hongsing.tang

hi guys, i am a newbie Houdini user here, pardon my newb-ness. Recently I've inherited a houdini project from my senior and my boss wants me to export a working animation from this project to Unreal Engine (FBX format)(im using HoudiniFX, licensed version, its really in an ungodly messy-state rn).

I kept facing an error "Failed to traverse rig geometry for export: No valid roots found" while using the 'rop_fbxcharacteroutput1' node. I checked that the 'rest geometry' and 'capture pose' inputs are fine. 'rest geometry input' being the armour mesh's 1st frame (static, not animated) and 'capture pose' input being the bone's static pose (1st frame too) . when these two inputs are solely connected to 'rop_fbxcharacteroutput1' node, the Save To Disk function/button works normally. However when i attach an Animated Pose input into the rop_fbxcharacteroutput1 node and press Save To Disk, the error "failed to traverse rig..." flags up. Initially there was a name attribute error thing but i saw another forum post and used Name SOP to fix that. I have been trying to export this project as an FBX for 2-3 days now. please any one, any help and any advice would be much appreciated here.

My .hip file is attached here: if you need to see the god forsaken workflow/ nodes. Unfortunately the file caches is local to my PC and is too big to upload here i guess. thanks anyone yet again

hello all. the aim of this entire exercise is to get Mn, from
Vn * V0(inversed) == Rn
Rn * M0 == Mn <------ what we want

where Vn is a (3x3) matrix i construct by selecting 3 vectors connected to a common root pivot in an arbitary nth frame.

V0 is a (3x3) matrix i construct from the same 3 vectors selected to the same root pivot in the 1st frame.
Heres how i intend to construct the 3 selected vectors on an armour of my model, by selecting a pivot point (E.g point 4).
arbitary_point1 - point 4 == vector 1,
arbitary_point2 - point 4 == vector 2,
arbitary_point3 - point 4 == vector 3.
use this to form (3x3) matrix -> V0

M0 is the rotation matrix i need from the 1st frame. However i do not know where to obtain this matrix.

I used a RigDoctor midway through my workflow and got localtransform and transform attributes.



The localtransform is a 4x4 homogenous matrix (which can easily separate the rotation matrix from the translation vector) according to this website/ documentation "https://mecharithm.com/learning/lesson/homogenous-transformation-matrices-configurations-in-robotics-12 [mecharithm.com]"

In this case, the rotation matrix extracted (lets call this M0) would be a (3x3) from r11 to r33 in the picture. However this values are local to parent values instead of local to world space values (which i want).

On the other hand, the other transform matrix (3x3) as seen on the right side of the Geometry spreadsheet image is already a local to world values (i assume according to its large values). However I searched the RigDoctor node documentation and it does not have any mention of explaining the localtransform/ transform attributes derivation/ calculation. I am afraid it consist of translation, rotation and scale values all mixed together in the (3x3) as displayed in the geometery spreadsheet. I search around and thought it may be possible to extract the rotation matrix from this (3x3) with this solution online

"https://math.stackexchange.com/questions/237369/given-this-transformation-matrix-how-do-i-decompose-it-into-translation-rotati [math.stackexchange.com]"


However i need abit more clarification on how to get M0, do i get the rotation matrix (3x3) from the root POINT of the localtransform(4x4) homogenous matrix from the 3 arbitary vectors i've selected for that armour? (this is local values) or do i get the M0 rotation matrix from the (3x3) transform matrix (world coordinates, but may consist of translation and scale values)? Any advice or help or questions would be much appreciated! idk who else to ask. thanks a million