Geometry and Mesh - lorentzo/IntroductionToComputerGraphics GitHub Wiki

Triangulated mesh

• Triangle as rendering primitive (but not necessary modeling primitive)
  • Why triangles? Good discussion: https://www.youtube.com/watch?v=CoGo_3C7xR0&t=11703s&ab_channel=High-PerformanceGraphics
• geometry (shape): https://www.scratchapixel.com/lessons/mathematics-physics-for-computer-graphics/geometry /courses/the-pbr-guide-part-1)

Model in 3D scene:

• storage size
• render efficiency
• quality

Mesh representation:

• accuracy
• speed

Mesh can be available in different forms and must be transformed to tractable primitive: triangle

• tessellation

Sources of 3D data:

• procedural modeling: programs that create geometry
• transforming data into surface/volume (protein data to spheres)
• modeling programs: hard-surface, organic modeling, sculpting
• reconstruction: photogrammetry
• Sampling a real model using 3D scanner: points
• Isosurface from CAT or MRI
• modeling: manual modeling using DCC tools, procedural modeling, hybrid of manual and procedural modeling
• hard-surface modeling: rigid bodies such as cars, buildings, etc.
• organic-surface modeling: soft-bodies such as vegetation
• volume modeling: clouds, seas
• VFX (particles)
• simulation: algorithm which simulates certain phenomena (e.g., fluid simulation -> river stream or clouds formation)
• real-world capturing: photogrammetry, CT, point-clouds
  • https://alicevision.org/
  • https://www.matthewtancik.com/nerf

Solid vs surface vs implicit modeling:

• solid modeling: CAD; corresponding to actual machining processes: cutting, drilling, planning
  • Faceters: for display and analysis
• Surface modeling: Blender or Maya; not based around concept of solidity - surface modeling
  • curves and subdivision surfaces manipulation
  • mesh maniplulation
• implicit modeling:
  • SDFs; CSG
• Pointclouds
  • storage and reconstructing meshes

Important: understand how the data was created and for what purpose

• sometimes generated data is not suitable for efficient graphical display

Storing and transporting 3D data

3D data file formats

• OBJ
• GLTF
• FBX

Subdivision surfaces and displacement

• Loop subdivisions
• Catmull clack subdivision
• Displacement

Literature:

• RTR ch 16 and 17