# Tag Archives: Screencast

## Three things I learned at ScreencastCamp

Last week, I had the chance to attend ScreencastCamp, a weekend event put on by Techsmith, Inc. just down M-6 in Okemos, Michigan. What a great experience! Techsmith develops Camtasia, my go-to software for all screencasting needs, as well as several other great products like Jing and SnagIt. I’ve been a fan of their products for a long time, and it was great to spend time getting to know the people behind them.

ScreencastCamp was an unconference, where there is no set agenda beforehand. Participants just come with an idea of what they want to learn, and then either put on a session or request one. There were about 40 of us participating, mostly from education but with a healthy contingent from the corporate (training) world as well. Amazingly, although this is a relatively small number of participants, all the session slots for Saturday and Sunday filled up almost immediately as people pencilled themselves in to give sessions. It was busy. Some of the sessions were like regular conference talks, while others ended up as discussions among four or five like-minded people sitting around on the sofas in a back area of Techsmith headquarters. The hosts were generous, the food (and the beer!) amazing, and the atmosphere of enthusiasm infectious.

I came away with a lot of great ideas about screencasting, but here are the three that stood out the most.

1. Write careful and complete scripts for your screencasts. Back in my series of “How I Do Screencasting” posts, I wrote that a rough script was the way to go. Now I’m a believer in complete, careful, tightly-written and -edited scripts. What’s so great about a complete script? First of all, I have a tendency to talk fast and speed up as I get going in a screencast. Scripting out what I’m going to say not only helps me to edit my thoughts down to just the essential ideas, it also provides a way to talk at a normal, relaxed pace. Second, having a script printed out in front of me will make it easier to caption my videos, which is something that I want to start doing and indeed may eventually have to do. If I have a script, I can copy and paste the text of my screencast into Camtasia for the captions. It’s a little more complicated than that sounds, but at least I wouldn’t have to transcribe the audio.

Techsmith gave us a copy of the template (MS Word, 66 Kb with a bunch of my own stuff on it) they use for their own screencast scripts. I’ve used this simple form for a series of Maple 15 screencasts I’m working on right now, and it’s really made things go a lot more smoothly than when I was reading from a text file, or making it up as I go.

2. Record your audio first, then your video. This was the most radical idea I heard. I had always recorded the audio and the video simultaneously using Camtasia, but that’s not how Techsmith themselves do it. After writing the script, Techsmith screencasters will read the script and record the audio using Audacity. Then the audio file gets exported into Camtasia as an audio track, and the video part is recorded on top of the audio separately. At first I was very skeptical of this (wouldn’t it be a lot more work?) but after trying it myself, I’m a convert. Recording the audio separately reduces cognitive load — you don’t have to worry about getting both the audio and the video right at the same time — and so both pieces turn out better. Audio is much easier to edit when it’s not attached at the hip to video, I think. And you can focus on the quality of the audio as well. As one Techsmith employee put it, viewers will put up with crappy video as long as the audio is good, but not vice versa.

The way I’ve made this work for me is with the following workflow. First, write a good script using the Techsmith template. Then, read the script into Audacity, putting plenty of “white space” in between each box in the template — this gives viewers a little breathing room while they are watching. Next, go back and edit out any mistakes in the audio, either in Audacity or in Camtasia after the audio has been exported. Then, to record the video, turn off all audio inputs (because you’ve already done the audio), start recording the screen, then start the playback of the audio track and just click along with whatever it is you’re saying from the script. After all, this is what your viewers are going to have to do. Once you’re finished, it’s relatively simple to sync up the audio and video (especially if you keep the whole thing short) by just moving the tracks up and down the Camtasia timeline until it looks like they work. Then trim off the beginning and end of the video to make the video and audio the same length.

3. Get a real microphone. I’ve mentioned before that I’m too cheap to buy a USB microphone when the built-in mic on my Macbook works passably well. But after trying some of the higher-end equipment at Techsmith and hearing what it sounds like on playback, I think I might have to be, well, less cheap. When I recorded my practice screencast in the Techsmith studio, the mic captured the full range of my voice without sounding like I was at the bottom of a well, and no other sound made it into the audio. Part of that is because I was in a studio, as opposed to my office, but part of it is the microphone. It really does make a difference.

I also picked up a ton of little tricks and tips from participants — for example, buy a dog clicker to use when you make a mistake on the audio; the spike it makes in the audio waveform is really clear and it makes it easy to find where you need to edit.

ScreencastCamp was a great experience — amazingly, it was totally free too — and I learned a great deal about how to be a better screencaster. Thanks Techsmith!

## How I make screencasts: The whiteboard screencast

In this post, the fifth in a series of posts on how I make screencasts, I’m going to focus on what I call the “whiteboard” screencast. This is a screencast where I am demoing some sort of concept or calculation by writing things down, rather than clicking through a Keynote presentation or typing something on the screen. It’s intended to mimic the live presentation of content on a whiteboard, hence my name for it.

Of course the most well-known examples of “whiteboard” screencasts are the videos at Khan Academy. In the unlikely event you haven’t seen a Khan Academy video before, here’s one:

I do whiteboard screencasts fairly often. I use them sometimes for presenting hand calculations for students to watch and work through before class, and sometimes (probably more frequently) I use them to create additional examples for things I’ve covered in class. This is a really powerful use of screencasts — students often want more examples than there is time for in a class meeting, and whiteboard screencasts give me a way to give students as many examples as they can dream up.

The basic principles of whiteboard screencasts are the same as for other screencasts. You first have to engage in basic planning, which involves defining a tight and coherent scope for your screencast and writing out a script. For whiteboard screencasting, which is more free-form than lecture capture using Keynote or PowerPoint, the scripting process has to be a little more rigorous. Because it’s easy for me to get carried away when talking about something that matters to me, I find it very helpful to work out in advance everything that I am going to do in the screencast, in the order and position on the screen that I intend to do it. I don’t always read words from a script, but in order to make the screencast logical and coherent, I do storyboard what I am going to do and practice with the drawings, erasures, and such. Very little of what I do in a whiteboard screencast is ad-libbed. (If I were better at ad-libbing, that might be different.)

So I will start a whiteboard screencast with something like a mind-map of the topic or topics I intend to address and one, maybe two, examples of that topic. Additional topics go into additional screencasts. I work those examples all the way through to ensure that there are no math or other mistakes and that I don’t get stuck in one of my own calculations. If you think about it, this is just the same kind of planning that goes into a successful whiteboard lecture, so this process is not entirely alien to instructors.

Once the screencast is properly planned, it’s time to put it together. This is where it gets technically somewhat complicated. But a lot of people ask me about the tools I use to make whiteboard screencasts, so hopefully this will be worth it. I use four main tools for doing whiteboard screencasts:

• Keynote; I’ll explain in a minute.
• Camtasia, which we saw in the last post in this series.
• FlySketch, a software app from Flying Meat (they also make the popular personal wiki software VoodooPad). FlySketch puts a transparent overlay on top of any existing objects on your computer screen and allows you to draw freehand, draw geometric shapes, or type text on the overlay. See the link for screenshots and a more detailed description.
• A Wacom pen tablet. I currently a Wacom Graphire tablet purchased with a grant a few years ago. With my upcoming job change, I have to hand that in when I leave, so I plan on picking up a Bamboo Pen & Touch this fall.

With those tools, here is the workflow I follow for making a whiteboard screencast.

First, open up Keynote and make a single, blank white slide. This is going to be the “whiteboard” itself. Of course you could also use a blank MS Word document, or any other blank white window or screen. Keynote is just for convenience’s sake.

Next, open up FlySketch and lay it completely over the blank window so that the controls are showing above the top of the window:

Then, open Camtasia and create a custom region that encompasses the “whiteboard”. When the video rolls, it will record what is happening on the whiteboard:

And finally — start the video, and start writing on the FlySketch overlay using the Wacom tablet. Before you start recording, make sure to select the pen color and size you want. If you need to change color, size, or pen type during the screencast — say, you want to switch from freehand writing to typing, or drawing a straight line for an axis — you can tap on the appropriate FlySketch control and Camtasia won’t record it because it’s off-screen.

Then you simply record what you need, then stop, and process the video as was described in the previous post in this series. This includes editing out any mistakes and splicing together multiple video clips for the same screencast.

Here’s an example of the finished product:

Although Sal Khan has been my inspiration for doing screencasts, I’ve made some conscious decisions here to do things differently than Khan does. First, I prefer the white background to the black; it’s more familiar to learners and seems cleaner. I also tend to use thicker pen “tips” than Khan does; I tend to think his pens look a little spidery. Also, the Wacom tablet pen is pressure-sensitive, and that feature works better if the pen tip is thicker. Finally, from a planning perspective, my whiteboard screencasts are a lot less conversational than Khan’s videos. Khan tends to shoot from the hip in terms of presentation; this is part of what makes his videos so charming, but I think it also tends to make his videos go longer than they need to. I prefer to make things a bit more efficient and focused and take less time. It also cuts down on mistakes.

I think the hardest part of this process, for me, was mastering the art of writing on the Wacom tablet in one place and having the writing appear on the screen. This is harder than it sounds! At first my handwriting was horrible (I think at the time I likened it to somebody with a brain injury) but eventually I got my act together. I suspect people learning to play the drums or the piano have to go through the same process before it sounds any good.

Another challenge is managing the relatively small amount of physical space you are working with. A Keynote slide is just not a very large place, and it’s easy to run out of room when writing. If this happens, it can be dealt with by just starting another slide and creating a new video clip. But it’s better for the learner to see one example per slide if possible, and making sure this happens is part of that all-important planning process. I find it helpful to practice the presentation not on the screen or a piece of paper but on a 3 x 5 inch notecard, which has something much closer the same proportions for writing as the Keynote slide on the screen. But note that it does take practice — if you just sit down and try to bang out a whiteboard screencast, it’s likely not to be as good or as instructional as possible, and it could end up taking more time in terms of edits and re-takes than it would if you just planned and practiced in the first place.

I’d be interested in hearing any alternative approaches for making these kinds of screencasts. I once wrote Sal Khan and asked him what his tools were, but never got a response, so I just reverse-engineered what he was doing. There may be a better way. Let me know!

Next up will be the final installment in this series, touching on what I called a “demo” screencast. It’s probably what I do the most. Stay tuned!

## How I make screencasts: Lecture capture, part 2

Now that school’s out, I’m going to pick up where I left off (two months ago!) in my series on how I make screencasts. So far I’ve made three posts in this series. In the first post we talked about what a screencast is, exactly, and why anybody would want to make one. In the second post, we saw how the elements of careful planning make screencasting a successful experience. And in the most recent post, we took a look at using Keynote (or PowerPoint) to create a lecture-capture screencast.

Before I talk about the other kinds of screencasts I make, I’m going to take this post to describe how I use my go-to tool for screencasting: Camtasia for Mac, specifically how I use it to make lecture capture videos when I’m not using Keynote. (Full disclosure: I was on the beta-testing team for Camtasia for Mac and got a free license for the software for my efforts. But I can definitely say that I’d gladly have paid the $99 for the software otherwise — it’s that useful.) There is a Windows version of Camtasia and a server-oriented variant called Camtasia Relay, and they are all very similar, so what I describe in this post can be used if lots of different situations. Let’s suppose I have a lecture or presentation that I want to turn into a screencast, which basically means I need to record the presentation as it happens on the screen and add a voice-over. I’ve already described how to do this with Keynote or PowerPoint, but what if you’re using Prezi, Beamer, or some other presentation tool? What I need is a tool that will record stuff happening on the screen that’s separate from the presentation tool itself. That’s where Camtasia comes in. Camtasia is software that records video of anything happening on your screen — all of it, or part of it — along with any audio you choose to add, including voiceovers. You can record multiple segments of video, edit those segments, and put it all together with transitions and effects. The interface is laid out a lot like iMovie, so Mac users will feel right at home using it. There are a lot — seriously, a lot — of options for working with video in Camtasia, too many to get into here. I’ll just show an example of a simple lecture capture putting Prezi and Camtasia together. First, bring up the screen that has the Prezi in it. (For Prezis particularly, creating the lecture capture works best if you download the Prezi to your local drive and then run it in a window, rather than trying to run it on the web.) Now launch Camtasia. When you do, a little floating pane will come up that looks like this: The dropdown menu on the left lets you specify which part of the screen you’re going to capture. I usually just select “YouTube HD/720p”, which records essentially the entire screen. I can crop out what I don’t need later. And once I put it on YouTube (which is my usual destination for screencasts) it’ll be in glorious 720p HD. Once you’ve selected your area, just click the Record button and start presenting, just as you would if you were giving the lecture in front of a live audience. Your lecture is being recorded behind the scenes and all you see is your screen. Warning: Presenting for a screencast feels a lot different than doing it for a live audience because, well, the audience isn’t there. There’s no body language or ambience to add to the presentation. So this will feel a little unusual at first. Also, I can’t stress enough that you should probably go from a prepared script the first few times you do this, rather than try to wing it. It’ll keep you on track and prevent lots of mistakes. When you stop recording, you’re brought into the main editing area of Camtasia: The bottom part of this screen is called the “timeline”. Right now, the one clip that I have in the timeline is a partial video of the presentation. It appears as a chunk of the timeline outlined in blue. Inside the timeline you can see the audio levels given as waveforms, and there’s a playhead along the top of the timeline showing you where you are in the video as well as the time. At this point, what I usually do is check the sound levels first. A lot of times the built-in microphone on my Macbook doesn’t record very loudly. I’ll listen to a bit of the recorded video to check if that is the case. If so, I go and apply the Dynamics Processor effect to the clip I made: You apply the clip just by dragging it from the effects area directly onto the clip in the timeline. In fact this is how all the effects, transitions, and other features of Camtasia are applied to video. The Dynamics Processor brings all audio levels up to a uniformly audible setting. If I have the time, I will watch the whole video from start to finish to see if I’m happy with it. If there’s something I need to edit out — I goofed the script, or sneezed, or the phone rang, etc. — I can go back and edit that part out just by putting the playhead just before the mistake: Then selecting “Split selected at playhead” from the Edit menu; this splits the video clip in two, right where the blooper is. Then move the playhead until just after the mistake, and selecting “Trim Start to Playhead”. This will crop out the blooper from the second clip. Then you can just drag the second clip over next to the first one, and with that, the blooper is edited out. The ability to edit in such an easy way really changed screencasting for me. You will make mistakes when you screencast, no matter how good or experienced you get. But you don’t want to have to throw away an entire screencast because of one goof. If I am screencasting and I make a mistake, I just pause for a moment, and then I start again from the point of error. The pause will show up on the audio as a flat spot, and I can go back and edit the error out. You cannot do this with the voiceover features of Keynote and PowerPoint, and it makes a huge difference. If this is just a straight lecture capture — so there’s no other video coming in from a different source — at this point I’m done. The only thing left to do is add the “credits page” that I always put at the end of my screencasts that lists my email, YouTube channel, Twitter, and so on. I have this saved as a PDF. To bring it into the timeline, I go to Import Media: and select it from the file finder. It then appears as a clip: I just drag it into the timeline at the end of the video: And then, for effect, add a fade-in transition from the video to the credits, which I do by finding it in the transitions menu: And dragging and dropping it in the little seam between the video clip and the credits page: Now I’m ready to publish. Camtasia allows me to publish the resulting video directly to my YouTube channel using the Share menu: As you can see, there are options for iTunes and Screencast.com as well. Or you can just choose “Export…” which exports the video to a file format of your choice, for uploading wherever you want. After I start the process, Camtasia converts the video to Quicktime and then uploads it with the title I gave it. A 10-minute video will take several minutes to complete this process on a Macbook Pro. Your mileage will vary according to your system hardware and your internet connection. After it’s done uploading, I still have to go to YouTube and add metadata. But otherwise that’s it! What’s nice about Camtasia is that the tool is separate from the presentation tool you’re using. So if you already have the presentation content made up, you can turn it into a screencast quite easily. It doesn’t matter whether it’s Prezi, Beamer, a text document you’re scrolling down, or anything else. And the more you do this, the easier it gets to convert existing presentation content into a mobile device-friendly screencast. In the next post, I’ll talk about what I call “whiteboard” screencasts, where I record stuff that I am writing on the screen. This is a lot like what Salman Khan at Khan Academy does. Hopefully it won’t be another two months before I get to that. ## How I make screencasts: Lecture capture, part 1 Image via Wikipedia Sorry for the time in between posts lately. It’s been an odd mix of attending conferences, getting ready to attend conferences, and spending time in the hospital being treated for skin infections picked up at those conferences for the last couple of weeks. Long story. Let’s talk about something more pleasant than cellulitis, namely screencasting. So far I’ve posted about the general idea of screencasting and what I do with screencasts, and I’ve posted about the all-important planning phase of screencasating. Now I’m ready to start getting to the nuts and bolts. Of the three kinds of screencasts I do, probably the simplest is the lecture capture. In a lecture capture I am simply recording a slide presentation or a Prezi with a voiceover. Here’s an example, which is an overview of the first test being given to a freshman calculus class: All this screencast is, is a Keynote slide deck that I prepared with a voiceover. Sometimes this is all you need for the task you want to accomplish. For those non-Mac people out there, Keynote is Apple’s version of PowerPoint — a presentation software tool that comes with the iWork office suite. If you have a Mac and don’t use iWork, it’s well worth looking into. Many people find Keynote to be much better designed and easier to use than PowerPoint or any of the other presentation tools out there. The basic gist behind a lecture capture is that you are just using a presentation tool to give a normal presentation, and capturing the audio and the video that goes with it. This does not include any sort of writing on the board; I’ll deal with that in the next post in this series on “whiteboard” screencasts. But everyone should note well that the lecture capture approach is often part of my screencasts but rarely the entire thing. Many of my MATLAB screencasts are set up by brief, 1- to 2-minute long lecture captures before cutting away to a live screencast straight out of MATLAB. So even if lecture capture doesn’t sound like your thing, it’s worth thinking about. With Keynote, doing a lecture capture screencasts is very easy. After planning it out, you just make the slide deck exactly as you would if you were to present it live. Then, instead of clicking the “Play” button to do the slideshow, click on Play > Record Slideshow: This put the slideshow into presentation mode on your screen but also record audio from the microphone at the same time. From here, you just go through your slideshow as you would normally, and whatever goes into the mic gets recorded. When you’re done recording, go to Share > Export…: There’s an option on the screen that comes up next to export to Quicktime, and that’s what to select. (I use the default video/audio options; you can tweak these.) And presto — you have a nice, high-quality Quicktime movie of your lecture that’s suitable for sharing online or burning to a disc. PowerPoint (at least the version I have, which is PowerPoint 2008 for the Mac) has all of these capabilities as well. In PowerPoint, you would make up your slide deck as usual and then go to Slide Show > Record Narration…: What happens next is a bit different from Keynote. PowerPoint does what it says: It attaches an audio narration to each slide as you click through it in presentation mode. There is the option — but not a requirement — to record the timing of the slide transitions as well. In Keynote, the transitions are automatically timed. To turn this voiceover-plus-presentation into a movie, just go to File > Save as Movie… and there are plenty of options to choose from. I should mention that as for a microphone, I just use the built-in microphone on my Macbook Pro. I have used a USB headset microphone before and I think it did improve the audio quality noticeably, but to be honest with you: I’m really cheap. If I can get good audio quality that nobody complains about using the built-in mic, why spend$50 to get very good audio quality with a USB mic? One of these days I’ll break down and buy one, I’m sure. Until then I pinch my pennies.

There are a couple of issues to think about at this point regarding lecture captures.

• What if you want to use some other presentation tool besides Keynote or PowerPoint, for example the Beamer package for $\LaTeX$, or Prezi?
• What if you wanted to record portions of a lecture at a time and stitch them all together later, or conversely what if you wanted/needed to edit out or enhance portions of a lecture capture you created with Keynote or PowerPoint?

For those kinds of tasks, I would turn to my #1, go-to tool for almost all my screencasting needs: Camtasia for Mac. Camtasia is an all-purpose video and screencasting tool that does an outstanding job with just about anything I could possibly want to do with a basic screencast. There’s so much to Camtasia, and we are going to need to refer to it so much in later posts about whiteboard and demo screencasts, that I’m going to deal with Camtasia (and its alternatives) in a separate post.

Meanwhile, if you have other tricks and tips about lecture capture screencasting, please share in the comments.

Filed under Apple, Camtasia, Screencasts, Technology

## How I make screencasts: Chapter 0

Since I started to put serious amounts of time and effort into screencasting last summer, I’ve gotten a lot of requests to blog about how I go about making these things. Starting with this post, I’m going to do a multi-part series here about making screencasts — or at least how I make screencasts, which is a long way from perfect or canonical, but it’s what people asked for! I hope it’s useful for people who are interested in this kind of thing and need some pointers; and I hope too that those with more experience and better ideas than I have can share.

First, let’s start with a few FAQ’s.

Q: What is a screencast?

A: A screencast is a video of stuff that is happening on your computer screen. There is often, but not always, some kind of voiceover happening in the background as well. So a screencast can be a lot of different things: A recorded Prezi or PowerPoint slide presentation; a demo of computer software; a “whiteboard” lecture with audio capture; a video of you playing Angry Birds; or any linear combination of these.

Q: What’s the point of a screencast?

A: I suppose you could do just about anything with a screencast, but mainly the point is to instruct. Some people make short screencasts to show a remote collaborator or student how to do some little task on their computer, like this one I made on the fly in Linear Algebra class last Thursday morning to show students how to get MATLAB to produce $\LaTeX$ code. Or you can record partial or entire lectures (like many of the ones I did for my department’s YouTube channel) for students to watch outside of class. Or you can record lengthy demos of software usage like I have done in my ongoing series of MATLAB screencasts. Or you can record every level of Angry Birds you play. Suit yourself.

The screencast is just a means of conveying some process or stream of information that can be represented on the screen and therefore captured using software and disseminated on the web. It’s a pretty much wide-open medium.

Q: So what kinds of software and hardware and other stuff do you use?

This is a good question, but at this point I have to stop the FAQ’s and explain why there are going to be multiple posts in this series. I have a toolbox of software and hardware items that I use, but the exact combination that I use depends on the kind of screencast that I am trying to make. Basically, there are three different kinds of screencasts that I make:

• Lecture capture screencasts, where I am going through a Prezi or slide deck and giving audio narration;
• Whiteboard screencasts, where I am using an input device to hand-write things on the screen so that it looks like a typical whiteboard presentation; and
• Demo screencasts, where I am doing a straight-up screen capture of something happening on my computer (as opposed to a presentation or “whiteboard” work) in real time.

Each of these kinds of screencasts requires a different set of software and hardware tools, as well as a different set of approaches for actually making them. So I’m going to spend at least one post on each. Actually, most of my screencasts are really combinations of these; for example a lot of the MATLAB screencasts start and end with a lecture capture and have MATLAB demos in the middle.

In the next post, I’ll start things off by focusing on lecture capture screencasts and how I work with those. They’re probably the simplest of the three kinds I make.

Do you have any specific question or topic you’d like me to address as part of this series?

Filed under Inverted classroom, Profhacks, Screencasts, Teaching, Technology

## This week in screencasting: The polar express

It’s been a little quiet on the screencasting front lately, but in the next couple of weeks my colleague teaching Calculus III will be hitting material for which I volunteered to provide some content: namely, using MATLAB to visualize some of the surfaces and solids used in multiple integration. Yesterday, I finished two of these. The first on is on polar coordinates and polar function plotting in MATLAB:

And the second one is on cylindrical coordinates and plotting two-variable functions in cylindrical coordinates:

MATLAB doesn’t provide a built-in function for plotting in cylindrical coordinates. Instead — and this is either ingenious or annoying depending on how you look at it — to plot something in cylindrical coordinates, you generate all the points you need in cylindrical coordinates and then use the pol2cart function to convert them en masse to cartesian coordinates, then plot the whole thing as usual in cartesian coordinates.

I think this is smart, since by avoiding the use of a specialized function for cylindrical plots and sticking instead to a single command for 3D plotting, you learn one command for all 3D plots and you get to use all the extras available, such as adding a contour plot onto the cylindrical plot. Overloading the pol2cart function so that it can accept and produce the third coordinate makes this all work. Overall I like how MATLAB doesn’t try to make a function for everything but rather creates a well-featured set of relatively simple tools that will do lots of things.

But I can see where some people — especially MATLAB novices — would find all this annoying, since the entire process takes several steps. There’s a workflow diagram for doing this in the screencast, but a better way is to make an M-file that holds all the steps. Here’s the one I flashed briefly at the end of the screencast:


% Script for plotting a cylindrical function.
% Written by Robert Talbert, Ph.D., 10/20/2010

% Theta: Change t1 and t2 to set the starting and ending values for theta.
t1 = 0;
t2 = pi/2;
theta = linspace(t1, t2);

% r: : Change r1 and r2 to set the starting and ending values for theta.
r1 = -5;
r2 = 5;
r = linspace(r1, r2);

% Create meshgrid for inputs:
[theta, r] = meshgrid(theta, r);

% Apply the function to create a matrix of z-values. Change the function to
% match what you want to plot.

z = r*cos(theta);

% Convert to cartesian and plot using mesh:

[x,y,z] = pol2cart(theta, r, z);
mesh(x,y,z)


It would be simple enough to modify this so that it’s a function rather than a script, accepting the arrays theta and r and a function handle for z, and then producing the 3D plot. Or, one could even make an “ez” version where the user just enters a string containing the function s/he wants. If somebody wants to try that out, and you want to share your results, just put the source code in the comments.

The third one in this series will be up later this weekend. It’s on spherical coordinates and it’s pretty much the same process, only using sph2cart instead of pol2cart. There might be a fourth one as well, dealing with some special cases like constant cylindrical/spherical functions (you can’t just say “rho = 5”, because rho has to be a matrix) and how to plot not just the surfaces but the volumes underneath them.

Comments Off on This week in screencasting: The polar express

Filed under Calculus, Engineering, Math, MATLAB, Teaching, Technology

## This week (and last) in screencasting: Functions!

So we started  back to classes this past week, and getting ready has demanded much of my time and blogging capabilities. But I did get some new screencasts done. I finished the series of screencasts I was making for our calculus students to prepare for Mastery Exams, a series of short untimed quizzes over precalculus material that students have to pass with a 100% score. But then I turned around and did some more for my two sections of calculus on functions. There were three of them. The first one covers what a function is, and how we can work with them as formulas:

The second one continues with functions as graphs, tables, and verbal descriptions:

And this third one is all on domain and range:

The reason I made these was because we were doing the first section of the Stewart calculus book in one day of class. If you know this book, you realize this is impossible because there is an enormous amount of stuff crammed into this one section. Two items covered in that section are how to calculate and reduce the difference quotient $\frac{f(a+h) - f(a)}{h}$ and doing word problems. Each of these topics alone can cover multiple class meetings, since many students are historically rusty or just plain bad at manipulating formulas correctly and suffer instantaneous brain-lock when put into the presence of a word problem. So, my thought was to go all Eric Mazur on them and farm out the material that is most likely to be easy review for them as an outside “reading” assignment, and spend the time in class on the stuff that on which they were most likely to need serious help.

Our first class was last Tuesday and the second class wasn’t until Thursday, so I assigned the three videos and three related exercises from the Stewart book for Thursday, along with instructions to email questions on any of this, or post to our Moodle discussion board. I made up some clicker questions that we used to assess their grasp of the material in these videos, and guess what? Many students didn’t have any problems at all with this material, and those who did got their issues straightened out through discussions with other students as part of the clicker activity.

They’ll be assessed in 2 or 3 other ways on this stuff this week to make sure they really have the material down and are not just being shy about not having it. But it looks like using screencasts to motivate student contact with the material outside of class worked fine, at least as effectively as me lecturing over it. And we had more time for the hard stuff that I wouldn’t expect students to be able to handle, not all of them anyway.

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## This week in screencasting: Contour plots in MATLAB

By my count, this past week I produced and posted 22 different screencasts to YouTube! Almost all of those are short instructional videos for our calculus students taking Mastery Exams on precalculus material. But I did make two more MATLAB-oriented screencasts, like last week. These focus on creating contour plots in MATLAB.

Here’s Part 1:

And Part 2:

I found this topic really interesting and fun to screencast about. Contour plots are so useful and simple to understand — anybody who’s ever hiked or camped has probably used one, in the form of a topographical map — and it was fun to explore the eight (!) different commands that MATLAB has for producing them, each command producing a map that fits a different kind of need. There may be even more commands for contour maps that I’m missing.

I probably won’t match this week’s output next week, as I’ll be on the road in Madison, WI on Monday and Tuesday and there are several faculty meetings in the run-up to the start of the semester. But at the very least, I need to go back and do another two-variable function plot screencast because I inexplicably left off surface plots and the EZMESH and EZSURF commands on last week’s screencasts.

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Filed under Calculus, Educational technology, Math, MATLAB, Screencasts, Technology

## This week in screencasting: Making 3D plots in MATLAB

I’ve just started on a binge of screencast-making that will probably continue throughout the fall. Some of these screencasts will support one of my colleagues who is teaching Calculus III this semester; this is our first attempt at making the course MATLAB-centric, and most of the students are alums of the MATLAB course from the spring. So those screencasts will be on topics where MATLAB can be used in multivariable calculus. Other screencasts will be for my two sections of calculus and will focus both on technology training and on additional calculus examples that we don’t have time for in class. Still others will be just random topics that I would like to contribute for the greater good.

Here are the first two. It’s a two-part series on plotting two-variable functions in MATLAB. Each is about 10 minutes long.

Part of the reason I’m doing all this, too, is to force myself to master Camtasia:Mac, which is a program I enjoy but don’t fully understand. Hopefully the production value will improve with use. You’ll probably notice that I discovered the Dynamics Processor effect between the first and second screencasts, as the sound quality of Part 2 is way better than that of Part 1. I’d appreciate any constructive feedback from podcasting/screencasting or Camtasia experts out there.

I’m going to be housing all these screencasts at my newly-created YouTube channel if you’d like to subscribe. And if I manage to do more than one or two a week, I’ll put the “greatest hits” up here on the blog.

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Filed under Calculus, Camtasia, Screencasts, Teaching, Technology, Textbook-free