next »

[omgnoseat]

I've seen this on a different forum, and it has been icredibly helpful, and probably prevents a lot of unnecessary topics.

So ask all your small questions that don't diserve it's own topic here.

Example

Question

How do I invert a boolean?

Anwser

boolean = !boolean

[omgnoseat]

Now for my own question;

I have a vehicle class that a Vector3 velocity. How could I figure out the velocity in it's forward direction? (forward as in front of the vehicle's rotation)

[_e_va]

dum this is a trick to mak me do math

[Polly]

I have a vehicle class that a Vector3 velocity. How could I figure out the velocity in it's forward direction? (forward as in front of the vehicle's rotation)

Create a matrix from your rotation, multiply the vector with the matrix, get the axis that represents the forward direction.

[nikki]

good idea for thread!

[omgnoseat]

I have a vehicle class that a Vector3 velocity. How could I figure out the velocity in it's forward direction? (forward as in front of the vehicle's rotation)

Create a matrix from your rotation, multiply the vector with the matrix, get the axis that represents the forward direction.

Fortunately I already have the matrix. That does sound very logical, but unfortunately this does not seem to return any logical values.

Code:

car.transform.transformVector(car.velocity).z; //actionscript3 matrix/vector3D classes

EDIT: seemed like I needed to invert the matrix first, not sure why, but it does the trick!

[Pishtaco]

Now for my own question;

I have a vehicle class that a Vector3 velocity. How could I figure out the velocity in it's forward direction? (forward as in front of the vehicle's rotation)

Dot product with a unit vector in the forward direction.

[Polly]

seemed like I needed to invert the matrix first, not sure why, but it does the trick!

If you already have a rotation / transformation matrix for whatever reason, use the dot product solution as proposed by Pishtaco ( get the unit vector from that matrix ). Inverting a matrix is slow ( depending on your rotation representation creating the correct matrix directly could be allot faster though ).

[ham and brie]

Inverting the matrix omgnoseat has would make sense if it is the rotation from local space of the vehicle to world space.

The inverse of a rotation matrix is the transpose, so it's pretty easy to get values out needed for the dot product either way.

[eddietree]

dot product, yo