1958 Aerial Mosaic, Steiner Ranch, Travis County

50dpi version of the original 300dpi 16″x20″ print

About this Map

The main image was assembled in 2018 from several individual aerial photographs taken over 60 years ago. The public domain images are available through a web repository owned by the City of Austin. I learned about them while researching the path of a Boy Scout trail that used to pass through Steiner Ranch. The whole poster idea came about after I had created the mosaic for my research. My wife said “You should print that and put it up at Cups & Cones.” I listen to her most of the time. 😉 You can view it there if you’re in the neighborhood. I had the idea for the “classic” border. I’m open to ideas for other formats/media. Contact me through the e-mail link at to left if you are interested.

The Lone Star Trail

Today Marks 69 Years Since The Opening Of The Lone Star Trail


I’ve been researching the trail (off and on) since 2003 when I stumbled across a mysterious metal marker in Austin’s Emma Long Park.

Trail? There wasn’t a trail there as far as I could tell. I had no idea how old the marker was. The marker was just nailed to a tree, way back in the woods. The ground around it was undisturbed, maybe for a decade according to my first underestimate. Yes, this plaque turned out to be older than I imagined.

As I found it 11/14/2003

Back then, I took a picture and moved on. I was hunting something else, a geocache that promised to be somewhere nearby. I set the mystery aside for a while. I posted a photo of the marker with a question about its unknown (to me) history to the internet in 2005. I got the break I needed in 2012 when someone finally associated it with the old Camp Tom Wooten.

Just a quick note: The trail is not to be confused the Lone Star Hiking Trail that winds through the Sam Houston National Forest. This trail is older, and was opened April 23rd, 1950.

Camp Tom Wooten was the big Boy Scout camp near Austin, operating from about 1937-1972. It was out where The Courtyard neighborhood is near the Pennybacker bridge. Eventually, I found Frank Hilton’s Lone Star Trail website, and the hand drawn map shown above. Wow, a real treasure map! Frank’s site is loaded with information. I greatly appreciate his efforts to keep and distribute the history. Since then, I’ve been looking into where the trail went. From the map, I found out that trail winds through the area where we live in Steiner Ranch, and through City Park / Emma Long Park where I found the marker. I’d already been to many of the places it passes through.

Recently, I’ve been using old City of Austin aerial photographs as overlays in the free Google Earth Pro desktop program to find the latitude and longitude of various places and trails I can see in those aerials. When I take the old overlays off, I can see the locations on a modern satellite image. Most of the trail is invisible from the air in 2019. I can see quite a bit in the 1966 aerials. There were less trees then. To date, I have not yet found any of these concrete milestone markers beyond the one for the start that has been moved to the museum (see below). I suspect they were all gathered up when the trail closed.

I’ve also contributed some to Frank’s web page. Namely the modern map (still incomplete) at the bottom of the page and the photo of the aluminum marker.

The trail started at Camp Tom Wooten (now closed and re-developed) and Frank’s website has some pictures of some spots along the trail. I have actually visited the cave shown in those pictures while geocaching.

During my research, I found that there was an exhibit for the trail at the Frank Fickett Scout Training and Service Center, and a bigger exhibit in the left half of the log cabin (below) at Lost Pines Scout Reservation near Bastrop.

Original Camp Tom Wooten administration/headquarters building
(now at Lost Pines Scout Reservation)
Camp Tom Wooten museum in the Log Cabin at at Lost Pines.
LST exhibit inside the Camp Tom Wooten museum at Lost Pines

In 2018, I retrieved the metal trail marker I’d located and turned it over to the museum. By then, it had fallen neatly from the tree and was ready to go.

I’m now using a much more powerful mapping program called ArcGIS Desktop, and am learning that to finish up a nice printable map.


Starr, Te (2012). Making a Difference Every Day – 100 Years of Central Texas Scouting – The History of the Capitol Area Council, Boy Scouts of America 1912-2012. Austin, Texas: Capitol Area Council

Mapping Tools

Google Earth Pro showing a 1940 Travis County Highway Map overlay and some waypoints

Continuing on the mapping theme, I wanted to talk about a few tools I use for my mapping activities.


I use an old Garmin eTrex Legend GPS receiver for my geocaching hobby and backwoods exploration. I purchased Garmin’s MapSource Topo in 2004, and I still use it today. The software isn’t updated much anymore, but it reliably moves waypoint and track data to and from my receiver. My map database is still original, but it isn’t a big issue as I don’t tend to use the unit for street navigation. I usually save “raw” field data in .gdb files, and also save a copy where I’ve cleaned up the tracks or edited waypoint symbology and labels. These files can be converted / imported into the programs below.

Google Earth Pro

I know most people know about Google Maps in their on-line or phone app form. Fewer people know about the free, downloadable PC/Mac app called Google Earth Pro. In addition to allowing you to view zoom-able maps of the entire globe, you can also make your own maps to share with others. The features I use are:

  • Satellite basemaps (recent historical imagery is available)
  • Track and waypoint overlays from my collected GPS data
  • Photo overlays of old maps and aerials (zoomed and rotated)
  • Getting coordinates of features in the overlays and basemaps.

You can also make cool map fly-over videos. It’s an awesome tool and a great place to start learning about making maps.

ArcGIS / ArcMap

Sometimes you need the real deal for mapping. In my case, I found that building a composite aerial map of around 16 photos in Google Earth Pro was bogging down the computer I was using. I also needed to stretch a hand drawn map in a non-uniform way to match the basemap. That task exceeded the capabilities of Google Earth Pro’s zoom and rotate (AKA affine transformation).

Esri’s ArcGIS / ArcMap does all of this work very well. It’s not so easy for casual users without mapping experience, but it’s definitely the way to go for people who are really into this stuff. It lets you stretch maps and aerial images to fit other maps (georeferencing) and uses variable image resolution to speed screen update time. This is the tool that makes most of the print maps you see today. I’ve completed a lot of on Esri’s on-line courses. It’s the next best thing to community college courses on the subject. I find learning this tool to be quite engaging, especially when paired with my interest in local history.


QGIS is another fantastic Geographical Information System program. It’s open source and free to use. It has many of the features of ArcGIS and its components. I did have great success in using the program to get beyond my issues in assembling the previously mentioned composite. On-line training is also readily available. I stopped using the program when I decided to start learning the more mainstream ArcGIS.

My Addiction to Maps

If you read my last blog post about Rutledge Spur, you might have noticed I’m into maps and aerial photos. I’m not just sort-of into them. Definitely addicted.

I’m not really sure when it started. I can vividly recall an early memory from when I was 7 years old. My family was moving from Ohio to Arizona and the moving company had supplied us kids with maps and an atlas. I remember following along from the back seat of our Fury III as we got to each town along the way, marking the progress along the highways we traveled. I was already pretty comfortable with maps at the time.

In grade school, a graduate student from the University of Arizona came to try to find out what skills our young minds used for navigating. He brought an aerial photo of the area around the school, and told me to walk us to a spot he was pointing at on the photo. I’d never had access to an aerial that showed our neighborhood before. My first question was “Where do you get these?” I knew it didn’t come from the gas station. I was thrilled to show him how to get there, using my skills counting streets, turns, and houses, but also using visual cues like trees and driveway styles. That guy did not expect a 4th or 5th grader to have that knack yet. He also told me he borrowed the photos from the U of A library. “Mom? Can we go there?” It turned out the graduate student’s borrowing privileges were higher than my elementary student privileges.

I enjoyed learning orienteering, compass, and mapping skills in the Boy Scouts. Gaining access to great topographical maps of the Santa Catalina Mountains fed my addiction, also prompting me to ask where they’d come from. That’s where I found out about Tucson Map and Flag. “Mom? Can we go there?” Alas, time, distance, and money kept me away.

In college, my eclipse chasing buddies were into maps too. At one point my housemate had plastered an entire wall with adjoining sections of the Baja peninsula. By then, I was able to provide transportation on a few trips to the map store.

My interest in aerial observation also stemmed from an interest in flying. I’m a window seat guy with a sore neck. I complteted ground school for becoming a private pilot and also did a few hours of flight time, but job changes kept me from continuing toward that goal at a couple of critical points. I still have lots of old aeronautical charts from those days.

As a defense contractor employee, I learned to use early military GPS receiver data streams at work. When they made accurate GPS available to regular citizens, Geocaching became possible. That was a real marriage of tech and the outdoors. That turned out to be a great match for me. Wow, how great is it that we have all this stuff on our smart phones now?

So, what’s the big draw maps for me? Probably the alternate way of looking at the world around me. Sometimes it’s getting the big picture: “How big is this park?” Sometimes it’s time travel: “What was here before?” Sometimes it’s getting there: “What way do I go?” And sometimes it’s a treasure hunt: “There’s something here I want to see.” The ultimate “treasure” for me is finding out something unexpected or unusual about a place.

The Rutledge Spur – Rediscovered

I’ve been looking maps and aerial photos of the area near the Marshall Ford / Mansfield Dam near Austin because the Lone Star Trail that I’m researching went through the area. In August 2018, I ran across aerial photos of the dam from 1940 on this City of Austin site. Note: You can click on the images of this post to see more detail.

Marshall Ford Dam under construction (1940)
(cropped from COA file 1940_COR-10-022_E.jp2)

In 1940, the dam was being built. It’s construction was the primary catalyst for change in our area; a huge change allowing Austin to grow and become what it is today.

As I used the Google Earth Pro desktop app to align the old aerial photo to the Google map of the modern roads, I came to realize that a second second “road” that paralleled the current RM 620 was not really a road.

Modern Google Earth imagery (top)
Composite 1940 aerial photos (bottom)
COA files 1940_COR-10-022_E, 032_W, 032_E

It was a railroad! The spur line was built by Brown and Root, Inc. of Austin, and McKenzie Construction Co. of San Antonio. They were also the construction contractors for the dam.[1] I think it was called the Rutledge Spur due to it’s origin at Rutledge Station in Rutledge, TX[2], but I’m not entirely sure. A Statesman article[6] indicates that this was part of the Houston and Central Texas Railway line. I had previously read about that very rail line in Carol MacIntosh Sikes‘ book Hudson Bend and the Birth of Lake Travis that I’d borrowed from the library in Lakeway. However, I did not realize that the rail line extended 11 miles east of the the dam construction area.

The rail line was temporary. It’s gone now. I’d lived in the Steiner Ranch area for 17 years, and never heard anything definitive of it until 2018 when I read Carol’s book. [Well, there were those few nights after we’d first moved here where I thought I heard an old steam train whistle from that direction, but I digress.] The dam was started in 1937[3], and that is when it was built. It was used to haul rock, steel, and equipment to the site. It’s been gone a long time. Northbound 620 now covers the old bed between Quinlan Park Road and RM 2222.

In the bottom half of the photo above (ca. 1940), you can see the dam under construction on the leftmost side. Note that in 1940, Lake Travis is not filled. In the center bottom (from later 1940), the lake is filled some more, but is not high enough to cover Horseshoe Bend (AKA Sometimes Islands). The railroad line (in orange) follows the Marshall Ford road (in blue) from the right, before deviating into a few turning sections and storage lines. The road does not go over the dam yet, but connects to the current low water crossing bridge. The white and yellow lines are the modern roads. An interesting old dirt road is in purple.

In the top half, you can see that the modern road is straighter, staying south of the current Marshall Ford Road.

Near the Dam Construction Site

Zooming in on the composite

To the right of the dam, in the center and north of Marshall Ford road (blue), you can see the cabins used by the building crews. They are arranged in a semicircle that goes out toward the lake. In the center of that, there is another row of cabins on a road extending north. I’d like to know if anyone can find names, maps, layouts, or other history for those camps.

Just past the hollow to the east on the south side of the Colorado River, you can see the clearing where the current Marshal Ford Foodmart sits. To the west of that was the Marshall Ford Bar. That bar burned down, I’m not sure when. Carol details a little about the bar in her book. I believe there were cabins behind these places as well.

Here’s an even closer look at the rail yard near the dam:

The rail yard near the dam construction side from COA file 1940_COR-10-022_E

The Low Water Crossing road is at the bottom of the picture. The comma shaped area above the rail line will eventually be the huge mound of rocks that are part of the east end of the dam. They probably pulled the tracks out as they started piling up the rocks, because those rocks are now on top of the old railroad beds in that spot.

Below is a panoramic view of the rail yard published in an early 1938 issue of Reclamation Era.[9] The photo’s written annotations identify some features visible from the aerial: The aggregate bins, mixing plant, and even where the earth embankment will go. To the south of the aggregate bins, at the end of the rail line is a two story structure that might be a rock or gravel sorter. It’s about the same shade as the background here, so it’s hard to see. In some other photos I’ve seen, it is often surrounded by a cloud of some sort. There were also rails on the other side of the river at the movable cableway head tower. Mansfield Dam Park is there now. I’m pretty sure the rail and building on the right side of the picture had already been removed by 1940, the date of the aerials.

The dam construction rail yard (1937-1938)

The grade to the Jollyville Plateau

1940 composite from COA files
1940_COR-16-032_E and RG114-DN0139-COR-9-026_W

The railroad (orange) deviated from Marshall Ford Road (blue) to ascend the hill near current Comanche Trail. It went south around the hill that the Steiner Steakhouse now occupies. Traces of the railroad ballast are still visible to the west of the steakhouse in Google Maps aerials. The 1940 aerial also reveals a dirt road “shortcut” to the current RM 2222 in purple. I wonder if that road had a name. It might have been “The Marble Falls Road” as mentioned in a 1932 story about an Native American burial site found in the area.[8]

The August 1937 issue of Reclamation Era[7] has the following photo that was probably taken from the SE part of the route around the hill. It’s stated to be about 3 miles from the dam site, and that’s what I measure along the rail line route. The cut through the rock still exists today, but is overgrown with trees. My family explored it found a railroad spike on the top of the “cliff” to the right in the photo.

Laying the rail for the railroad. Probable location of photo N30.38943° W97.87044°

Four Points (Hickmuntown), TX

Here’s a 1940 close-up at the location of the current RM 620 and RM 2222 intersection:

“Downtown” Hickmuntown
from COA file RG114-DN0139-COR-9-026_W

Hickmuntown? No, I’d never heard of it either. But, that’s what they used to call the Four Points area[5]. The railroad line is the straight line from top to bottom in the middle. Note that Bull Creek Road (FM 2222) is paved to the Marshall Ford road (RR 620) the paving only continues south from that point. What about the other dirt road just to the east and heading north from here? Well, technically, you are on it if you are entering/exiting current HEB by the gas station. That road went up to the current 620 and Boulder Lane (the south intersection of the two) before crossing over near 4 Paws at Four Points. It might have also been called the Marshall Ford road. Another possibility is the Anderson Mill Cutoff road. Where’s HEB? Well, it won’t be out here for almost 60 years.

Rutledge Spur between RM 2222 and Anderson Mill Road

Rutledge Spur in 1940 (left) and 2018 (right),
from RM 2222 in Four Points (bottom) to Anderson Mill Road (top)

The current RM 620 (in yellow on the right above) covers the old railroad path to the current US 183 (formerly SH 29). The section shown above is between RM 2222 in Four Points and Anderson Mill Road near Cedar Park. The red line on the right highlights that old dirt road that existed in 1940. It paralleled and crossed the railroad. It has to be the short-cut described in an article[4] from the Austin American.

Spur Tie-in to Southern Pacific at Rutledge

1940 aerial of the Rutledge Spur near current SH 183 and RM 620
from COA file 1940_COR-15-034_E

The spur’s tie-in to the Southern Pacific rail line was in Rutledge, Texas (now part of Austin). The tie-in is almost completely visible at the top right of the 1940 aerial above. That spot is near current Lakeline Mall Drive and Lyndhurst Street, and the current Lakeline Station. There is still a street called Rutledge Spur that terminates at the tie-in point. The crossed roads at the lower left are SH 29 and the road that will eventually be RM 620. I am unaware of the historical name of 620 at that time.


[1] Work Due Upon Rail Track to Marshall Ford, The Austin American (1914-1973), March 16, 1937: 1.

[2] Handbook of Texas Online, Frances W. Wynn, “RUTLEDGE, TX”, accessed April 12, 2019, http://www.tshaonline.org/handbook/online/articles/hvr81.

[3] Work Is Ordered On Dam, The Austin American (1914-1973), Jan 24, 1937: 1.

[4] Weeg, William J., Road Paved To Longest Lake In Playground Area, The Austin American (1914-1973), May 29, 1938: 18.

[5] Handbook of Texas Online, Vivian Elizabeth Smyrl, “FOUR POINTS, TX”, accessed April 12, 2019, http://www.tshaonline.org/handbook/online/articles/hvf90.

[6] Useless boulders turned into pretty Road Signs by Fruend, The Austin American (1914-1973), March 20, 1938: 8. Clipping on newspapers.com

[7] Photo 3 at bottom of page, Reclamation Era, Volume 27, No. 8, August, 1937: 183. Pdf available here. Note: The photos on this page seem disconnected from any articles in the issue. The caption tells the story.

[8] Indian Skeleton Found in Cave Near Here, The Austin Statesman (1914-1973), March 8, 1932: 10. Clipping on newspapers.com

[9] Photo B at top of page, Reclamation Era, Volume 28, No. 1, December, 1938: 12. Pdf available here.

Do you know more?

Your comments and corrections are welcome! Please feel free to share what you know here or contact me directly.

The Logo

Mulanax Electronics

I designed it in high school. I was working on some electronics projects and wanted to put a logo on them. This is what I came up with. The idea is basically an M for Mulanax with motor commutators around it. I was also thinking sturdy robot “hands”. The original color scheme was green and yellow.

The logo in 1983

I designed it so it could be stenciled in one or two steps. I also concentrated on using unit based layout and line thickness. At some point I reduced the outer radius by one unit, and narrowed the M. I remembered hearing that concentric circles and arrows emanated precision.

When I was working to upload it for the blog site today, I realized it looked a lot like a stove burner. Hey! Some custom colors to match the site palette, and here we are.

Where to go from here?

What direction is the wind blowing?

I’m looking for and preparing for my next career opportunity. My school and work experience are listed on LinkedIn.

I’m not one to just let the wind blow me to the next place. I want to put in some thought, so I can apply my efforts to move toward something that is going to continue to be relevant.

Where I am

My chosen career is computer engineering. To me, that’s designing computer systems that people and businesses need to get their tasks done. The design discipline has two main aspects: computer hardware (electronics) and computer software. I’ve gained lots of experience in both, and I definitely want to keep close to my experience base. Relevant experience will be what’s most useful to my employers in quickly getting their project completed.

Lots of my hardware designs have required software or firmware to complete the product, and most of them have required me to write some kind of functional test software before hand-off to other teams or the customer. Here is a subset of my skills that I see as being useful to employers going forward:

  • C/C++ programming
  • Python and Bash scripting
  • Verilog logic design
  • FPGAs
  • Hardware / embedded system design (board level schematics, circuits, PCB layout)

Which way is the wind blowing?

There’s been a shift in consumer hardware that has already affected my career. I took a while for it to sink in, but the shift to a smaller set of mass produced mobile platforms (phones and tablets) instead of individually engineered devices has translated to a smaller number of hardware products being developed. The smartphone is the hardware “hammer” that gets applied to most problems today. The phones take over as the general purpose computer and it’s chosen as the ready-made solution in lots of cases.

Where to next?

Being involved in the engineering of phones and phone chips has been good for me in the last few years. That might continue for a while longer, but the competitive field is narrowing. It does appear that there is increased interest in IoT hardware to connect to those phones. The devices are medical, industrial, and some home products.

So with the changes, I’ll probably have to shift focus a little. These are some adjacent engineering specializations that are in demand and appealing to me:

  • IoT communication
  • Machine learning
  • Cloud hardware and software
  • Blockchain and network security
  • Software defined radio

Finally, there are things that I’ve been interested in, but require a complete shift out of the computer engineering field, but hopefully not too much additional training:

  • 3D mechanical design
  • GIS mapping
  • Drone 3D surveys

I’ve been looking into inexpensive ways to train in all these fields and I’ve progressed well into a few of them. I’m not concentrating on any one thing too much as I’m not really sure where I’m going to get traction. My future posts to this blog will detail my progress. If you have any suggestions, or know anyone who is blogging about the same things, I’m open to hearing about it!

I took the image for this blog post at George Washington’s Mt. Vernon home in 2006.

The Star Display

What’s cookin?

I wanted a fun project to freshen up my Python programming skills and I happened on this idea while putting out my Christmas lights for 2018:

Let’s make a new yard display using individually addressable LED pixels!

If all goes well, I’ll be able to replace my existing display of mini light stars with a string of these cool computer controlled LED stars. I might even be able to synchronize the display to music!

Pixels and Pixel Strips

I chose the Worldsemi WS2812B as the pixel component for this design.

Each pixel includes three internal LEDs (a red, a green, and a blue), along with a built-in controller. The controller can set each of the three LEDs to one of 256 brightness levels.

The 2812s operate from a 5 volt supply, and each has a data-in and data-out pin for the serial control protocol. The components are daisy chained by their ins and outs with only 3 wires needed between each pixel. I think less wiring means less chance for wiring problems.

I picked BTF-LIGHTING‘s IP65 strips due to their low cost and waterproof design. I really like the simplicity of the flexible strip.

I’m not sure if the components they use are actual 2812s, but they are compatible with the protocol. I’m using the black, 30 pixels per meter variety in this project. The strips can be cut at the pads and have a thin, double sided tape backing.

Star Layout

The layout was carefully planned with a few constraints from the old display. I wanted to keep a similar star size, have pixels at the tips, and avoid overlapping pixels in the middle of the star. I used a quick Scratch program to verify my layout ideas using “turtle” or “pen” graphics. I decided on a strip of 45 pixels, and cut it into five 9-pixel sections. Each section forms part of a ten pixel chord that includes the start of the next strip.

Star Strips

The BTF strips need a support structure to hold them in the star shape. I decided to design my own plastic strip that could be 3D printed, then assembled into the star shape. The ends of the strips snap together and have slots to accept zip-ties that securely hold the pixel strips in place.

I found a mail-order supplier on TreatStock and had my parts printed in ABS plastic. I unexpectedly specified 20% infill on the order, but that worked out OK with the strips being somewhat flexible for the woven assembly I wanted.

Raspberry Pi

There are plenty of choices for LED pixel controllers. For me, the Raspberry Pi works great. I have a Raspberry Pi model 3 B, so I’m using it.

I’m running Raspbian (AKA Debian Stretch) Linux. The Pi is inexpensive, and out of the box, it offers a bunch of learning opportunities with free, open source software and development suites. Included HDMI, USB ports, WiFi, and Bluetooth make this a stand-alone computer that runs from a 5V wall-wart.


I’m using Maniacal Lab‘s awesome BiblioPixel light programming system to run the display. Their open source Python3 code library is hosted on GitHub. The package supports multiple pixel types, is portable to multiple operating systems, and comes with a lot of example animations. They support pixel layouts for one-dimensional strips, two-dimensional matrices and disks, as well as three-dimensional cubes. The animations are customizable via project files written in YAML or JSON. I was able to start with their animations very quickly using their built in strip layout. I had my own animation ideas for this star, and was able to program my own animation in Python. More on that later.


There’s one more component between the Raspberry Pi and the pixel strips. That’s Manaical Labs’ AllPixelMini.

It’s a USB device that handles the serial protocol that updates the pixel colors. This frees the Raspberry Pi of that CPU overhead and allows other real-time event driven software to co-exist on the system (audio, mouse, GUI, etc.)


In my setup, the AllPixelMini provides just the data signal (green wire) to the pixel strips (ignore the red wire above). A ground connection (white and black wires) is also required to make sure all the ground levels are common between the power supply, LEDs, and AllPixelMini. The All PixeMini gets it’s power (and ground) via the USB cable.

These 3-pin waterproof connectors work great for connecting the display to the power supply and AllPixelMini.

I plan on using the same connectors to daisy chain the stars and other display components when I scale this up.

Each 9-pixel strip is wired to the next with a 3-wire connection for 5 Volts, ground, and data.

The strips have solder pads on the back that let you keep the waterproof covering stuck to the LED side.

I also added adhesive lined heat-shrink tubing after soldering to keep the connections waterproof for outdoor use.

Power Supply

Each star of 45 pixels draws 1.66 Amps at 5V with all the LEDs of each pixel at full brightness, and 32mA in the quiescent “off” state. I’m using a 60 Amp, 5 volt supply driving the 5V rail of the LEDs directly (black and red wires connected to power supply above) without feeding power through the AllPixel Board. There’s plenty of power left for expansion, and the fan on the supply does not turn on with this light load.

Emitter Animation

When I first imagined the star display, I was thinking of the way firework streamers looked. You’ve probably seen animations that use particle systems to simulate fireworks. The firework explodes with glowing particles being emitted from a point. The particles stream down, flicker and fade before they burn out. This animation is similar.

The Emitter() animation is a one dimensional particle system for BiblioPixel. The animation is written in Python. My Emitter() class inherits from BiblioPixel’s Strip() animation class. You can find my GitHub repository here. Manaical Labs has also included it in their repository.

The Emitter() class has lots of parameters to control the particle effects, and the source code contains docstrings describing the parameters. Definitely check that out. The parameters can be overridden in BiblioPixel’s YAML or JSON project files. Here’s emitter_demo.yml for the demo in the video.

Each strip can have multiple emitters with programmable positions and velocities. Particles can be emitted in either or both directions. Moving emitters and particles can wrap at the end of the strip. The emitters can be invisible or have color.

Emitted particles move away from the source starting at the full brightness of a color that’s randomly selected from a palette. The brightness then varies in a random manner. The random variations are chosen from a list built at class initialization. The default settings should make the particles “sparkle” and fade. The distribution of brightness variations is adjustable.

Brightness Deltas

The Python code for plotting the histogram is here.

Individual particle velocities are random with adjustable constraints. Particles have a range and won’t go beyond a specified distance in pixels. from their emission point. At a given frame step, an emitter can start multiple particles. The starts_at_once parameter controls how many can start. The starts_prob parameter controls the probability that a particle will actually start. The variance in particle velocities lets particles overtake each other as they travel down the strip. Particles can hold a brightness level below zero and then randomly come back up above zero becoming visible again. Another effect is flares. The flare_prob parameter specifies the probability that a particle can immediately return to full brightness before resuming random brightness variations.

The particles are rendered onto the strip “screen” at each animation step. A loop goes through all the strip’s pixels and sees what particles or emitters are visible from that spot. If no particles are visible, the background color is used. The aperture parameter controls the “visibility” distance. If the distance to a particle is outside the aperture distance, it does not contribute to the pixel. The colors of the visible particles are then blended based on their distance to the given pixel. Particle positions, distances, and apertures are all floating point values. Small aperture values can cause blinking when a particle or emitter becomes invisible between the pixel locations. Larger aperture values will spread a particle’s color across multiple pixels.

See More

Check out this part of the star display demo to see all the parameters in action:

Old vs New

I spent a bit of time this morning trying to locate my copy of Forrest Mim’s Engineer’s Notebook. I was intending to write about that excellent publication being influential in my decision to become an engineer. I never did find its hiding spot. While I was hunting, I got to thinking about something else:

What do I really want to concentrate on for this new blog?

Do I want to detail my engineering history? i.e. just make a beefed up resume? Or, do I want to concentrate on the new stuff? I think I ought to lean toward the new stuff.

That said, the history of “me” really does pertain to what I’m working on now. The skills I’ve honed over time always lead me to believe I can approach a new task borrowing at least a little from what I already know. So it’s easy to say: “I can do that!” or, “I want to do it differently this time”. I’m sure I’ll get to talk about the old stuff as it comes up. That’s in my nature. I just don’t want to write only about history. I want make sure to write about now.

There is a nice write-up on the Mims notebooks over here.