Brian Bunch Christensen – Visual Computing Lab

Procedural Cellular Modeling

Brian Bunch Christensen — Thu, 13 Feb 2014 10:04:56 +0000

Inspired by the Elementacular project, we’ve been working with the animation and illustration company Mediafarm to develop a similar procedural method for designing cellular and organic surfaces. The method uses hardware tessellation to displace an input surface in the normal direction. The displacement is specified using displacement curves combined with a number of “cell types” which define a certain look. Here’s a before-and-after shot of our cellular material:

Here’s another couple of examples, which show that we can apply our material to various shapes and are able to discard part of the output geometry based on a displacement threshold:

Educational Augmented Reality Prototype

Brian Bunch Christensen — Tue, 17 Dec 2013 12:27:18 +0000

In collaboration with VIA University College, we’ve recently completed a quick prototype of an educational iPad app for hospital nurses. It is an augmented reality app (built in Unity) which overlays a t-shirt logo with a pair of lungs that undergo a respiratory cyclus. The lungs are placed as though they are actually inside the person wearing the t-shirt.

Going to SIGGRAPH in Los Angeles

Brian Bunch Christensen — Mon, 30 Jul 2012 08:46:25 +0000

Five of us are going to SIGGRAPH in Los Angeles next week. We are very excited and look forward to a week of interesting papers, presentations and discussions. If you want to meet up with us, send an e-mail to $$mathrm{brian.bunch @ alexandra.dk}$$

Paper Accepted for SCA 2012

Brian Bunch Christensen — Fri, 06 Jul 2012 11:32:07 +0000

Our paper on simulation of immiscible fluids on unstructured meshes was recently accepted for publication at SCA 2012 in Switzerland. The work was done in collaboration with the Technical University of Denmark, the University of Copenhagen, the University of Utah and the University of British Columbia. You can find the abstract here. In the near future, we will add a preprint as well as a video.

[UPDATE] We won the Best Paper award! Yay!

Going to HPG and SIGGRAPH!

Brian Bunch Christensen — Mon, 01 Aug 2011 07:50:15 +0000

We are leaving for HPG and SIGGRAPH on Thursday. If you want to meet up with us, throw an e-mail at brian.bunch @ alexandra.dk

Real-Time Subsurface Scattering Teaser

Brian Bunch Christensen — Wed, 02 Mar 2011 15:52:52 +0000

A teaser showing off our newest research project result on real-time subsurface scattering.

“Particle Director” Unity Extension Released

Brian Bunch Christensen — Thu, 24 Feb 2011 10:03:18 +0000

Our first Unity extension – Particle Director – just went live on the Unity Asset Store today. It is a tool for specifying custom particle velocities for particle systems. With it you are able to specify motion of the particles by placing control vectors, solids, sources, sinks, etc.

Check it out here.

Unity Custom Particle System Demo

Brian Bunch Christensen — Fri, 11 Feb 2011 11:59:54 +0000

We have been working on a customizable, artist-friendly way of specifying particle velocities for particle systems in Unity. The built-in particle system animator only allows for a very limited range of motions, and it would be really hard to make the particles flow around obstacles or create vortices.

But before we dive into the details of our custom particle editor, why don’t you have a look at the result in the demo below? (We also demonstrate a Unity implementation of the shimmer shader effect from the previous post as well as a shader which creates foggy mirrors)

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The screenshot below shows our editor in action. You are able to specify motion of the particles in a 2D plane by placing control vectors, solids, sources, sinks, etc. Velocities are then computed for the entire plane by running a fluid solver for a certain amount of iterations using your inputs as boundary conditions. This only takes a few seconds and ensures that you get a nice and smooth velocity field in the entire plane. In the scene view, control vectors, solids, sources and sinks are displayed in order to help with aligning the motion with the scene geometry.

We have chosen to create a 2D editor instead of a full 3D editor since it greatly simplifies the user interface as well as reducing the computational load of the fluid solver. Our system still allows you to create 3D motions by extrapolating the 2D motion into space using a linear fall-off.
But more importantly, the system allows for using a linear combination of several velocity fields. Therefore, to specify a 3D motion you create several 2D motions and position them differently in your scene. The below screenshots show 5 planes combined to create a swirling, tornado-like motion. The highlighted plane in the left image specifies the horizontal motion, while the the highlighted plane in the right image and the 3 remaining planes contain sources and dictate an upwards motion.

The custom particle system fully integrates with the built-in particle emitter, animator and renderer meaning that all other aspects – save for the motion of the particles – are handled in the usual way. Other highlights include the ability to:

Emit particles from your custom sources rather than the single particle emitter
Add vortices to the velocity field
Change the weight of each velocity field separately at runtime, effectively turning on and off various motions

We plan on putting this custom particle system and editor on the Unity Asset Store in the near future.