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# moving a 3d object vector from one place to another by a angle and speed

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Hi all, I am trying to understand how to move a object from one place in 3D space to another 3D point in 3D space by only supplying the angle and speed to move at. The basics I have is to have a vector3D which has x,y,z cords (floats). and from this website, I think that to find out one 3D angle from another would float angleDifference(vector3D other) { double dot1Horizontal = other.x * this->x + other.z * this->z; double dot2Horizontal = other.x * other.x + other.z * other.z; double dot3Horizontal = this->x * this->x + this->z * this->z; double angleCosHorizontal = dot1Horizontal / (sqrt(dot2Horizontal) * sqrt(dot3Horizontal)); return acos(angleCosHorizontal) * (180 / PI); } Vector3D pointA {-1,-1,0}; Vector3D pointB {-1, 1,2} ; printf("angel %f\n", pointB.angleDifference(pointA)); = 63.43... but now how do you convert that angle to move a object in 3D space ?

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Is this a 'true' 3-d problem, or is it really a 2-d problem that happens to take place in 3-d space? (Specifically in the xz plane...) I ask because the code sample you posted appears to compute the angle between two vectors as projected onto the xz plane; in other words, there's really no '3-d' involved there.

Also, a direction in 3-d space cannot be fully specified with only a single angle (additional information is needed).

If you're just trying to get from point A to point B though, no angles are necessary - you can simply compute the direction vector from A to B as:
(B-A) / |B-A|

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Thanks jyk

I suppose your questions are helping my understand what it is I am trying to do as such.

What the main thing that I am trying to create is a laptop base with a laptop lid opening up, and thus the laptop lid needs to move from the closed position and then to the open position (90 degrees) which is where I thought that I needed the angle to move to. (pivoting on the laptop base back as such)

what does

(B-A) / |B-A|

mean ?

(B-A) /

I get B-A do first, but not sure what |B-A| means ? the | part that is.

so when I want to move from one point to another. I was thinking that if I calculate the arc from the start position and then end position and then move along that arc accordingly to a speed reference. Would that be the way of doing it ?

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Hey Genux,

What you are trying to do is rotate an object (your laptop lid) not move it.

Just wanted to clarify that so that you could get better help / find info better for yourself (:

Basically you need to rotate the lid over time along the x axis from 0 to 90 degrees, using the back of the lid (the part that you want to remain still as the lid opens) as the origin for the rotation.

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Quote:
 Original post by genux...(B-A) / |B-A|...I get B-A do first, but not sure what |B-A| means ? the | part that is...

Norm/Length of a vector

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thanks Anntor for that link to the Normal/Lenght, makes allot more sense now :).

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