the - and / operators and defines a GetLength function.

[edited by - Nypyren on September 4, 2003 4:28:15 PM]

AGD011

Author

AGD011

Sep 4, 2003 at 4:21 PM

thank you for your response...sorry if I was unclear in the first post.

ok, imagine that you are in a paint program and you draw a line. the first time you click your mouse is where the line begins (point1), the place where you release the mouse is where the line ends (point2). I am trying to make point1 the position. (the camera will appear here ), I want to make point2 the direction the camera is looking.

does that make more sense? am I going about this the wrong way?

Sep 5, 2003 at 4:08 AM

Use gluLookAt( p1.x, p1.y, p1.z, p2.x - p1.x, p2.y - p1.y, p2.z - p1.z, 1.0f, 0.0f, 0.0f ) Maybe you should invert last 3 values. Nothing else to do !

uber_n00b

Sep 5, 2003 at 1:42 PM

I agree. look up more on gluLookAt (I was going to post that last night but gamedev decided to not load my response =\)

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