[x3d-public] Specification editors meeting: 3 mantis issue corrections, 2 issues for review

Fri Jul 2 03:49:07 PDT 2021

Don,

I would not really go into saying in spec: "SFMatrix3xxx" is for 2D
transformations, and "SFMatrix4xxx" is for 3D transformations, because
the reality is more complex :)

- 2D matrix can be used to express 2D rotation and scaling (but not
translation).
- 3D matrix can be used to express all 2D transformations (including
rotation, scale, translation). Or it can be used for 3D rotation and
scaling (but not translation), which is useful e.g. to transform
normal or tangent vectors.
- 4D matrix can be used to express all 3D transformations (including
rotation, scale, translation) thanks to using homogeneous coordinates
to express 3D points/directions as 4D vectors.

This is a large topic, and basically touches "how to use matrix and
vectors for 2D and 3D graphics" :)

Regards,
Michalis

czw., 1 lip 2021 o 20:17 Don Brutzman <brutzman at nps.edu> napisał(a):
>
> 4. Dick and I continued resolving editorial fixes today.
>
> a. Mantis 405: 37.4.10 RigidBody -- Mismatched Definition of inertia matrix
>
> We cleaned up the definition to match SFMatrix3f functionality, and deleted extraneous sentences about too few/too many SFMatrix3f values.
>
> "The inertia field represents a 3x3 inertia tensor matrix."
>
> ---
>
> b.  We cleaned up a degenerate default rotation axis, again in RigidBody.
>
> Mantis 1366: 37.4.10 RigidBody: degenerate default value for finiteRotationAxis
>
> Field signature
>    SFVec3f [in,out] finiteRotationAxis 0 0 0 [-1,1]
>
> is an ill-defined default axis. Modified to
>
>    SFVec3f [in,out] finiteRotationAxis 0 1 0 [-1,1]
>
> ---
>
> c. We clarified Matrix3 and Matrix4 field type definitions.
>
> Mantis 1367: Clarification for Matrix3 and Matrix4 type definitions
>
> Need to clarify that Matrix3 and Matrix4 type definitions commonly apply to 2D and 3D transformations, respectively.
>
> Example:
> 5.3.8 SFMatrix3d and MFMatrix3d
> [...]
> "SFMatrix3d matrices are organized in row-major fashion. The first row of the matrix stores information for the x dimension, and the second for the y dimension. Since these data types are commonly used for transformation matrices, translation values are stored in the third row."
>
> Modification: "used for /2D/ transformation matrices"
>
> Applied corresponding changes (2D and 3D respectively) for
>
> 5.3.8 SFMatrix3d and MFMatrix3d
> 5.3.9 SFMatrix3f and MFMatrix3f
> 5.3.10 SFMatrix4d and MFMatrix4d
> 5.3.11 SFMatrix4f and MFMatrix4f
>
> ---
>
> On 6/29/2021 11:05 AM, Don Brutzman wrote:
> > 1.  We added the following to X3D4 public page
> >
> > a. X3Dv4 Public Working Draft
> >     https://www.web3d.org/x3dv4-public-working-draft
> >
> > "On 17 May 2021, ISO/IEC Joint Technical Committee (JTC)1 Standards Committee (SC) 24 national body members voted to approve renewal of X3D4 Architecture with next stage being Committee Draft (CD).  Web3D Consortium efforts to apply whitespace corrections and editorial refinements continue on the X3D4 Committee Draft (CD1) Specification (also .zip)."
> >
> > b. X3D4 Committee Draft (CD1) Specification
> >     https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-CD1/
> >
> > We have asked whether it is all right for subsequent editorial changes to also be posted publicly.  This can continue support for thoroughly correct X3D4 implementations.
> >
> > ---
> >
> > 2. Mantis review and application of comments
> >
> > a. Mantis 314: 35 Layering component - derivation Question
> >     https://www.web3d.org/member-only/mantis/view.php?id=314
> >
> > Viewport fixed, removed redundant X3DBoundedObject interface.
> >
> > No problems found with X3DLayerNode or Layer.
> >
> > ---
> >
> > b. Mantis 399: 37.4.9 MotorJoint -- Missing Definitions
> >     https://www.web3d.org/member-only/mantis/view.php?id=399
> >
> > Paragraph 4 refined as follows:
> >
> > The three axis-angle fields axis1Angle, axis2Angle and axis3Angle provide angles (in angle base units) for this frame for the corresponding motor axis when in user-calculated mode. The three axis-torque fields axis1Torque, axis2Torque and axis3Torque define the torque value applied about each axis.
> >
> > ---
> >
> > c. Mantis 401: 37.4.10 RigidBody -- Missing Definition
> >     https://www.web3d.org/member-only/mantis/view.php?id=401
> >
> > Resolved by adding field names near beginning of already-existing explanation:
> >
> > "The damping factor fields, linearDampingFactor and angularDampingFactor, allow the user to instruct the implementation to automatically damp the motion of the body over time. The value of the field is used to take a multiple of the value calculated in the last frame and apply it in opposition to the current motion for this frame. Damping is useful to provide an appearance of frictional forces and also to prevent the body from exploding due to numerical instability of the physics model calculations. Damping is proportional to the current velocity and/or rotation of the object. The application of damping is controlled through the use of the autoDamp field. When the value is FALSE, no damping is applied. When the value is TRUE, rotational and translational damping is calculated and applied."
> >
> > ---
> >
> > 3. Topics for next X3D Working Group meeting: group review to ensure everything AOK.
> >
> > a. Mantis 261: 04.4.4 Prototype semantics - Formal Support for appinfo and documentation fields
> >     https://www.web3d.org/member-only/mantis/view.php?id=261
> >
> > It looks like all the work has been done to add the already-approved 'appinfo' and 'documentation' fields to ProtoDeclare.
> >
> > b. Four Mantis issues are open relative to Clipping Plane prose: 1238, 702, 326, 190
> >
> > We will continue processing editorial Mantis issues at each meeting.
>
> all the best, Don
> --
> Don Brutzman  Naval Postgraduate School, Code USW/Br       brutzman at nps.edu
> Watkins 270,  MOVES Institute, Monterey CA 93943-5000 USA   +1.831.656.2149
> X3D graphics, virtual worlds, navy robotics http://faculty.nps.edu/brutzman
>
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