Soft Body Simulation

What is Soft body? A soft body is basically an object which changes its overall shape due to external forces acting on it. Some examples that we commonly see include cloth, balloons and jelly.

Applications for soft body simulations:-

Computer Graphics (animation)

Virtual Reality

Games

And many more…

Existing Soft Body Models Spring-Mass based models

- easy implementation, weak results

FEM, FEV based techniques

- great results, complicated implementation, slow

Fluid based model

- good results, not for realtime

Purpose "...to create model which will be fast, easy in implementation and gives good soft bodies behavior."

Problem statement To design a plugin for Unity developers that helps in simulation of interactive soft body (Jell-O like) with spring mass and pressure model in Unity

To develop an AR based Android application to visualize this simulation.

This soft body can be any given mesh and/or parts of a given mesh.

We can merge different meshes also.

Spring Mass Pressure Model Spring :

Each edge of the mesh is converted into springs with a spring constant and a damping constant.

User can change these constants according to their needs.

Mass : Each vertex has a definite mass which can be

modified by the user. User can change Gravitational

force constant.

Pressure: Pressure is applied inside the mesh so that it

Can behave like a balloon. User can change Pressure constant.

Background of Pressure Model Create Spring Mass System

Create a simple cloth.

Apply wind force (left -> right)

We will see a deformation in the cloth.

Algorithm proposed Create closed shape of the cloth

And.. put "source of the wind" inside.

Wind Source?? Wind source basically provide a pressure to the mesh.

We can consider a gas which will provide the necessary pressure.

- We will put an ideal gas inside of the body

- And apply some basic physics to it.

Ideal Gas Approximation Pressure value is described by Ideal Gas Equation:

P V = nRT

P- pressure value

V- volume of the body

n- particles number

R- gas constant

T- gas temperature

Pressure Force calculation We can calculate pressure to a point with this equation:-

And for pressure:-

Assume n, R and T are constant. So we have to calculate the volume of the body.

Volume We use gauss theorem to calculate volume of the body.

Collision detection and response are also handled.

 If F is a continuously differentiable vector field defined on a neighborhood of V, then we have

The left side is a volume integral over the volume V, the right side is the surface integral over the boundary of the volume V.

Implementation

NoveltyThe diagram below compares the existing spring mass model with the new spring mass with pressure model.

AR based Android App - Uses Vuforia AR library.

- Designed to visualize soft body simulations of 3D figures from every angle and at every step of simulation.

- Start/Stop functionality.

Results

AR application

Conclusion Pressure Model of Soft Body behavior

it is fast.

gives good Soft behavior in real time.

it is easy for implementation.

Future Work Increase the performance of our algorithm to give better results in less amount of time.

Increase user interaction in the mobile app.

Design a mobile AR based game for better understanding of soft body for educational purposes.

Stabilize the system for inter-mesh collisions.

Collision with other rigid bodies and soft bodies would be incorporated.

Thank You..!!