A Data-driven Approach for Synthesizing High-resolution Animation of Fire

Syuhei SatoTakuya Morita

Yoshinori DobashiTsuyoshi Yamamoto

Hokkaido University

DigiPro '12 Proceedings of the Digital Production Symposium

Introduction

• Animators try to create the desired motions by repeating fluid simulations with different parameters until a satisfactory result is obtained.– Expensive computational cost

Relative Work

• Control the fluid simulation to create the desired motion

• Covert the low resolution into high resolution• Control the high resolution with low resolution• Combining noise into low resolution

Less realistic than those obtained by physical simulations

Motivation

• Similar flow pattern at different times and positions on different scales during animations of gaseous objects.

• Preprocessing step: database of high-resolution velocity field(2D)

• High resolution velocity field is synthesized from the low resolution with linear combination of the precomputed velocity field.

Features• The database is created by 2D fluid simulation. We use 2D

velocity fields to add small-scale detail to the 3D low-resolution velocity field. This results in a significant reduction in computational costs for both precomputation and the run-time process.

• Using our synthesis method recursively, animations can ideally be synthesized with arbitrarily high resolution.

• The method is highly suitable for parallel computation. The low-resolution velocity field is subdivided into small blocks

and the high-resolution velocity field can be synthesized in parallel for each block.

Overview

Database Construction

• Constructed by 2D fluid simulation– Divide into nb X nb blocks– Apply PCA(principal component analysis) to get

PVF(principal velocity fields)• Cannot synthesize detailed turbulence in 3D

simulation if such turbulence is not included in 2D simulation.

Synthesizing a High-resolution 3D Velocity field

• A low resolution 3D fluid simulation is executed and converted into high resolution by PVF.

• Each output velocity is generated slice by slice and each slice is divided into blocks.– The blocks overlap in order to reduce the

discontinuity.

Converter

Compute the weight for PVF• Apply the above process three times: xyz – Horizontal component in 2D: u is used for horizontal

components in 3D: x, y– Vertical component in 2D:v is used for vertical components

in 3D: z• Solve three minimization problems

Recursive Synthesis

• The method fails when the resolution ratio is too high. From the experience, the ratio should less than 4

• Solution: vl(input) is converted to v1, then v1 is converted to v2…..

Results