Soft body physics and fracture generation Erich Jagomgis What is - - PowerPoint PPT Presentation

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Soft body physics and fracture generation Erich Jagomgis What is - - PowerPoint PPT Presentation

Jun 12, 2023 568 likes •923 views

Soft body physics and fracture generation Erich Jagomgis What is a soft body? What is not a soft body Rigid body Fluid Particle system Soft body properties Deformable Retains original shape Expensive to

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Soft body physics and fracture generation

Erich Jagomägis

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What is a soft body?

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What is not a soft body

  • Rigid body
  • Fluid
  • Particle system
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Soft body properties

  • Deformable
  • Retains original shape
  • Expensive to compute!
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Types of soft bodies

  • Rope (1D)
  • Cloth (2D)
  • Object (3D)

Examples

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Example

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So… How do they work?

  • Dark Magic
  • Sacrifices of innocent souls
  • <Insert mom joke here>
  • Mathematician tears
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Models

  • Spring-mass model
  • Finite element simulation
  • Shape matching
  • .. apparently many others.
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Whatever model works on principle

  • A set of constraints- a equation system for each point
  • A solver that iterates until constraints are satisfied
  • A lot of parameters

○ For material ○ For solver

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Lets focus on spring/mass model

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Lets focus on spring/mass model Point

  • Mass
  • Position
  • Metadata (eg. previous position)
  • Velocity
  • Inertia
  • Angular Velocity
  • ...and much more
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Lets focus on spring/mass model Spring

  • Rest length
  • Min length
  • Max length
  • Force
  • Dampening
  • Stiffness
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Lets focus on spring/mass model

Example 1 Example 2 Example 3

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Spring/Mass model issues

  • How do you structure the object?
  • Issues with collision detection

VS

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Example of exhaustive approach

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Achiements

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Nvidia Flex

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Fracture generation

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Fracturing models

  • Premade fractured model
  • Fracture mapping
  • Real-time fracture generation

○ Scientifically plausible ○ Rough approximation

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Premade fractured model

  • Object comes as a collection of fractured pieces
  • Pieces are glued together
  • More mesh for graphics component to handle
  • Less data needed for physics simulation
  • Either ignore or take take into account point of impact
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Fracture mapping

  • Model comes with a fracture mapping
  • Upon impact, fracture mapping is used to decompose object
  • Most commonly used

○ Blender ○ Apex library ○ Unity

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Fracture mapping

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Real time fracture generation

  • Ignoring point of impact vs taking it into account
  • Some algorithm is used to iteratively generate fractures
  • Most computationally expensive
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Real time fracture generation: Voronoi

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Another example

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Real time fracture refinement

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Real time fracture refinement

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A cool approach

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Another cool approach

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Another cool approach (2)

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Another cool approach: Result

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Boiling it down

  • Detect impact
  • Figure out how to fracture (mapping or some algorithm)
  • Use fractures to split mesh into parts
  • Add the parts to the scene
  • Calculate velocities, inertia, mass etc.
  • Do it in a single render cycle or several.
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Cluster Trucks

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Discussion