[x3d-public] X3D meeting minutes 20 July: near/far clipping, Python SAI, medical, ISO, SIGGRAPH
GPU Group
gpugroup at gmail.com
Fri Jul 20 11:36:12 PDT 2018
WEB3D.ORG SPEC COMMENT RULES APPLY, PUBLIC CHECKBOX CHECKED >>>
near / far clipping planes > geo tearing >
in freewrl I detect geo range automatically and iterate over up to 3 depth
slices
default: .1 21000
geo - 3 slice:
.1 10000
9999 - 10,000,000
9,999,999 10,000,000,000
or something like that.
By iterate I mean there's a loop, from 1 to n slices.
Before that loop I clear screen
And on each depth slice I clear depth buffer, and re-draw the whole scene
with a different depth slice / range
- working from far slice to near slice
So drawing can be slower by up to 3 times(although not quite - routing/node
compiling done once per frame). But no tearing from lack of depth buffer
depth. (might have tearing from float coordinate precision issues).
Its debatable - others say if you're careful one 24bit depth buffer should
be sufficient. Myself - I'm too impatient to try tuning or on-the-fly
direction-based range adjustments as the avatar is moving.
-Doug
<< WEB3D SPEC COMMENT RULES APPLY
On Fri, Jul 20, 2018 at 11:07 AM, Don Brutzman <brutzman at nps.edu> wrote:
> Attendees: John Carlson, Anita Havele, Vince Marchetti, Nicholas Polys,
> Dick Puk, Don Brutzman
>
> =================================
>
> 1. *Near and far clipping planes*. Initial discussion of a new possibility.
>
> Interesting review of OrthoViewpoint by Design Printing and Scanning
> Working Group in reviewing/resolving:
>
> Clarify ambiguous functional specification for OrthoViewpoint
> http://www.web3d.org/member-only/mantis/view.php?id=1238
>
> Relevant reference from OpenGL:
>
> glOrtho — multiply the current matrix with an orthographic matrix
> https://www.khronos.org/registry/OpenGL-Refpages/es1.1/
> xhtml/glOrtho.xml
>
> A long-term point of awkwardness in X3D (dating all the way back to
> VRML97) is author setting of near and far clipping planes. These fields
> are exposed via NavigationInfo, which is bound independently from
> Viewpoint/OrthoViewpoint/GeoViewpoint. Thus it is difficult to "get"
> current NavInfo to modify values. Further, the near clipping plane is
> first value of a triple, making any modification require elaborate
> node-discovery and then elabobrate scripting.
>
> X3D Tooltips: NavigationInfo avatarSize,visibilityLimit
> http://www.web3d.org/x3d/tooltips/X3dTooltips.html#Navigatio
> nInfo.avatarSize
> http://www.web3d.org/x3d/tooltips/X3dTooltips.html#Navigatio
> nInfo.visibilityLimit
>
> Here is a thought: if we add something like
>
> X3DViewpointNode : X3DBindableNode {
>
> SFVec3f [in,out] nearClippingPlane -1 with range -1, [0,infinity]
> SFVec3f [in,out] farClippingPlane -1 with range -1, [0,infinity]
> }
> http://www.web3d.org/documents/specifications/19775-1/V3.3/
> Part01/components/navigation.html#X3DViewpointNode
>
> then authors could easily/optionally provide context-sensitive clipping as
> part of any viewpoint. Backwards compatibility not a problem: illegal
> sentinel value of -1 for range from viewer indicates that current
> NavigationInfo settings prevail.
>
> This is very important in geospatial models with terrain, where
> anti-aliasing is a common problem. From prior tooltips:
>
> Warning: important design thumbrule is to keep (visibilityLimit /
> avatarSize.CollisionDistance) < 10,000
> to avoid aliasing artifacts (i.e. polygon "tearing").
>
> Thanks for discussion today, comments welcome. Expect a future Mantis
> issue here for further consideration.
>
> =================================
>
> 2. *Python language binding*. Thanks to John Carlson for his extensive
> work and for joining us today.
>
> a. First we created a new wiki page similar to
>
> X3D JSON Encoding
>
> If you go to the top of the following page
>
> Web3D Public Wiki
> http://www.web3d.org/wiki/index.php/Main_Page
>
> then scroll to the very bottom, you see a link
>
> Create New Page
> http://www.web3d.org/wiki/index.php/Create_New_Page
>
> which says
> ==========
> Do a search for an article page that doesn't exist.
>
> Click on the "this exact title" link at the top of the page.
>
> You will see a big white space to type in it.
>
> Click the "Save page" button... and voila. You've created a new article
> page!
> ==========
>
> So we did. There is now a new page
>
> X3D Python Language Binding
> http://www.web3d.org/wiki/index.php/X3D_Python_Language_Binding
>
> Initial contents that our discussion assembled are an impressive first
> pass:
>
> Motivation
>>
>> Why:
>>
>> multiple language bindings provide equivalent implementations of X3D
>> Scene Access Interface (SAI) Specification, which in turn accesses the X3D
>> Architecture Specification
>> Python is widely used, so many tools and applications might then
>> easily create/use/produce X3D
>> We are not afraid of programming languages that depend on whitespace!
>>
>> The X3D Specification Relationships diagram shows how the various
>> programming-language bindings and file encodings are related.
>> Resources
>>
>> Python script interfaces
>> H3D
>> Blender has an independent interface
>> NIH has written a series of Python scripts that exercise Blender
>> pyOCC python interface to Open Cascasde geometry kernel
>>
>> John Carlson has produced
>>
>> https://github.com/coderextreme/pythonSAI
>>
>> Deliverables
>>
>> Draft 19777-6 specification added in GitHub
>> Follow examples of other X3D language bindings
>> Reach proof-of-capability initial draft
>> New Work Item Proposal (NWIP) by Web3D Consortium for ISO
>>
>> Example scenes
>> Test scenes to demonstrate design patterns
>>
>> Implementations
>> Conversion stylesheet, X3dToPython.xslt
>> PyJnius cross-compilation conversion of X3DJSAIL java classes
>> Possibly another library, X3DPSAIL or X3DPYSAIL perhaps?
>>
>> Validation by compilation
>> are special tests needed, written in Python, to test program
>> validity?
>> Compatible with X3D Unified Object Model (X3DUOM)
>>
>> Plan of Action Milestones (POAM)
>>
>> TBD
>>
>> To Be Determined:
>>
>> Is it possible to run Python scripts in a Web browser?
>> Python support for DOM?
>> Masaki Aono produced some speculative code a few years ago
>>
>
> (Lots) more to follow. We will be having fun with X3D Python!
>
> =================================
>
> 3. *Medical*
>
> DICOM discussion on medical mailing list. Still working to get X3D added
> with STL.
>
> Vince and Nicholas and Anita are tracking/leading this. Dialog is on the
> medical working group list.
>
> Working group leadership opportunities are available for Web3D Consortium
> members.
>
> http://www.web3d.org/working-groups/medical
>
> Many crucial partnerships emerging, including HL7 and coordination with
> HAnim for medical records.
>
> =================================
>
> 4.ISO Meeting Preparations.
>
> Dick and Don will be attending annual meeting of our ISO Standards
> Committee (SC) 14 in Toulouse France, 6-10 August 2018.
>
> a. HAnim Draft International Specification (DIS) parts 1 and 2, including
> Motion Animation.
> b.X3D topics include annual summary, recent NWIPs for C C++ C#, planned
> work for the coming year in X3Dv4, JSON Python and Java.
> c. Collaboration of Design Printing Scanning Working Group in SC4 STEP
> with SC24 in Joint Working Group on CAD Presentation.
> d. InterestingISO efforts for 3D Printing and Scanning interoperability,
> Smart Cities.
> e. Review of Web3D Consortium specification process and Class A Liaison
> relationship with ISO.
>
> ================================
>
> 5. SIGGRAPH Preparations.
>
> Anita Nicholas and Don will be attending SIGGRAPH in Vancouver Canada,
> 12-16 August.
>
> http://www.web3d.org/event/siggraph-2018
>
> We will have several Birds of a Feather (BoF) sessions.
> https://s2018.siggraph.org/conference/conference-overview/
> birds-of-a-feather
>
> * ACM SIGGRAPH Cartographic Visualization (Carto) Birds of a Feather
> (Polys 3D Blacksburg Urban Planning, Brutzman SPIDERS3D)
> Monday, 13 August 2018, 12pm - 1:30pm
> ACM SIGGRAPH Theater, West Building, Room 102, Vancouver Convention
> Centre
>
> * Web3D Korea Chapter Standardization Meeting
> Monday, 13 August 2018, 3pm - 5pm
> Gallery Board Room, Pan Pacific Hotel
>
> * Design Printing and Scanning: Web3D Makers Making More!
> Wednesday, 15 August 2018, 11am - 12:30pm
> West Building, Room 116-117, Vancouver Convention Centre
>
> * WebVR Evolution for a Larger Web
> Wednesday, 15 August 201812:30pm - 2pm
> West Building, Room 116-117, Vancouver Convention Centre
>
> * Immersive Media BOF (Nicholas presenting multiple VT applications)
> Wednesday, 15 August 2018, 11am - 12pm
> East Building, Room 12, Vancouver Convention Centre
>
> ================================
>
> 6. Meeting plans.
>
> Monday 23 July: Communications Team updating public messaging.
>
> Friday 27 July: second pass on Python language binding, technical issues
> review.
>
> Friday 3 August: no meeting (Don and Dick en route).
>
> Friday 10 August: no meeting (ISO meeting conclusion).
>
> Friday 17 August: post-SIGGRAPH initial discussion, list of new technical
> issues from conference.
>
> As ever, member teleconference information is at
>
> Web3D Teleconference Information
> http://www.web3d.org/member/teleconference-information
>
> If someone needs to join as an invited expert for some call(s), please
> just ask to get the connection information.
>
> If you want to join Web3D Consortium and support these important efforts,
> please do. You can have excellent influence in support of your interests.
>
> Join the Web3D Consortium
> http://www.web3d.org/join
>
> Comments and feedback are always welcome, this is how we all progress
> together.
>
> Thanks everyone for another superb meeting today. 8)
>
> Have fun with X3D!
>
> 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/brutzma
> n
>
>
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