A Procedural Model for Diverse Tree Species

Rama Hoetzlein
13th Procedural Content Generation (PCG) Workshop, Sept 5-8th, 2022

A Procedural Model for Diverse Tree Species, Pre-print
A Procedural Model for Diverse Tree Species, Talk Slides
Procedural Content Generation Workshop, 2022 Papers


The modeling of trees represents a unique and classical challenge in computer graphics. Models of 3D trees must express the form, complexity, structure, growth and diversity of real trees. Presently the most common methods for the modeling of 3D trees include a) user-based creative modeling, b) direct geometric capture such as LIDAR and photogrammetry, or c) indirect methods such as machine learning from images. These techniques often require significant human effort, large amounts of data, considerable computation resources, or any of the above. While there are methods that consider the direct procedural generation of trees, current models often require some human supervision to focus on naturally plausible variants. Instead, our approach is to construct a botanically inspired, harmonic, procedural model for trees which directly produces realistic yet diverse trees.

Knowledge Cultures in New Media Art

Rama Hoetzlein
ISEA 2022 International Symposium on Electronic Art, Barcelona, June 14th, 2022

Knowledge Cultures in New Media Art, Paper pre-print
Knowledge Cultures in New Media Art, ISEA Talk Slides
  Knowledge Cultures in New Media Art, ISEA 2022 Publication page

Knowledge Cultures examines the many creative sub-groups in New Media Art and seeks to identify their explicit, hidden or shared ideological principles. This paper defines knowledge cultures as flexible, overlapping, non-exclusive, ideological sub-groups and seeks to identify such groups within the practice and theory of New Media Art. While practicing groups may be associated with specific media such as games, 3D printing, or artificial intelligence, we seek to identify knowledge groups by their explicit, hidden or shared ideological principles.

Allegory of Forests

48″ x 96″, Oil on canvas

2019, FM Oakland Studios
2020, The In Art Gallery, Director’s Award (winner)

The Allegory of Forests is intentionally ambiguous. Is the narrative of the forest? or by the forest? Or perhaps it is a story told among many forests. Oil painting in large format allows me to explore spatial relationships not possible with photography. The forest fire, the secluded forest, the river, the glacier and the mountain coexist in a single space. These domains are not simultaneously visible in reality but are connected in actuality.

The forest fire references those of the immense Camp Fire that destroyed Paradise, California in 2018 (link). The fire was originally painted in reds and oranges when I discovered the partially unfinished white of the canvas lends an intense brightness similar to the real event. Titanium white is then used directly to complete the surface, giving the appearance of the canvas itself consuming the building structures.

People are absent, their impact is implied. Our objects remain to represent us. The absence of people is also indicative of tragic unease and disaster. During the fires, the entire SF Bay Area and California valley sheltered to avoid smoke while the residence of Paradise abandoned their town. Without the presence of people our buildings and vehicles appear unnatural and out of place.

Meanwhile, in remote places, horses and other animals live out their lives only remotely aware of human tragedy and its natural impacts. The effects, carried over great distances, are nevertheless persistent. Glaciers drip away in the distance (link). This ecology is lived and enacted within the space of the canvas.

Rama – Holiday Wish List

Hey Family & Friends,

I realize it can be difficult to find a gift for me. I don’t need much and have what I need. I created this page by request and suggestion. Rather than make you guess, this is a list of stuff that you might think that I normally have, but don’t because I always feel like I can just put it off. Small, useful things most people have that I find tedious to go buy. I really would appreciate these, I just don’t want to admit it 🙂

Every item here should be less than $40.


1″ Butcher Block cutting board.

Good cutting boards are hard to find. Less than 1″ will warp and buckle, and if not sealed properly they get moldy. A well-made, designer cutting board cost over $100 – don’t get! It’s just a nice piece of wood! I would make one for myself if I had the time. Minimal, wood, nice, thickness is key.


Knife Sharpener

Could really use one. But mostly don’t get one out of principle because I refuse to spend over $50 on a knife sharpener. Please don’t get me something on the right – these look fancy but will cost too much and break. A knife sharpener is simply a whetstone on a solid base (left). An antique shop might have one for $10.


Electric Hair Clipper

I’ve had mine for like 10+ years, but its reaching end-of-life. I haven’t been to a barber in same length of time – cut my own hair. Don’t need a close (screen) shaver. NOT cordless or battery, should plug in. Simple is better. $30 kits come with multiple depth attachments. Just always put it off because current one sort-of works, and I’ve fixed it like 3 times.


Serving Trays

I always thought it would be cool to have serving trays, so I could bring guests wine, or cheese, or whatever. I just never get around to it because I rarely have guests. But when people do visit, I wish I had these. Simplicity is key. Not fancy. Real bamboo, wood or metal. No fake materials.


Decent, 7-port, Powered USB 3.0 Hub

A simple, decent, powered USB hub that has 7 ports, with 900 milliamps per port for USB 3.0. Nothing fancy. Needs to provide enough power to supply three external hard drives. Not flakey.



Ok. 🙂
Just a warning, I have very specific tastes in clothing, so you’re getting in deep now.
This will be a short introduction to men’s shirts. Proceed at your own risk!

If you’ve made it this far, you must be serious.. Getting cloths as a gift for a man – that won’t be exchanged – is very hard.
– I am always in need of nice shirts.
– Not pants, not sweaters, not socks, not coats. Shirts.
– NO flowery shirts, NO plaid, NO paisly, NO stripes, NO checkers.
– NO bright colors, NO crazy designs, NO biker tats, NO logos, NO words really.
– This isn’t to say other guys won’t appreciate them, they’re just not my style.
– NO long sleeve! I live in Florida.
– The hard part is that too many shirts ‘try too hard’ to be cool. Here are examples of shirts NOT to get me:

– What I like are plain, solid and pastel colors, possibly with nice edging.
– It’s very difficult to find nice shirts.
– The proper name them is: mens casual short sleeve collar shirt, slim fit, size medium.
– Here are some good ones.

Those are two of my favorite shirts. Only $20 each.

– My best shirts are Danish, Swedish and Nordic, but designer shirts are too costly. This one was $120 overseas. But please don’t try this – buying European is a very personal process, I prefer to do myself. Notice it has a micro-pattern, with custom trim, and a local Dutch label, which you can’t find online. I only have one like this:

– Micro-patterns are interesting if they look solid from a distance.

This photos is from a Johnston & Murphy catalog. You can see a nice shirt design is very thought out.

– Here is the current set of shirts in my closet. Unfortunately, there aren’t enough colors, because colors are too often excessively bright and loud. I wish I had more subtle colors or micro-pattern. I like edging and colored threading (where the seams are done in a visible colored thread)

– Where to get shirts? Good shirts can be found at.. H&M, TJ Max, Kohls, Dressman, Guess, all for less than $20. Slightly higher up is Johnston & Murphy. I won’t go more designer fashion than that unless I travel.

Now you know something personal about me.

– As a professor… a good shirt says to your students: “I’m not trying to please you, I’m not joking, not kidding around, I’m not your parents, I’m not too cool, I’m not ancient, I’m not cheapo, I’m not poor or rich.. I’m just your teacher.. But I know how to dress.”

You know, you could just get me a cutting board.. 🙂

I feel that a genuine gift is something where you learn something about that person to really understand them more deeply. But if I haven’t seen you in years – and I am a private person – it could be very difficult to find out about me. Before I would never write this page. But my thinking now is that I want to try and reduce your unexpected gifts that might contribute to landfill. So here is a list of things that I don’t want..
– Please don’t get me trinkets or desk items. These will end up in my “hide forever” drawer, only to come out to prove to you I still have them.
– Don’t get me humorous or joke items. Unless it is an inside joke that just you and I can appreciate.
– Don’t get me large items. I prefer minimalism and open, uncluttered spaces.
– Don’t get me delicate things. On the airplane or in shipping they will break. Will also end up in hide drawer.
– If you really want to get me a creative, sentimental gift, then you really need to know me well enough to know what themes I like. Since I don’t share often I can see how this would be hard.

Simple, functional, household items is your best bet, because they will serve a purpose without adding to waste or to the hidden items box. But not random. I don’t need a tomato slicer because a knife if just fine. See list above.

Anything functional above would be just perfect. Less than $40.

I enjoy a simple life. I like things to work nicely, yet often postpone fixes out of principle or refuse to give into costly, cheaply made products.

If you’re on this page, now you know 🙂



Race to Virtual Reality:
The Future of VR Headset Visual Acuity

The release of the Oculus Rift DK1 in 2013 brought Virtual Reality to the mainstream, again. With low latency and 110 degree field-of-view, for the first time this offered a reasonably priced VR headset that doesn’t make people nauseous (for most). Since then companies such as HTC, Samsung and Oculus have entered and propelled the VR Headset market forward. None-the-less building a good VR Headset is a difficult challenge as consumers expect high resolution, wide field-of-view, low latency, and decent contrast.

To understand trends in VR Headsets we look at visual acuity as measured in pixels per degree (ppd). While other measures are also important, such as field-of-view, this metric indicates the visual density of the device – a strong factor in the perception of quality and reduction of the pixel grid effect. Although this market is still in very early development, analysis of VR Headsets from 2013 to 2019 shows a roughly linear growth in ppd (left side of image). The Oculus Rift DK1 from 2013 has an acuity of 5.8 ppd, whereas the more recent Gear VR from 2019 has an acuity of 16 ppd.

Meanwhile, looking at recorded 360-degree Video Content (right side of image), we see a trend from 2K to 4K in the past 5 years, with the future looking at 8K content. There is currently very little 8K video content but that is expected to change. More importantly the technology for 8K video recording and playback is now possible. With a 360 degree field-of-view 8K video content contains an acuity of 22 ppd, surpassing the most modern headsets. In other words, even with the best VR headset you won’t be able to make out all the details found in an 360-degree 8K video.

Human vision has an acuity of 60 ppd – up to 12,000 pixels across a 210 degree field-of-view. A linear trend shows that VR Headsets will slowly inch their way toward this goal, depending primarily on the OLED and related markets to push higher screen pixel densities. At the current rate, we can estimate that VR Headsets may match human visual acuity by the year 2070. Thus you might not want to wait for the “perfect” headset as it could be a while. In the meantime factors such as field-of-view, low latency, contrast, tracking and interaction will provide a great deal of variety in the market before we get there. By 2100, a century from now, people could be enjoying VR experiences as richly detailed as waking life – hopefully with sunglasses instead of heavy headsets.

The following are a set of resources to help understand modern global change.

There is strong need for thoughtful discussion to return to American thinking. Whereas the news media focuses on sensational or irrelevant points they often miss the fundamentals for the sake of superficial debate. This list of essential resources is intended for the general public and presents important authors in major fields of study that everyone should know. The lectures and films are intended for more visual thinkers, while the writings and books are for intellectual readers or for those who wish to go deeper.

Resources were chosen based on their relevance to global issues, the importance of its contribution to other fields, the importance of concepts to raise public awareness, and clarity of presentation or writing to a public audience.

Field Author Media Resource
Climate Greta Thunberg Interview School Strike for Climate: 15-Year-Old Activist
Speech Writing Save the World by Changing the Rules
Womens Rights Tarana Burke Lecture Me Too is a movement, not a moment
Rituparna Bhattacharya Paper #MeToo Movement: An Awareness Campaign
Policy Alexandra Ocassio-Cortez Interview Rep. AOC Explains Why the Green New Deal is About More than Climate
House Resolution The Green New Deal
Labor Elizabeth Warren Lecture The Coming Collapse of the Middle Class
Paper The Growing Threat to Middle Class Families
City Planning Elon Musk Interview The Future we’re building – and boring (tunneling)
Computer Science Lee Sudol vs. AlphaGo Documentary Film AlphaGo (Artificial Intelligence)
Biology Marla Spivak Lecture Why bees are dissapearing
Paper The Plight of the Bees
Energy Michael Shellenberger Lecture Why renewables can’t save the planet
Book Break Through: From the Death of Environmentalism to the Politics of Possibility
Relationships Esther Perel Lecture Rethinking infidelity.. a talk for anyone who has ever loved
Miller McPherson Paper Social Isolation in America: Changes in Core Discussion Networks in over Two Decades
Education Davis Guggenheim Documentary Film Waiting for Superman
Hannh Ardent Paper The Crisis in Education

Comments or additional suggestions are welcome below.

by Rama Karl Hoetzlein and Andy Hacket

Full document

We are pleased to offer the full document here (CC-BY):

 A Practical Guide to Rudderless Sailing

Why sail rudderless?

We believe that rudderless sailing allows the novice sailor to improve boat balance, sail trim and centerboard control much more directly. The rudder provides a guarantee for your point of sail whereas rudderless involves maintaining your point of sail by understanding and feeling all the forces on the boat. Aside from its help in managing rudder failures, we believe that rudderless gives the sailor a better intuitive sense for how to trim and balance a boat; which is valuable for performance sailing, sail trim and general good form.

A few motivations for this guide. First, we’d like to mention Joel Brand’s e-book Rudderless Sailing from 2013 as an excellent review of rudderless sailing theory. We are also inspired by Harry Morton and Israel Smith’s youtube video “29er No rudder sailing with Dave O’Connor” from 2012 which demonstrates two-handed rudderless on a small 29’er – with a spinnaker! Pretty amazing sailing, and still one of the few videos of rudderless with tacks and jibes. This isn’t to say there aren’t many great rudderless sailors. Yet we feel the lack of examples is because it is currently viewed as an extra skill rather than as a form. We hope to change that.

The primary reason for this Practical Guide to Rudderless is to provide a starting point for any club or novice sailor to learn rudderless as a way to intuitively feel the forces on the boat. While we briefly touch on theory, our focus is on a practical guide that helps you to understand what is happening when you’re on the water. Of course nothing can replace actual sailing. So our intention is to give you an idea of what you’re likely to experience, the tools you have to respond to it, and exercises to help you gradually improve.

This was a senior project with the Cal Sailing Club in Berkeley! Thanks for their support!

Questions & comments
Both are welcome below! We’re happy to provide this and hope to improve it.


VOX3 is a stereolithographic 3D printer with a voxel-based workflow. Stereolithography, or SLA, 3D printing uses a photosensitive liquid polymer to create hardened layers of material. Whereas laser SLA exposes each layer by tracing the outline of the part with a laser, projector-based SLA exposes a single layer all at once. This process is most similar to the Formlabs desktop 3D printing process.


The unique aspect of the VOX3 is a voxel workflow based on the NVIDIA Jetson TX2. A typical workflow for 3D printing is to model a part with polygons, then load the part on a CPU host which performs voxelization and then generates either G-code or the slice images required for SLA printing.

By running GVDB Voxels on the Jetson TX2, we are able to perform advanced processing in the printer itself. The Jetson TX2 has dual video outputs, enabling it to run the slice projector and a preview monitor. Using 256 parallel CUDA cores, the Jetson TX2 can process polygonal and voxel models on the device. This workflow implies the ability to transmit, process, in-fill and slice volumetric data directly on the 3D printer.

The VOX3 workflow allows for live processing of the part during printing. Although not used in our prototype, feedback from the printer via cameras and sensors could be sent to the Jetson to make live adjustments. Additionally, re-processing can be performed since the VOX3 has full access to the original and voxelized model in printer memory. In our demo the VOX3 takes a polygonal model as input, performs full, high resolution voxelization to a sparse 3D volume, and computes each cross sections on-the-fly as needed for projection while printing.


Figure 1. Frame assembly

The VOX3 was designed as an experimental prototype. The process of bottom-up SLA printing requires a projector, a built tray, a moving build platform and a mold release mechanism. Figure 1 shows the basic frame assembly. The Z-axis and build platform are controlled with a leadscrew and a 1A stepper motor. The front mounted motor is used to tilt the build tray after each printed layer.

Figure 2. First projection test

With the frame designed as two stacked aluminum cubes, the projector is mounted in the lower cube and points upward at the build tray. Figure 2 shows the first projection test.

Figure 3. Completed VOX3 printer

The completed 3D printer is shown in Figure 3 with the Jetson TX2 (panel top left), and a Smoothieboard (panel bottom left) which controls the two stepper motors. Special UV transparent glass (center) is required so that the projector light has sufficient power density to polymerize the SLA liquid. The build tray holds the liquid, not shown in this photograph.


The VOX3 was exhibit at the 2017 GPU Technology Conference as part of the NVIDIA display on Optimized 3D Printing with the GVDB Voxels software. Since resin printing can be messy and requires refilling, the display was operated in demo mode which shows the moving printer head and 3D slices computed in real-time.

Also exhibit were 3D printed parts made by Voronoi in-filling with GVDB Voxels. The Lucy model was printed as both a solid part and with voronoi filling to demonstrate weight reduction computed interactively and entirely with voxels.



Rama Hoezlein, Ph.D Disseratation, 2010
Media Arts & Technology Program, University of California Santa Barbara
Committee: Tobias Hollerer (Computer Science), George Legrady (Media Arts), Laurie Monahan (Art History)

LUNA is a visual language for dynamic procedural modeling. Created with a custom graph-based language, LUNA adopts a tile metaphor to enable rapid experimentation with dynamic geometric operators. The data flowing through the LUNA graph consists of multimedia objects such as images, meshes, geometric instances, sounds and text. Luna was developed as a dissertation on the benefits and limitations of creativity support tools in computer graphics and media arts.



Ch 2. Tools for the Visual Media Artist: A Survey

Ch 3. LUNA: A Puzzle-Based Metaphor for Procedural Modeling

Ch 4. Procedural Modeling of Complex Objects using the GPU

Ch 5. Emergent Behavior: A Functional Analysis of Art

Ch 6. Digital Bricolage

Ch 7. Structure in Dynamic Media



Figure 1. This video shows real-time procedural control of a flocking simulation from a Microsoft Kinect device. The arm angles of the user determine the attraction force pulling the flock into a spiral. (Click video to play)


Figure 2. This video shows dynamic displacement mapping with input from a 2D wave simulation, in addition to other real-time mesh deformation effects. (Click video to play)


MAKH (c) Rama Hoetzlein, 2004


Rama Hoetzlein (c) 2004 & 2014
Machines, motors, tape players, and cinematography

MAKH is a convergence of ‘Making’ and ‘Machinima’. Making follows the makerspace movement and ethos; creation through DIY design, mechanics, and electronics. Machinima is the development of film making and narrative through the use of record video game play. MAK’H is a combination of these trends – a convergence of ad-hoc mechanics and cinematography. A central theme in makh is the democratization of film making, and the notion that anything animate, whether it be video games, animals, or machines, can lead to visual narrative. Makh re-imagines making as a process in which the completed object irrelevant (there is no finished), and re-imagines cinematography as narrative derived from anything animate.