# Extracting Relative Transforms

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Can we use Extract Transform these days?

Or go back in time and use the Align SOP, which will do exactly what Alvin needs and has been there for more than decade.

Old school rules!

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I think little math + VOP all right

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It has been a long while

And today I had need of this, and decided to try again. I think I got it working!

It's barebones and not tested extensively (it's waay past bedtime!), would love to hear if there is something I missed!

I got the solution from: http://www.flipcode.com/documents/matrfaq.html#Q40

`Q40. How do I use matrices to convert one coordinate system to another?`

Hi Alvin,

i am a Houdini beginner and just dived into your file in order to learn from it (because this CoordinateSpaceTransformations/Virtual Parenting is something that always hooks me when it comes up).

The only thing that i don´t understand really is the very first node called "non_procedural_geometry", in which you built your source geo from a triangle and use that 3 points to build your Transform Matrix later.

How would i go doing the same from an arbitrary mesh, or even better, from a file-SOP with an imported already animated and baked geo?

can you give me a hint?

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It has been a long while

And today I had need of this, and decided to try again. I think I got it working!

It's barebones and not tested extensively (it's waay past bedtime!), would love to hear if there is something I missed!

I got the solution from: http://www.flipcode.com/documents/matrfaq.html#Q40

`Q40. How do I use matrices to convert one coordinate system to another?`

Hi Alvin. I just wanted to thank you for sharing this. It has been really helpful for me lately.

@nautiluz: In case you are still wondering: Setup a interface where you can set the three reference points that goes into the local space creation. Make sure they represent a flat triangle on the baked geometry.

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Whoops, sorry, didn't realize there were replies in the thread! I swear I have follow topic engaged and didn't get any emails :-/

Sadly I need this posted hip () for some stuff at work, will reply shortly!

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Whew ok this saved my butt. Anyways, using Extract Transform (this is new-er right? There was another node that required you to put in the points to track?) wasn't working for me, I always have the attached object sliding around. I'm probably doing something wrong.

Also, you can concatenate multiple transforms into one matrix, which makes it highly convenient.

With regards to Align, that's a cool sop! Totally missed it. Sadly, from my tests the aligned geo kept sliding around so I need to figure out where I'm using it wrongly.

@nautiluz: Sorry the reply is so late. But if you replace non-procedural geo with any deforming model with a non-changing point count, it should work.

@Ole: I'm glad it helped! This just saved my butt 5 minutes ago

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On 10/23/2014 at 5:00 PM, GallenWolf said:

It has been a long while

And today I had need of this, and decided to try again. I think I got it working!

It's barebones and not tested extensively (it's waay past bedtime!), would love to hear if there is something I missed!

I got the solution from: http://www.flipcode.com/documents/matrfaq.html#Q40

```
Q40. How do I use matrices to convert one coordinate system to another?```

Thank you very much. This helped a lot

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