Structural Modeling of Flames for a Production Environment

Eric Hielscher

CS 777

Reasons not to use a simulator

• Numerical simulations are computationally complex

• Multiple factors affect its appearance and thus lead to unintuitive control parameters

• Chaotic – small changes in initial conditions lead to dramatically different results and thus iterative methods are difficult

So… we cheat

• Instead of simulating real fire, we can use this paper’s method of breaking down how flames look into various things that “look good” even though they aren’t necessarily correct

System Components

• B-spline models flame’s structure

• A profile is used to create a volume to represent the oxidization region

• A flame image is sampled and mapped to the spline

• Top portion of flame can break away

• Procedural interface

B-spline – the curve’s spine

• First, the user creates a B-spline to model the height of the flame

• The B-spline’s control points convect within wind fields

• Curve is resampled parametrically to ensure that clustering of control points doesn’t lead to visual artifacts

Flame Profile

• A profile of a flame is selected from a library of them or drawn by hand

• This profile is rotated to create a volume of revolution in which the flame resides

Flame image sampling

• Next, a flame image is sampled and particles are created that match the image’s colors

• These particles are then cylindrically mapped to the B-spline

Separation

• Periodically, a random function is tested to decide whether the top portion of the flame separates

Procedural Interface

Various controls are presented to the user, including:

• Flame source image• B-spline modeling• Life span of separated plumes• Wind field controls• Interaction with other objects• Flame Spread

What I did

• Created B-spline

• Created volume from profile curve

• Sampled flame image

• Tried to cylindrically map particles to B-spline

Some shots

A source flame image A screenshot of aflame

What was hard

• Paper assumed lots of background knowledge and resources

• Some of that background was hard to find, other parts were too large/difficult to implement given the timeframe

• It never seemed to look right