OP2 Difference in xyz values.

[Calvin]

Hey,

I'm loading an OP2 file using the command:
from pyNastran.op2.op2 import read_op2
read_op2(filename, load_geometry=True, build_dataframe=True)

I then recreate the mesh using pyvista and the data from the nodes and elements. On some files the recreated meshes look very distorted. 

I opened the same files with the pyNastranGUI and they do not look distorted at all. I chose some nodes at random and found that the GUI had different xyz values to those loaded with pure python. For example:

model.nodes[10218141].xyz

array([-146.11399841, -510.27200317, -101.31700134])

whereas probing the node in the GUI:

NodeID = 10218141; xyz=(-132.83604431152344, -526.622314453125, -101.6064453125); pierce_xyz=(-133.03369240275018, -526.7144295913313, -102.14456481433325) 

Majority of the nodes match, it's just certain ones. Any idea what the reason for the difference could be?

Thanks,

Calvin

[Steven Doyle]

There are a lot of steps in there so I’d need to see a model.  Coordinate systems. Offsets.  Pick tolerance 

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[Calvin]

Will confess to being a programmer rather than an engineer! 

The file is the same for both. Does the GUI not use the read_op2 function to read the file? I can't see any options to specify coordinate systems etc. there? How can I find which coordinate systems etc. that you mention are being used?

[Steven Doyle]

You don’t specify coordinate systems in the gui.  They’re in the bdf and they’re copied to the op2.

Node.xyz for node 1 could be in a cylindrical frame and node 2 could be in a spherical frame.  All nodes are transformed to global (coord=0) to display the model.  My guess is you have a coordinate system.  Check your bdf.

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