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3D orientation script
Hey fellow script-heads,
I’m trying to animate “tracer” bullets between two 3D points and I want to be able to orient the bullet along the path. I can’t use “orient to path” cause there is no path as such – the positional motion is an expression too. I’m therefore trying to do the orientation trig based on the start and end points, but I can’t seem to find anything on the net to help me maths-wise. I’ve tried doing the orientation as 2 separate 2d x/z and x/y calculations but that’s not right. Anyone know the trig for the 3D angles between two 3D points?
Cheers!
sCam
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2 Replies
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Just curious, what’s the Positional expression?
Can you modify Dan’s auto-orient expression, here:
https://www.motionscript.com/design-guide/auto-orient-y-only.html
It uses toWorld between two points. Maybe an altternative to “Math.atan2” or subtract 90 degrees from something???
Also, t-would be a pain, but you could always take that Positional expression and Animation>Keyframe Assistant>Convert Expression to Keyframes, then use “orient to path”. Bad idea I know, sooo many keyframes and expressions are so clean.
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Heya – thanks for that link! Yes that’s kind of what I’m doing. That script orientates an object to “look at” another object but in the y-axis only. I’m trying to do it for both the y-axis (left to right) and also the x-axis (up down). I haven’t actually cracked it yet, but having researched it a bit more I think this would be the principle:
1. Calculate y-axis rotation by “looking down” on the vector from above in 2d, and doing a basic atan2 on the x and z distances (as per Dan’s example above).
2. Now here’s the trick – rotate the vector negatively by the result in the y-axis, so you effectively ‘remove’ this rotation from it.
3. Now you’re free to do the same for the x-axis rotation as you’ve ‘straightened’ the vector up to run flat along the z axis.
That’s the theory anyway, bear in mind I might be totally wrong!. I think it would definitely have its limitations too. I ran out of time on this one to finish it off properly and so did it by hand in the end. If I get round to trying it out I’ll post the results.
Cheers, sCam
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