Techniques - Revision history

Flux: avoid https encryption slowdown in links

2015-12-14T15:38:40Z

avoid https encryption slowdown in links

Cxo eoso at 18:23, 23 April 2014

2014-04-23T18:23:49Z

Cxo eoso at 17:53, 23 April 2014

2014-04-23T17:53:54Z

Cxo eoso: pasted BVH to X3D content here

2014-04-23T17:52:05Z

pasted BVH to X3D content here

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Cxo eoso: wordsmithed the bullets here and there

2014-04-23T17:49:10Z

wordsmithed the bullets here and there

Cxo eoso: Created page with "===How to convert=== TODO: the remaining section has extra information that can be integrated into the preceding sections. With a little more work, we can then combine the p..."

2014-04-23T17:25:36Z

Created page with "===How to convert=== TODO: the remaining section has extra information that can be integrated into the preceding sections. With a little more work, we can then combine the p..."

New page

===How to convert===

TODO: the remaining section has extra information that can be integrated into the preceding sections.

With a little more work, we can then combine the pieces to show corresponding animations in HAnim and BVH.
We can build an application program that uses these mappings.
* This conversion program operates off-line, not within an X3D scene, because X3D does not allow reading files.

Wikipedia articles of interest:
* [http://en.wikipedia.org/wiki/Conversion_between_quaternions_and_Euler_angles Conversion between quaternions and Euler angles]
* [https://en.wikipedia.org/wiki/Rotation_formalisms_in_three_dimensions Rotation formalisms in three dimensions]
** 1.2 Euler axis and angle (rotation vector) matches the X3D SFRotation
** 2.2 Rotation matrix ↔ Euler axis/angle

It looks like choosing the right matrix operations will perform this conversion. This requires careful composition of rotation matrix operations.

← Older revision		Revision as of 18:23, 23 April 2014
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	** 2.2 Rotation matrix ↔ Euler axis/angle		** 2.2 Rotation matrix ↔ Euler axis/angle

−	~~It looks like choosing~~ the right matrix operations will perform this conversion. ~~This requires~~ careful ~~composition of~~ rotation matrix operations.	+	Choosing the right matrix operations will perform this conversion. Be careful composing rotation matrix operations.
		+
		+	==Procedure for H-Anim character design==
		+	* [http://web3d.org/wiki/index.php/File:ProcedureCharacterDesign130911.pdf Procedure for designing an H-Anim character with a general design tool]
		+
		+	==H-Anim wrl to x3d converter==
		+	* [http://web3d.org/wiki/index.php/File:HAnimWRL_X3D_Converter130905.zip Converter from H-Anim WRL to H-Anim X3D]
		+	* test version

← Older revision		Revision as of 17:53, 23 April 2014
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		+	== BVH mocap conversion to X3D interpolators ==
		+
		+	Myeong Won Lee example: http://web3d.org/wiki/images/4/4b/197_a.bvh.txt
		+
		+	Proposed investigation procedure: divide and conquer! Let's take each skeleton apart and put them back together again.
		+
		+	----
		+	===1. Is there an X3D H-Anim skeleton that corresponds to the BVH ROOT/JOINT HIERARCHY? ===
		+
		+	The structures used by BVH and H-Anim are different. There is not a direct correspondence between them. Differences include:
		+	* The hierarchical nesting of parent-child relationships is different
		+	* Values are therefore in different coordinate frames (one might be relative to parent joint, the other absolute coordinates for the human)
		+	* Formats are quite different
		+	* (others will be listed here)
		+
		+	----
		+	=== 2. However many similarities also exist. Maybe they can be exploited? ===
		+
		+	Perhaps we can build a mapping between the two. If we perform rotation transformations, a conversion algorithm can be computed for each hierarchy and corresponding units.
		+
		+	Here is a possible set of correspondences between a BVH model and an X3D H-Anim LOA-1 model.
		+
		+	* '''BVH :: X3D H-Anim'''
		+	** ROOT :: HAnimHumanoid
		+	** JOINT :: HAnimJoint
		+	*** JOINT name:: HAnimJoint name
		+	*** OFFSET :: HAnimJoint center
		+	** CHANNEL definitions :: HAnimJoint rotation, translation
		+	*** MOTION array of Euler-degree rotations :: OrientationInterpolator MFRotation array with ROUTE connections
		+	*** CHANNEL array of position translations :: PositionInterpolator MFVec3f array with ROUTE connections
		+	** End Site :: HAnimSite
		+	** Anything else?
		+
		+	TODO
		+	* map the BVH names to the approved H-Anim X3D names.
		+
		+	----
		+	=== 3. Once we have the skeleton mapping, we can work on the animation values. ===
		+
		+	Let's look at the BVH file next. Hypothesis:
		+	* BVH MOTION arrays providing Zrotation Xrotation Yrotation values
		+	to
		+	* corresponding MFRotation arrays with 4-tuple SFRotation values
		+
		+	Example reconstruction follows. First is an extract from the BVH file, then a counting exercise of how many floats appear.
		+
		+	* ROOT Hips
		+	CHANNELS 6 Xposition Yposition Zposition Zrotation Xrotation Yrotation
		+	* JOINT Chest
		+	CHANNELS 3 Zrotation Xrotation Yrotation
		+	* JOINT LeftCollar
		+	CHANNELS 3 Zrotation Xrotation Yrotation
		+	* JOINT LeftShoulder
		+	CHANNELS 3 Zrotation Xrotation Yrotation
		+	* JOINT LeftElbow
		+	CHANNELS 3 Zrotation Xrotation Yrotation
		+	* JOINT LeftWrist
		+	CHANNELS 3 Zrotation Xrotation Yrotation
		+	* JOINT RightCollar
		+	CHANNELS 3 Zrotation Xrotation Yrotation
		+	* JOINT RightShoulder
		+	CHANNELS 3 Zrotation Xrotation Yrotation
		+	* JOINT RightElbow
		+	CHANNELS 3 Zrotation Xrotation Yrotation
		+	* JOINT RightWrist
		+	CHANNELS 3 Zrotation Xrotation
		+	* JOINT Neck
		+	CHANNELS 3 Zrotation Xrotation Yrotation
		+	* JOINT Head
		+	CHANNELS 3 Zrotation Xrotation Yrotation
		+	* JOINT LeftHip
		+	CHANNELS 3 Zrotation Xrotation Yrotation
		+	* JOINT LeftKnee
		+	CHANNELS 3 Zrotation Xrotation Yrotation
		+	* JOINT LeftAnkle
		+	CHANNELS 3 Zrotation Xrotation Yrotation
		+	* JOINT RightHip
		+	CHANNELS 3 Zrotation Xrotation Yrotation
		+	* JOINT RightKnee
		+	CHANNELS 3 Zrotation Xrotation Yrotation
		+	* JOINT RightAnkle
		+	* CHANNELS 3 Zrotation Xrotation Yrotation
		+
		+	Defines a MOTION array consisting of numeric values:
		+
		+	3 floats [Hip location]
		+	3 floats [Hip rotation]
		+	3 floats [Chest rotation]
		+	3 floats [LeftCollar rotation]
		+	3 floats [LeftShoulder rotation]
		+	3 floats [LeftElbow rotation]
		+	3 floats [LeftWrist rotation]
		+	3 floats [RightCollar rotation]
		+	3 floats [RightShoulder rotation]
		+	3 floats [RightElbow rotation]
		+	3 floats [RightWrist rotation]
		+	3 floats [Neck rotation]
		+	3 floats [Head rotation]
		+	3 floats [LeftHip rotation]
		+	3 floats [LeftKnee rotation]
		+	3 floats [LeftAnkle rotation]
		+	3 floats [RightHip rotation]
		+	3 floats [RightKnee rotation]
		+	3 floats [RightAnkle rotation]
		+	= 19*3 = 54 floats
		+
		+	Each line of the MOTION data has 19 triples. Therefore we do have a good match.
		+
		+	----
		+
		+	=== 4. Units ===
		+
		+	Length
		+	* BVH position units: author-defined, arbitrary - no fixed units, apparently (TODO confirm)
		+	* X3D position units: 3-tuple x-y-z meters relative to point between feet on floor
		+
		+	Some scaling may be needed to get from BVH to X3D, either by a Transform scale or by a UNIT statement.
		+
		+	Angle
		+	* BVH orientation units: (Zrotation Xrotation Yrotation) Euler angles in degrees. Note that order may vary. (TODO confirm)
		+	* X3D rotation units: SFRotation 4-tuple (normalized x-y-z axis vector, angle in radians)
		+
		+	Given these definitions, we will need to convert the BVH orientation to X3D rotation.
		+	Ordinarily in 3D graphics this is performed using a 3x3 or 4x4 transformation matrix.
		+
	=== 5. Converting BVH Motion Arrays to X3D Interpolators ===		=== 5. Converting BVH Motion Arrays to X3D Interpolators ===

@@ Line 356: / Line 356: @@
 Germane Wikipedia articles:
 * [http://en.wikipedia.org/wiki/Conversion_between_quaternions_and_Euler_angles Conversion between quaternions and Euler angles]
-* [https://en.wikipedia.org/wiki/Rotation_formalisms_in_three_dimensions Rotation formalisms in three dimensions]
+* [http://en.wikipedia.org/wiki/Rotation_formalisms_in_three_dimensions Rotation formalisms in three dimensions]
 ** 1.2 Euler axis and angle (rotation vector) matches the X3D SFRotation
 ** 2.2 Rotation matrix ↔ Euler axis/angle

@@ Line 1: / Line 1: @@
 ===How to convert===
-TODO: the remaining section has extra information that can be integrated into the preceding sections.
+TODO: this section has information that complements the preceding sections.
-With a little more work, we can then combine the pieces to show corresponding animations in HAnim and BVH.
+We can combine the pieces to show corresponding animations in HAnim and BVH.
 We can build an application program that uses these mappings.
 * This conversion program operates off-line, not within an X3D scene, because X3D does not allow reading files.
-Wikipedia articles of interest:
+Germane Wikipedia articles:
 * [http://en.wikipedia.org/wiki/Conversion_between_quaternions_and_Euler_angles Conversion between quaternions and Euler angles]
 * [https://en.wikipedia.org/wiki/Rotation_formalisms_in_three_dimensions Rotation formalisms in three dimensions]