Rigids 3 tutorial Matrix math

[lubitel]

I am doing the Rigids 3 helicopter crashing tut and am kind of stuck. Steven is brief in explaining this part identity matrix. I wish it was broken down further.

I store the current P as oldP, unpack, zero all the transforms, move to world origin, clean attribs, repack and put them back to the oldP. However parts of the geometry dont make back to the oldP. It is the parts that were prefractured by voronoi.

I think it is ither in the unpacking or one of the attrib promotes that needs to be adjusted. I am just not sure what is going on under the hood... argh!

 

Helly_01.hip

Edited April 12, 2017 by lubitel
presision

[derjcmp]

I can't open your file atm. Are you transfering the attributes on the unpack and on the pack ?

I went through you're file and didndt see manage to restore it either way. Go through the provided scene files and try to see what you did wrong. I think the naming of the pieces must be wrong. Also the cleanSOP was deleting all primitives. 

Edited April 12, 2017 by derjcmp

[lubitel]

I downloaded the file and it opened for me here on H16.0.557....It may take some time to open the file as I locked the incoming fractured geo so you can have source file. And the display flag should be on the node right before the last NULL. "restoring_oldP"

On the second image you can see the params on pack and unpack nodes.. cheers

 

Edited April 12, 2017 by lubitel
clarity

[adrianr]

You haven't repacked the geometry in your initial Foreach loop on the Assemble sop. You unpack it to do the fracture but you need to check 'Create Packed Geometry' on the Assemble sop so the result of the Foreach is packed chunks. This is crucial to the zeroP trick as it's actually zeroing the chunks packed centroid, not every point on the geometry. These points have things known as intrinsics, so Houdini knows what those points are referencing, where they are, their orientation, etc (Hit the 'Intrinsics' drop down on the geometry spreadsheet with a node that had packed geo, there are loaaaaaads).

Sorry for messy explanation if you need me to break it down more I will be happy to do so tomorrow  

Also turn off 'Vizualise Peices' on the Voronoi Fracture node if you want to maintain the colours you gave the geo coming into the loop. 

[lubitel]

I forgot to check the Create Packed Geometry flag Thanks so much Adrian.
The Itrinsics is still a mystery to me thou. If you could break it down further that would be fantastic.

 

Cheers

[lubitel]

Getting there inch by inch

heli-Desktop.m4v