How to get an object's direction of travel?

[Scott Ayers]

I learned a bit more about using vectors to move and rotate objects.
But I'm still stuck on getting, and using, a directional vector to change it's direction of travel.

Here's what I have so far.
I can move the cube fine using vectors. But I'm stuck on reversing it's direction of travel: main(doc,op)
{
var obj = doc->FindObject("Cube");
var pos = obj->GetMg()->GetV0();// get it's Global position
var V = vector(0,0,0); // Create a vector to use for measuring distance traveled
var speed = 15;
var direction = Degree(360);// the initial direction of travel that will be reversed later on
var ReverseDirection;

V.y = pos.y + speed * cos(direction);

if (V.y > 100) // If the cube has reached this limit
{
V.y = 100; // force the object to not exceed 100
ReverseDirection = (3*PI) - direction; // Set the new direction
}

else if (V.y < -100) // If the cube has reached this limit
{
V.y = -100; // force the object to not exceed 100
ReverseDirection = (3*PI) - direction; // Revese the cube's direction
}

obj ->SetPosition(V); // Apply the positions
}

Anyone have any ideas?

-ScottA

[tcastudios]

For calculating direction I usually store the previous position
or animate the object/document forward (to get next position)

Cheers
Lennart

[Scott Ayers]

Do I need to make use of the time function to get the second to last frame. Then record the object's position somehow? Or is it done some other way?

I've been using Google to research how to do this. And I've seen that method of storing the object's previous position mentioned many times. But they never show how they actually go about recording it.
They always seem to skim over that part. So I thought I'd try and use trig(Cos) instead.
I'm finding tons of theory out there. But little in the way of practical examples.

-ScottA

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