看不懂英文同學的可以用谷歌瀏覽器插件：騰訊翻譯

本文對應的是Houdini火焰模擬視頻教程：

https://www.bilibili.com/video/BV16V4y197Aj/?spm_id_from=333.999.0.0

After a call for an encore from fxphd members, Jonathan Gilbert returns for an intermediate level course covering Pyro FX in Houdini. Pyro FX can be a bit overwhelming when first starting out. This course will simplify and demystify the Pyro FX tools, ultimately giving you the skills needed to create just about any fire and smoke effect that you might need. Members will become familiar with Houdini’s Fireball, Billowy Smoke, Wispy Smoke and Flames Pyro FX shelf tools. These lay the groundwork for learning the basics of a Pyro simulation, these same tools can also over-complicate some of the learning. So we’ll simplify the simulation down to the very bare-bones. From there, we’ll build upon this foundation and achieve a full understanding how each parameter effects the simulation. We’ll explore how to define fluid properties such as viscosity, cooling rate and buoyancy.

Next, we’ll move on to controlling the behavior of the fluid. We’ll use Turbulence, add DOPs Forces and Motion FX to achieve much more interesting and artistically controlled fluid motion. Then we’ll use the Combustion model to ignite fuel and create fire and smoke. Next, we’ll take a journey into some of the more advanced topics such as creating a Pyro simulation from scratch, defining custom attributes, using custom velocity fields to direct fluid motion and modifying the fluid behavior with microsolvers. With this knowledge, members will be able to simulate almost any type of smoke and fire effect you can imagine.

At the end of the course, we’ll explore post processing our fields of data with the more recent volume tools in order to save re-simulating. We’ll setup some simple lighting to have a more accurate depiction of the fluid in the viewport and ultimately a much more beautiful render. Which leads us to an exploration of the Material Shader Builder and the Pyro Shader for shading our fluid. Finally, we’ll cover guidelines for efficiently and effectively rendering volumets with Mantra.

Professor Jonathan Gilbert is a freelance VFX artist with over six years of Houdini experience. He graduated with his MFA in 3D Animation and Visual Effects with a concentration in fluid dynamics from the Academy of Art University in San Francisco. He then worked at Side Effects Software Inc. building and teaching a series of basic and intermediate Pyro Effects classes in Santa Monica. His experience includes work at Asylum on the Black Eyed Peas Dirty Bit music video and more recently, on the last Harry Potter and the Deathly Hallows Part 2 as a Technical Director at Gradient Effects.

Class 1: In class 01 of the HOU204 Pyro FX course, we discuss the overall expectations and the level of experience necessary to get the most from the course. Afterwards, we take a brief tour of the the Fireball, Billowy Smoke, Wispy Smoke and Flames Pyro FX shelf tools, then use the Flames tool to setup a very simple Pyro simulation. We then use this to discuss some of the basics of volume-based fluids such as the fluid container, voxels, fields and solvers. We look at the basic dynamics network that was setup by the shelf tool which included a smoke object, pryo solver, source apply, gravity force and the up-res tools. Then we looked at a simple example of a 2d grid with an image applied to it and how at a low resolution, the image isn't very detailed or accurate but at a higher resolution it becomes much more detailed at accurate. We then apply this concept to a 3D volume and look at the concept of voxels and their importance in determining a high resolution and more accurate simulation versus a low voxel resolution simulation which will have less detailed and not as accurate fluid simulations. Finally we took a look at the DOP I/O SOP that is used to import field data from DOPs to be light, shaded and rendered. Which also led to a brief discussion on the Volume Visualization SOP that is used to modify the viewport representation of our field data. The rendered geometry however is set to the DOP I/O SOP which has a Pyro Shader applied to it, which will get used to shade the object to look like smoke and fire.

Class 2: Introduce the Pyro FX shelf tools. This includes the Fireball, Billowy Smoke, Wispy Smoke and Flames. Discuss in great detail the the Smoke Object, Pyro Solver and the Source Apply. Use the Smoke Object to define the fluid container, initial States, Wind Tunnel and Boundary conditions. Then use the custom visualization options to view the important fields. Discuss some conflicts between the Source Apply and the Pyro Solver’s Source emission parameters. Define an emission source and apply animated noise to it to get more interesting emission results. Investigate how Temperature effects buoyancy causing fluids to rise or fall.

Class 3: Simplify the Billowy Smoke simulation. Use this as a base to build upon to get a better understanding of how each parameter truly effects the Pyro simulation. Begin an in-depth look at the Pyro Solver. Start exploring the basic properties of the fluid such as viscosity, cooling rate and vortex confinement. Add turbulence to create more interesting motion in the smoke. Explore the difference between Seeding vorticles and using Vortex Confinement to introduce spinning swirly motion in the fluid. Then use diffusion to blur the temperature, density or fuel fields over time. Use Motion FX to add animated noise to the initial velocity of the smoke. Then discuss the use of the Forces parameters in the Pyro Solver for global scaling control over all forces in the Pyro simulation.

Class 4: The combustion model used for creating fire and smoke. This allows fuel to ignite and create fire. The burning can release heat, gas, soot and smoke. Use the Fireball and Flames tools to assist in the exploration. Compare the differences in the Pyro setup for smoke and fire. Explore how to catch dynamics objects on fire.

Class 5: Learn to paint attributes such as fuel and temperature in SOPs. Then use these attributes to drive a Pyro simulation. Afterwords take a quick look at how to use RBD objects to ignite fuel on fire.

Class 6: Explore how DOPs Forces can be used to effect the behavior of the Pyro simulation. We’ll discuss some of the more commonly used forces such as wind, uniform force, noise field, vortex and magnet. Look at how to setup a simple smoke stack effect.

Class 7: A brief tour of lighting, shading and rendering smoke and fire. This will include looking at the Material Shader Builder and the Pyro Shader. Then we’ll talk about guidelines for rendering volumetrics in Mantra to get an efficient and high quality result render.

Class 8: We’ll use the Pyro FX shelf tools to automatically setup a Pyro simulation with Up Res Pyro tools. Then we’ll have a brief discussion how to take the base simulation and upres it into a much higher resolution, more detailed looking pyro simulation.

Class 9: Custom velocity fields in SOPs to artistically direct the fluid motion in DOPs. We’ll look at multiple methods for creating the velocity fields and different ways to make use of this in DOPs. It will require a discussion and use of the Field Force, SOP Geometry, SOP Vector Field, Vector Field, Vector Field Visualization, Gas Particle to Field, Gas Calculate, Gas Diffuse and Gas Dissipate.

Class 10: All of the Pyro simulations were required to exist inside a pre-defined fluid container. In this final class, we’ll look at a method to automatically resize the fluid container so that the Pyro simulation can move freely anywhere in the scene. Next we’ll look at different methods for post-processing the simulation with Houdini’s volume tools. Artistically sculpting and manipulating the data without needing to re-simulate the entire simulation from scratch will be invaluable. With all of these tools, you should be able to quickly and effectively create whatever fluid effect you’ll want! Introduce the idea of burning a piece of paper. Setup an automatically resizing fluid container so that the Pyro simulation is free to move where it wants.