The document discusses the process of converting large CAD assemblies into real-time 3D visualizations using Pixyz software, focusing on the challenges and solutions associated with CAD data treatment. It details methods for optimizing geometry, mesh generation, and scene tree management to enhance visualization quality while maintaining performance. Key steps include CAD surface repair, tessellation, mesh optimization, and integration with platforms like Unity for immersive experiences.

2. Turning Large CAD Assemblies
into Real-Time 3D Visualizations
PiXYZ Software | Cédric Rousteau & Axel Jacquet

3. UNLOCK CAD DATA FOR
REAL-TIME 3D EXPERIENCES
First-class algorithms for automatic CAD/DCC data treatment
What is PiXYZ?
polygon model
scan metadata
nurbs data
VR
Training, Simulation,
Product Viz, …
AR
Process Validation,
product viz,
marketing
MOBILE
Entertainment
Marketing, Sales,
Product Viz,…
WEB
Entertainment
Marketing, Sales,
Product Viz,…
GAME & VFX
Entertainment,
Simulations,
Visualization,…
ANY
DEVICE
ANY
USECASE

4. VRED to Unity workflow example
LINK

5. Why is it a challenge to bring CAD assemblies
in real-time 3D experiences?
EXACT MATHEMATICAL GEOMETRIES
BOUNDERY REPRESENTATIONS
DESIGN PRODUCT STRUCTURE
METADATA
SIMPLIFIED HIERARCHY | ASSEMBLY
OPTIMIZED MESH
REAL-TIME ANIMATION
PRODUCT MODELING
INFORMATION PHYSICS PROPERTY
MATERIALS
LARGE ASSEMBLIES
MATERIALS | UVs

6. • Many file formats
CAD Import
JT
STEP
IGES
IFC

7. CAD Import
• Complex and heavy product structure
Root
Rear Right
Wheel
Rear Left
Wheel
Rear Axle
Right Wheel
Left Wheel
Axle
Wheel
Front Right
Wheel
Front Left
Wheel
Front Axle

8. • B-Rep Topology structure
• 20 curve types
• 22 surface types
CAD Import

9. 1. Geometric optimization
2. Scene tree optimization
3. Meshes beautification
4. LODs
Autodesk Alias to real-time 3D use case
NURBS
CAD Data

10. Alias Model Analysis
Scene Tree
• Hierarchy levels
• Number of parts
• Naming
• Instances
• Empty nodes
• Variants
• Pivot points
BRep / Mesh Information
Material Information
Metadata

11. Geometric optimization
Scene tree optimization
Mesh beautification
LOD

12. Step 1/11
Repairing CAD surfaces
Inner free boundaries should be repaired (meaning stitched) prior to tessellation to create a beautiful, watertight mesh
Repair CAD

13. Repair CAD algorithm
• Sew face boundaries
No CAD repair prior to tessellation = Gaps in the meshes

14. Repair CAD algorithm
• Sew face boundaries
• Remove duplicated faces
No CAD repair prior to tessellation = non-manifold edges / duplicated polygons / Z-fighting

15. Repair CAD algorithm
• Sew face boundaries
• Remove duplicated faces
• Optimize loops
Without loop optimization With loop optimization

16. Step 2/11
Tessellation
Generate mesh well balanced between quality and density
1 875 352 tris

17. Tessellation algorithm
• Driven by criteria
• Max Sag
Sag = 0,1mm
Sag = 0,2mm
Radius=100mm Radius=50mm

18. Tessellation algorithm
• Driven by criteria
• Max Sag
• Max Angle
Angle = 10°
Radius=100mm Radius=50mm
Angle = 20°

19. Tessellation algorithm
• Driven by criteria
• Max Sag
• Max Angle
• Max Length
Length = 10mm
Radius=100mm Radius=50mm
Length = 30mm
∞
5
2
10

20. Tessellation algorithm
• Driven by criteria (Sag, Angle, Length)
• Based on fast and robust CAD modeler

21. Tessellation algorithm
• Driven by criteria (Sag, Angle, Length)
• Based on fast and robust CAD modeler
• Alignment of vertices over surfaces
Without alignment With alignment

22. Step 3/11
Repair Meshes

23. Repair Mesh algorithm
• Repair connectivity
• Merge coincident vertices

24. Repair Mesh algorithm
• Repair connectivity
• Merge coincident vertices
• Sew mesh boundaries

25. Repair Mesh algorithm
• Repair connectivity
• Merge coincident vertices
• Sew mesh boundaries

26. Repair Mesh algorithm
• Repair connectivity
• Merge coincident vertices
• Sew mesh boundaries
• Orient consistently
• Propagation

27. Repair Mesh algorithm
• Repair connectivity
• Merge coincident vertices
• Sew mesh boundaries
• Orient consistently
• Propagation
• Split Môbius strips

28. Step 4/11
Fix faces orientation

29. Smart Orient algorithm

30. Smart Hidden Removal
Remove hidden entities (parts, patches, polygons) using cavities automatic identification

31. Geometric optimization
Scene tree optimization
Mesh beautification
LOD

32. Step 5/11
Optimize scene tree

33. Step 6/11
Adjust pivot points of moving parts

34. Geometric optimization
Scene tree optimization
Mesh beautification
LOD

35. Step 7/11
Generate UVs & Assign material names

36. UV Generation
• From CAD Faces
• Surface parameterization
• Uniform parameterization
• By projection
o Box
o Spherical
o Cylindrical
• Automatic unwrap (beta)
→ Find the best lines to cut the mesh
→ Control angle and area deformation

37. Repack UV

38. Geometric optimization
Scene tree optimization
Mesh beautification
LODs

39. Step 8/11
Export LOD 0
1 875 352 tris

40. Step 9/11
Decimate with quality control for LOD 1
1 875 352 tris 914 905 tris
LOD0
LOD1

41. Decimation Algorithms
• Quality driven
o Vertex removal
o Maximum deviation
o Normal distorsion control
o UV Distorsion control
With normal control
Without normal control

42. Decimation Algorithms
• Polygon target
o Edge collapse
o Quadric Error Metric
o Mesh attributes preserved
100 000
10 000
1 000

43. Step 10/11
Decimate with polygon target for LOD 2
148 494 tris

44. Step 11/11
Shadow & Physics proxy meshes
5 504 tris

45. Proxy Generation
Proxy Mesh Voxelize Marching Cube

46. Baked Proxy Generation
Baked PBR maps
Original Model
40k triangles
3 materials
2 meshes
Baked Model
8k triangles
1 material
1 mesh

47. Import in Unity…
Mesh
Metadata
Product Structure
Material Assignment
via Rule Engine
*.pxz file
Credits: Unity Technologies

48. … and create great Real-time experiences
Credits: Unity Technologies
LINK

49. CAD DATA
CATIA, SIEMENS NX,
ALIAS, …
MESH &
3D SCAN
METADATA
COLOR, MATERIAL,
TEXTURE, NAME
PLM
DATA
Data Prep automation

50. What’s next?
Machine Learning

51. Thank you