Matrix

There's anyone can tell ne how work the matrix comand? If i have a 15 cube in the model space can i obtain a matrix of they position? (Rotation,traslation)
Sorry for my english
Thanks a lot

Replies to This Discussion

Permalink Reply by David Rutten on August 26, 2012 at 1:47pm

0.9+

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Daniel de Berna on August 27, 2012 at 6:47am

I got to try your definition:
the original cube and the one obtained by the rotation were created in grasshopper, you can assign existing models?
Let me explain: in R design my cubes in different positions that interest me, then I get the matrix for each cube ...

Great

Permalink Reply by Daniel de Berna on August 28, 2012 at 3:46pm

I David i hope you can help me one more time!

In the Jpg you can understand the problem..please help!!

Attachments:

Permalink Reply by David Rutten on August 28, 2012 at 4:19pm

I don't think reversing the lines at that late stage will work. All the numbers in the matrix are related to each other so you'd have to figure out how to modify all of them. I'm afraid we've now left my comfort zone when it comes to transformation matrices, maybe one of the Octane developers knows how to rewrite the matrix so that the Y and Z are flipped.

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Daniel de Berna on August 29, 2012 at 12:59am

Thank you very much, I've been a big help!
I am able to copy an object as many times as I want, with your help, the only thing that does not work when objects rotate around the Z axis .... but that's okay!

thanks again

Permalink Reply by Daniel de Berna on August 31, 2012 at 3:23am

I david,

Can you tell me what point of reference, uses your script to find the coordinates of the object? Use the center of the base or a corner?

The coordinate is calculated according to the origin right?

Thanks

Permalink Reply by David Rutten on August 31, 2012 at 7:09am

I get a list of all the topological vertices of the Brep object. Then, assuming two breps have the same topology, I construct a plane from the first three vertices. Vertex[0] becomes the plane origin. Vertex[1] becomes the X-Axis and Vertex[2] will provide the last point to lock down the plane.

Since we're only interested in relative transformation, it's irrelevant where you define these planes, as long as you do it in the same way for each object.

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Daniel de Berna on August 31, 2012 at 7:43am

Thanks David...one more time :D

I can not understand why in rhinoceros get one thing, and in Octane render it I get a completely different.
Any idea?

Attachments:

Istanza_Def.gh, 17 KB

Permalink Reply by David Rutten on August 31, 2012 at 8:12am

Seems like the rotation center point is off. In Rhino transform matrices "act on the left". If Octane matrices act on the right, then the order of transformations may be off giving you the result as though rotation happened. Think of it like this, the Transformation Matrix defined two operations; a translation and a rotation. The rotation part contains a center point and an angle. If you Rotate first, then Move, you get a different result from when you Move first then Rotate:

The green shape is the source geometry and the blue shape is the target geometry. The black circle is the rotation center point. When you create a transformation matrix in Rhino, it is made in such a way that it will be correct only if you rotate first, then move. If you invert these two operations you end up with the case on the right, where the final dashed rectangle is not coincident with the blue rectangle. It looks like this might be the case in the image you posted. But I could well be wrong.

As I said, we're definitely past my grip on matrices here, you need to find someone who truly understands the mathematics behind them and who knows how to convert a left-acting one to a right-acting one.

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Daniel de Berna on September 2, 2012 at 2:37pm

you can create a box in a top and not according to the center of its base?

in my definition I can create a box according to the center, given a point!
I would like to, given a point, create the box in the top.