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BTrace Mesh Follow results in curve rolled into a ball
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Description

System Information
Windows 8.1 64 bit; EVGA GTX 970

Blender Version
Broken: (2.79 5bd8ac9)

Short description of error

Hi there,

I'm not sure if this is a bug or a limitation of the addon. Here's what I'm trying to do:

I have an empty following a path, by manually animating the path's evaluation time. I have a cube that is the child of the empty. I select the cube, then select Mesh Follow. Start frame is 256, end frame is 406, same as my timeline. I have selected to trace the Object's origin. Upon clicking "Run", the resulting curve is a twisted up ball far from its starting location. Is this happening because the addon does not recognize an animated parent? Thanks!

Details

Type
To Do

Event Timeline

Here are my settings:

This seems to be a known limitation.

You can find this is in the sourcecode

Mesh Follow, trace vertex or faces
Create curve at center of selection item, extruded along animation
Needs to be an animated mesh!!!

it uses ob.location.copy() so constraints, curve parents etc wont work.
( Could be a rather easy change, but this is more of a TODO )

As a workaround you can Bake Action with Visual Keying option to get keyframes (which then BTrace will handle nicely...)

Philipp Oeser (lichtwerk) triaged this task as Normal priority.Jan 26 2018, 10:00 PM

I'll leave this open (but change to TODO) for the time being because I dont know if we have a place on the TODO wiki for addons as well...

Philipp Oeser (lichtwerk) changed Type from Bug to To Do.Jan 26 2018, 10:00 PM

could try a fix... open the file: scripts\addons\btrace\bTrace.py
in lines 669 and 673 change 'matrix_local' to 'matrix_world', that will fix it for vertex and face tracers
change line 684 'g_co = objindex.location.copy()' to 'g_co = objindex.matrix_world.to_translation()'
that is for the object tracer to work

Thanks Philipp for the information and the tip about baking the action first. Also thanks lower case for the python code info... I will have to try that.