Screen Space Animation of Fire

彬彬

Abstract

We present a simple and physically inspired method to animate realistically

looking fire directly in 2D instead of along a 3D simulation.

This naturally reduces the complexity of the animation from O(n3)

to O(n2). The fire is represented as a 2D scalar density field located

on a plane facing the camera, and is advected under a 2.5D velocity

field. In our method, the apparent motion of the fire on the viewing

axis is mimicked by introducing vibrations in the velocity field. We

model these rapid vibrations as pressure waves found in compressible

fluids and therefore consider the full Navier-Stokes equations.

The equations can be solved in a single pass and our method entirely

runs on the GPU. A natural extension is to make use of this

method directly in screen space: instead of filtering down the fire’s

simulation grid in world space, we rasterize the fire’s source, and

perform the simulation on a coarser grid directly in screen space.

The results are continuously renewed 3D-looking fires computed

solely in 2D.

1 Introduction

It was noted in [Horvath and Geiger 2009] that the motion of fire

on the viewing direction is less important than the motion spanning

the viewing plane. This observation led us to incorporate the motion

of the fire on the third dimensional axis into a visually compelling

2.5D velocity field. In a similar mindset, [Rasmussen et al. 2003]

obtained a three-dimensional incompressible flow by combining a

set of two-dimensional simulation grids along a Kolmogorov spectrum

turbulence model which provides coherence on the third dimension.

Our method keeps a two-dimensional representation for

the velocity, but attempts to consider the apparent motion of the fire

on the third dimensional axis directly into the 2D velocity field. We

do so by exaggerating the compressibility effects of a fluid in order

to create large pressure waves, which tend to break the flames during

advection and create the illusion of depth in the fire’s motion.

彬彬

彬彬

奇

再次路过……

C.R.CAN

有意思！学习了！

晃晃

凡系斑竹滴话要听；凡系朋友滴帖要顶

晃晃

好可爱的字,学习了

晃晃

呵呵，很好，方便罗。

tc

佩服，好多阿 ，哈哈

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