1. Real-time Procedural Volumetric Fire
Alfred R. Fuller, Hari Krishnan, Karim Mahrous, Bernd Hamann, and Kenneth I. Joy
Institute for Data Analysis and Visualization, University of California, Davis
The method presented uses hardware acceleration, a realistic particle simulation and “Improved Perlin Noise” to create real-time procedural volumetric fire that supports macro-scale bi-directional environmental interactivity. The fire’s shape and color is modified via a two-dimensional fire profile texture. The motion of the fire can be pre-animated for scripted events or interactively generated by the particle simulation. The method creates visually convincing real-time three-dimensional fire, without the artifacts commonly seen in sprite systems or the computational costs associated with true photo-realistic fire simulation and rendering.
Introduction
Methods
Fire in three-dimensional environments has classically been generated using a set of fixed-resolution two-dimensional sprites with static animation.
– Volumetric fire provides a true three-dimensional representation.
– Improved Perlin Noise supports unique dynamically animated fire generation.
– Free-form volumetric deformation provides the flexibility needed to support smooth bi-directional environmental macro interaction.
Central Spline and Lattice Construction
The lattice surrounding the fire is extremely flexible while maintaining texture coordinates for easy rendering. Four corner splines are generated having a distance of XXXX units away from the center spline. The center spline is sampled by length to find the associated position on the corner splines. This produces both the positions and texture coordinates of each corner in our lattice.
Lattice Slicing
Once the lattice is constructed an optimized cube “slicer” is used to generate evenly spaced view-aligned planar quadrilaterals that maintain the associated texture coordinates. A pixel shader is used to render the quadrilaterals.
Discussion
The macro shape and perceived burning speed can be controlled by a realistic particle simulation that takes into account wind, movement, macro collisions, high-energy particle dispersion, and thermal buoyancy.
Volume Generation and Deformation
The provided fire profile texture is swept around the y-axis to create a “unit” fire volume. When rendered on the lattice slices, this unit fire volume is appropriately deformed along the center spline. This step accounts for all macro changes in shape and size.
The system supports easy modification of the shape and color of the fire through the manipulation of a two-dimensional fire profile texture. The fire’s macro movements can be pre-scripted for a deterministic sequence of events.
Fire Shader with Improved Perlin Noise
Improved Perlin Noise is used to animate the micro details of the fire. The level of detail of the Improved Perlin Noise is scaled to world coordinates in the pixel shader to eliminate stretching and scaling artifacts. Additionally, the perceived burning speed of the fire can be passed as a parameter to the pixel shader.