# Convert a C3d and TRC files to BVH

I have two files one .bvh and the other is .c3d and I want to convert them to .bvh files if anyone could please advise how to do this as I need to work on bvh only.

• Can you provide both files for testing? You can import the .c3d into blender and export it as .bvh. stackoverflow.com/questions/20499320/… – Jaroslav Jerryno Novotny May 14 '15 at 9:12
• @Jerryno this is the c3d file dropbox.com/s/dfmi0wffsurl0ae/file.c3d?dl=0 and in the link you provided it shows how to import .c3d file into blender (which I already did), my problem is how to convert it into .bvh – Tak May 14 '15 at 9:18
• Could also look at convert-x.pp.ua/?convert&from=c3d&to=bvh – batFINGER Mar 13 '16 at 17:04
• @batFINGER I've tried it but once I try to unzip the compressed file it needs a password, any thoughts? – Tak Mar 14 '16 at 3:09
• @batFINGER did you have the chance to check my previous comment? – Tak Mar 15 '16 at 9:41

You can import .c3d file in blender like this:

https://stackoverflow.com/questions/20499320/how-to-import-c3d-files-into-blender

The problem is it won't be an armature, but animated locations of points:

Some points will be dead in the center (marked).

1. Adjust the frame range to fit the mocap data
3. Re-build the armature - add armature to scene

• looks like we have markers from both sides for each leg - that means the bones will be somewhere in between markers

• Building the armature:

• select a marker (or two if I want position in between) and align 3D cursor with 'Shift-S > Cursor to Selected'
• then enter edit-mode of armature and select a joint and 'Shift-S > Selection to Cursor'
• this way I can place all the bones (joints) precisely

• also recalculate the Roll of the bones with 'Ctrl+N > Cursor' with 3D cursor on some reference marker

• Name the bones properly

• Constraining location of root bones:

• use copy_location constraint
• or two of them with second on 50% influence to get in-between position of two markers
• similar for center of 3 markers, you get the idea
• Constraining bones direction

• use damped_track constraint
• also multiple of them with adjusted influence for center of group of markers

4. Bake the animation to Action with Pose > Animation

Bake Action: visual_keying_ON, clear_constraints_ON

5. Export armature as .bvh from the blender main menu (you might need to enable BVH addon).

These steps will result in having a .c3d file converted to a .bvh file. A sample .blend file with rigged markers here:

• Is it possible to share with me a file with the modified steps so that I can go through them and have a reference? – Tak May 15 '15 at 1:37
• @shepherd yep, I'll rig one leg or something and give the .blend. I suspect this is a dog am I right? (for anatomy reference) – Jaroslav Jerryno Novotny May 15 '15 at 5:27
• @shepherd, yep, you only add 1 armature object to the scene and then you add bones to it in edit-mode (Tab). You can extrude a bone from a joint with E or add a new bone to 3D cursor location with Shift-A. This way you end only with 1 object with multiple bones inside.) If you have multiple armatures you can fix it with selecting them and joining them into one with Ctrl-J – Jaroslav Jerryno Novotny May 16 '15 at 18:37
• Thank you very much again. I've been using these steps manually but now I need a script as I have many files. I've followed the answer below given by batFINGER and constructed the armature found here dropbox.com/s/nx8xsk4z0pavaxx/ArmatureToTpose.blend?dl=0 then I try to put the armature in Tpose to parent to my mesh with automatic weighting using the batFINGER's answer found here blender.stackexchange.com/a/53981/2517 you will find that the mesh is doesn't look good, kinda twisted and during the animation it get's ugly, I'm not sure why? is it because of the bone roll value? – Tak Nov 19 '16 at 9:31
• so as you suggested, I've used DAMPED_TRACK instead of TRACK_TO used by batFINGER. And the mesh still looks bad using con = pb.constraints.new('DAMPED_TRACK') con.target = bpy.data.objects.get(pb.name) con.track_axis = 'TRACK_Y' con.influence = 1 – Tak Nov 19 '16 at 9:33

Created a script to create a hierarchal armature and add constraints to animate.

Firstly import the c3d with a prefix, I've chosen "GT_", this makes it easier to clean up.

import bpy
context = bpy.context
scene = context.scene
prefix = "GT_"
# select all imported with prefix GT_
obs = [o for o in scene.objects if o.name.startswith(prefix)]
root = "RootDog"

# clean up unwanted objects could look for flat action sum.

text = bpy.data.texts.get("C3D_bones")
if not text:
text = bpy.data.texts.new("C3D_bones")

text.clear()

bones = {}
for o in obs:
if o.location.length < 0.0000001:
bpy.data.objects.remove(o)
else:
name = o.name[3:]
print(bones)
bones[name] = {"parent":None,
"tail":root}

names = sorted(bones.keys())
text.write("%s\n" % root)
for name in names:
if name == root:
continue
text.write("\t%s\n" % name)


It creates a text object with a simple structure. Tabs must be used to indent. Like

RootDog
LBackElbow
LBackLeg
LBackPaw


Which was quite simple to edit into, and I renamed to "C3DBones.txt" to avoid overwriting with previous script.

RootDog
RFrontWaistDog
RBackWaistDog
RBackElbow
RBackLeg
RBackPaw
LFrontWaistDog
LBackWaistDog
LBackElbow
LBackLeg
LBackPaw
LowBackDog
MidbackDog
TopSpineDog
RFShoulderDog
RElbowDog
RForeLeg
RPaw
LFhoulderDog
LElbowDog
LForeLeg
LPaw


Lastly, the hierarchy is used to create a rig and add constraints.

import bpy
from mathutils import Vector
context = bpy.context
scene = context.scene

text = bpy.data.texts.get("C3D_bones.txt")
prefix = "GT_"
parent_level = 0
parents = [None] * 16

arm = bpy.data.armatures.new("Armature")

rig = bpy.data.objects.new("C3DRig", arm)
scene.objects.active = rig
scene.update()
bpy.ops.object.mode_set(mode='EDIT')

for l in text.lines:

body = l.body
level = 0
while body.startswith("\t"):
body = body[1:]
level += 1
print(l.body, level)
body = "%s%s" % (prefix, body)
bone = arm.edit_bones.new(body)

o = scene.objects.get(body)
if not o:
print("No %s" % body)
continue

bone.tail = o.location
parent_level = max(level-1, 0)
parents[level] = o
parent = parents[parent_level]

bone.parent = arm.edit_bones.get(parent.name)
if bone.parent:

bone = arm.edit_bones.get(parents[0].name)
if bone:
bone.head = bone.tail + Vector([0, 0, 1])
bpy.ops.object.mode_set(mode='OBJECT')
else:
print("no root bone")

# do something with pose bones

for pb in rig.pose.bones:
con = pb.constraints.new('COPY_LOCATION')
if not pb.parent:
con.target = bpy.data.objects.get(pb.name)
continue

con.target = bpy.data.objects.get(pb.parent.name)
con = pb.constraints.new('TRACK_TO')
con.target = bpy.data.objects.get(pb.name)


• Thanks for that. Could you send me a link of the blend file please? – Tak Mar 23 '16 at 2:25
• Done, note it only creates a rig and animates it off the c3d empties. Connect bones where desired and add limit rot constraints etc to fix bone roll, or use the methods suggested by @Jerryno. Also the root bone loc is kinda crap. Might need to add a constrained empty half way between the waists and use that instead of RootDog. Once that is done I'd pose into a rest position, and change to this rest pos. (currently has the rest pose of the pose of the frame on which the 2nd script is run) – batFINGER Mar 23 '16 at 3:52
• Sample with tween waist empty as root. pasteall.org/blend/41189 – batFINGER Mar 23 '16 at 5:59
• Is it possible to make the constructed root bone very small so it's not visible? I've tried doing this from the 3d view and it looks like this can be done by going to editmode then selecting the tail of it and then translating it by -1 along the Z-axis. – Tak Nov 14 '16 at 11:58
• I was able to solve it using context.object.data.edit_bones[0].select_head = True then bpy.ops.transform.translate(value=(0, 0, -0.99), constraint_axis=(False, False, True), constraint_orientation='GLOBAL', mirror=False, proportional='DISABLED', proportional_edit_falloff='SMOOTH', proportional_size=1) {'FINISHED'} – Tak Nov 14 '16 at 12:42