houdini tutorial database

Debris Systems

Debris Systems

cmiVFX has released Houdini Debris System. One key to a believable destruction effect is the complexity of the bits and pieces. Modern films push the limits of technology every summer with flying debris. Modeling, placing, and keyframing such a mess is simply not possible. Okay then mathematics leveraged to create the chaos of a falling building is great in theory, but how does one control that chaos short of a phd? Suppose one does get a reasonable debris sequence out, but the director wants a bit more motion blur and "Oh, how about a more rocks and have them shoot over to the right... just a tad". Alvaro Segura with cmiVFX is here to answer all those situations and more with this amazing, brain melting courseware. Whether you are already in the celluloid trenches or you aspire to be, THIS LESSON IS A MUST.

Short Description
Cracking and crushing a model is only a part of a cinematic destruction sequence. Visual effects professionals in the trenches know that a solid DEBRIS SYSTEM is also a necessary piece of the puzzle. Alvaro Segura here now reveals one way to create debris that is re-usable, direct-able, and production ready

Chapter 1 - Introduction

Chapter 2 - Creating The Debris Library

We start by creating a procedural library of debris geometry based on Voronoi fracturing and using color attributes to shape the geometry. This library is re-usable and fully able to handle all manner of 'debris'. This lesson uses rocks, but the library could just as easily be stocked full of window frames, glass shards, and skyscraper furniture. We will then come up to a useful trick to export our set of debris geometry and use it later for our debris generator setup.

Chapter 3 - Basis For Debris System

Here we setup the basis for the debris system. At its most basic proof of concept degree, this is merely a way to identify and visualize the attributes needed in the much more complex system to come.

Chapter 4 - Marry Dots and Rocks

Lets begin to bring in the items from our library. Keystone in this chapter are a wicked long expression and a very clever way to limit velocity. Our level of control increases quite alot with some very simple use of groups.

Chapter 5 - Adding Rotation

This chapter is all about adding spin to our particles which in turn will make the motion of the debris more believable. The way it is done though will be new to all but the most advanced users. The rotation is driven by a rotation pop, forces and expressions. Refining the realism and illusion of chaos by adding rotation behaviors based on collisions, altering the rotation speeds and direction after hitting on collisions.

Chapter 6 - Painting Destruction

This chapter begins with a quick revision to the debris system by refining the particles a bit (part A). Lets now visit TurboSquid.com for a nice choice of free models to destroy. After some cleanup it is time to paint the blood of impending doom where the fissures will be seeded (part B).

Chapter 7 - A Bad Place To Park

Okay, lets blow this joint. Nothing is more fun than a giant ball of string that crushes everything in its path. (Well, okay a few things are more fun...) Everything has led up to the point at which the debris system has something to emit from. Now our scene is applied to the Rigid Body Dynamics features of Houdini where Alvaro makes use of the NEW Bullet Solver in Houdini 12.

Chapter 8 - Re-Timing - Sloooooo-Mo

To add a sense of large scale, one can slow down the action. This simple technique retimes the collapsing building and thereby adds to the illusion of a multi-story structure rather than a toy.

Chapter 9 - Adapting Our Debris System

While the debris system was functioning, there is room to make it better. This chapter refines the system to fit the collapsing destruction. Triggers and timing are setup to integrate the debris with the destruction. Triggering tricks using simple expressions are a bit of wizardry that allow the VFX TD to control when and where the magic happens.

Chapter 10 - Reconnecting Collisions

The debris must interact with our scene dynamically. Keep in mind that the particles are what are actually colliding. Creating relationships between the debris particles and the scene geometry is our focus.

Chapter 11 - Tweaking and Enhancing

Finally, after a series of tests you will see how to fine tune and finalize the scene. This short troubleshooting and cleanup sequence will help you complete your own scenes in the future.

Chapter 12 - Velocity Blur and Rendering

This modest courseware is wrapped with with some basic lighting involving Ambient Occlusion to show the power of our Debris generator setup along with velocity blur. As a debris TD it is often necessary to demonstrate your scene with some basic shading and lighting. This final chapter wraps up the lesson with some ambient occlusion for lighting.