3D Diff: An Interactive Approach to Mesh Differencing and C - PowerPoint Presentation

Slide1
Slide2

3D Diff: An Interactive Approach to Mesh Differencing and Conflict Resolution

Jozef

Dobo

š

and Anthony Steed Slide3

Case StudySlide4

Case StudySlide5

Case StudySlide6

Case Study

?Slide7

Case StudySlide8

Motivations

Scene might be edited concurrently

3D differencing and merging is tedious manual work

Editing software such as Max, Blender do not aid the merging process

Textual changes unlikely to work

Most of the time entire edits from one version

Various modes of interaction and visualization possibleSlide9

Contributions

Definition analogous to software merging

Automatically detect

differences

Provide interactive

ways for merging

Distinction of conflicts

Explicit:

components edited concurrently

Implicit:

caused by side-effects of merging

Prototype open source tool (

3D Diff

)

Evaluation of different visualizations with usersSlide10

Previous Work

Asset management and version control

VisTrails

Provenance Explorer for Maya

[

Bavoil

et al. ‘05]

Non-linear Revision

C

ontrol for Images

[Chen et al. ‘11]

3D Revision Control Framework

[

Dobo

š

& Steed ‘12

]

High-end CAD packages

Model correspondences

Contextual

Part Analogies

in 3D Objects [

Shapira

et al. ‘10]

Exploring Shape Variations by 3D-model Decomposition and Part-based Recombination

[Jain et al. ‘12]Slide11

Software Merging

Versioning

Pessimistic: locking

Optimistic: merging

Merging support

State-based (only

state at the time of

merging)

Change-based (all

individual

changes)

Operation-based (changes

re-run in

editor)

Visualization strategies

[

Gleicher

et al. ‘11]

Juxtaposition (side-by-side)

Superposition (overlay)

Explicit encodings (time warp/

substractions

)Slide12

Our Method

Stages

Automated

3D differencing

Interactive

3D

merging

Input

Two

3D models

Optionally their ancestor (resolves ambiguities)

Output

Merged 3D model

Direct conflicts to be resolved in a vertex-level editorSlide13

Processing PipelineSlide14

Processing Pipeline

Start from a common 3D sceneSlide15

Processing Pipeline

Modify independentlySlide16

Processing Pipeline

Export as filesSlide17

Processing Pipeline

Load into our tool and automatically diff (2-way)Slide18

Processing Pipeline

Optionally add common ancestor (3-way)Slide19

Processing Pipeline

Interactively mergeSlide20

Processing Pipeline

Export as fileSlide21

Representation

3

D

model as a generic scene graph

Directed acyclic graph

Edges carry no information apart from parenting

Every component is a node (incl. transformations, meshes…)

Smallest unit of change is a node

Corresponding nodes have matching IDs

[

Dobo

š

& Steed ‘12]

Changes tracked:

addition, deletion, modification

If a node is changed, all instances are affected

Graph topologies can be differentSlide22

Conflicts

Explicit conflict (direct)

Node exists in both models and is not

equal

Equality is implementation

dependent

Implicit conflict (indirect)

Semantics are violated

Bounding box intersections introduced during the merge processSlide23

3D DifferencingSlide24

3D DifferencingSlide25

3D DifferencingSlide26

3D DifferencingSlide27

3D DifferencingSlide28

3D DifferencingSlide29

3D DifferencingSlide30

3D DifferencingSlide31

3D Merging

Aims

to build syntactically

correct

model

Joins resolved and conflicted nodes

Partial automation

Added

Deleted

Modified

Ambiguities resolved manually

Added/deleted

Deleted/modified

Explicit conflictsSlide32

Implementation

Independent from modeling tools

C++ and Qt

Open Asset Import Library (

Assimp

)

Currently

only meshes, extensible to other components

Performs in-memory byte-by-byte comparison on

Vertices

Indices

NormalsSlide33

Visualization

Same UI for 2-way and 3-way differencing

Modes

Overlay (merge window only)

Standard (two differenced models + larger merge window)

Smart (standard + indirect conflict detection)

Differences shown as

Color coded highlights

Table with tick boxes

Scene navigation linked across windows

Automated

cameraSlide34

2-way DiffSlide35

2-way Overlay Slide36

2-way StandardSlide37

3-way DiffSlide38

3-way DiffSlide39

3-way DiffSlide40

User Study

3D merging with increasing level of support

Two-way overlay

Two-way standard

Three-way standard

Three-way smart

8 PhD students merged 4 sets of modified models

Sample model

Small industrial model

Large city model

Tests and model sets shuffled according to Latin squareSlide41

Evaluation

Questionnaire after each test

Participants

Able to explore options easily

Varied in judgement of merge success

Indirect conflict detection considered usefulSlide42

Conclusions

Problems of 3D differencing and merging are identified

Scene graph abstraction provides syntactically and semantically correct results

Node-to-node correspondence is assumed

Indirect conflict is regarded as a violation of semantics

Interactive prototype tool visualizes both types of differencingSlide43

Future Work

Correspondences to be resolved

Granularity of changes might not fit all projects

Differences on vertex-level to be detected

Intentions could be automatically inferredSlide44

References

Bavoil

,

L.,

Callahan,

S. P.,

Crossno

,

P. J.,

Freire, J., & Vo, H. T. 2005. Vistrails: Enabling interactive multiple-view visualizations. In IEEE Visualization 2005,

135–142

Chen,

H.-T.,

Wei,

L.-Y.,

& Chang,

C.-F. 2011.

Nonlinear revision

control for images. ACM Trans. Graph. 30, 4 (Aug.)Dobo

š, J. & Steed, A. 2012. 3d revision control framework.

In Proceedings of Web3D ’12, ACM, 121–129Gleicher, M., Albers, D., Walker, R.,

Jusufi, I., Hansen, C. D., & Roberts, J. C. 2011. Visual comparison for information visualization. Information Visualization

10, 4 (Oct.)Jain, A., Thormählen, T., Ritschel, T.,

& Seidel,

H.-

P. 2012

. Exploring shape variations by 3d-model

decomposition and

part-based recombination. Comp. Graph. Forum (Proc.

Eurographics

2012

) 31,

2

Shapira

,

L.,

Shalom,

S.,

Shamir,

A.,

Cohen-Or,

D.,

& Zhang,

H. 2010. Contextual part analogies in 3d objects.

Int.

J

. Comput. Vision 89, 2-3 (Sept.), 309–326Slide45

Sponsors

Arup Foresight

http://

driversofchange.com

UK Engineering and Physical Sciences Research Council

http://www.epsrc.ac.uk

UCL Engineering Doctorate Centre in Virtual Environments, Imaging &

Visualisation

http://engdveiv.cs.ucl.ac.ukSlide46

3drepo.orgSlide47

Visualizing 3D Models in Aid of Public Consultation

Saturday

11:00 -

12:45, Tourmaline 207Slide48

VideoSlide49