bevin - Developer IT

Rainbows and Unicorns at the Devoxx OTN Hack Fest

- by Tori Wieldt

At the OTN Hack Fest at Devoxx, several developers did their first "hello world" with the Internet of Things (IoT). They had fun and built basic applications with Java Embedded, Raspberry Pi and Leap Motion controllers. Experts Yara & Vinicius Senger and Geert Bevin provided the basics and support. Geert Bevin did a bit of hacking too. Check out this video to see what he came up with a short amount of time: &amp;amp;amp;lt;span id=&amp;amp;amp;quot;XinhaEditingPostion&amp;amp;amp;quot;&amp;amp;amp;gt;&amp;amp;amp;lt;/span&amp;amp;amp;gt; Learn more about Java Embedded at the Oracle Technology Network.

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Hack Fest Going Strong!

- by Yolande Poirier

Today was the first day of the Hack Fest at Devoxx, the Java developer conference in Belgium. The Hack Fest started with the Raspberry Pi & Leap Motion hands-on lab. Vinicius Senger introduced the Java Embedded, Arduino and Raspberry Pi. Java Champion Geert Bevin presented the Leap Motion, a controller sensing your hands and fingers to play games by controlling the mouse as an example. "Programmers are cooler than musicians because they can create entire universe using all senses" explained Geert In teams, participants started building applications using Raspberry Pi, sensors and relays. One team tested the performance of Tomcat, Java EE and Java Embedded Suite on the Raspberry Pi. Another used built an text animation using a LCD screen. Teams are using the Leap Motion to close and open programs on the desktop and other teams are using it as a game control.

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Normalize FFT magnitude to imitate WMP

- by Bevin

So, I've been working on a little visualizer for sound files, just for fun. I basically wanted to imitate the "Scope" and "Ocean Mist" visualizers in Windows Media Player. Scope was easy enough, but I'm having problems with Ocean Mist. I'm pretty sure that it is some kind of frequency spectrum, but when I do an FFT on my waveform data, I'm not getting the data that corresponds to what Ocean Mist displays. The spectrum actually looks correct, so I knew there was nothing wrong with the FFT. I'm assuming that the visualizer runs the spectrum through some kind of filter, but I have no idea what it might be. Any ideas?

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Convert Pen to IntPtr

- by Bevin

Is there a simple way to convert a System.Drawing.Pen into its unmanaged counterpart? Like, if you had a Pen like this: Pen p = new Pen(Color.Blue, 1f); IntPtr ptr = p.ToPtr(); I know this code doesn't work, but is there a way to do it similarly?

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Adding scrollbars to UserControl

- by Bevin

I am trying to add vertical and horizontal scrollbars to my UserControl with the HorizontalScroll and VerticalScroll properties, but I am having extreme issues. My problem arises when I drag or manipulate the scroll box on the bar. When I let it go, it simply jumps back to the start position! I know of the AutoScroll property, but I do not want to use it since I want to be able to control every aspect of my scrollbars, and I don't want it to be done automatically. Also, according to the documentation, AutoScroll is for "[enabling] the user to scroll to any controls placed outside of its visible boundaries" which isn't what I want. I just want scrollbars. ...aaand I suppose I could add VScrollBar and HScrollBar to the control, but why should I do this when the scroll functionality already exists? Seems like a waste to me.

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Collision detection by sliding against a plane in XNA

- by Bevin

Hello, I am attempting to engineer a collision detection algorithm for a custom Minecraft client I'm making. Basically, the entire world is made up of cubes, and the player (or camera) needs to be able to stand on and move against these cubes. The result I want is illustrated in this image: The green line is the player's movement vector. When the player is brushing up against a plane of one of the cubes, I want the vector to change to one that is perpendicular with the plane. The vector should, however, keep all of it's velocity in the plane's direction, yet lose all velocity towards the plane. I hope I've made my question clear. What is the best and most efficient way to implement a collision detection system like this? Also, will a system like this allow for a simple gravity component?

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Issue with transparent texture on 3D primitive, XNA 4.0

- by Bevin

I need to draw a large set of cubes, all with (possibly) unique textures on each side. Some of the textures also have parts of transparency. The cubes that are behind ones with transparent textures should show through the transparent texture. However, it seems that the order in which I draw the cubes decides if the transparency works or not, which is something I want to avoid. Look here: cubeEffect.CurrentTechnique = cubeEffect.Techniques["Textured"]; Block[] cubes = new Block[4]; cubes[0] = new Block(BlockType.leaves, new Vector3(0, 0, 3)); cubes[1] = new Block(BlockType.dirt, new Vector3(0, 1, 3)); cubes[2] = new Block(BlockType.log, new Vector3(0, 0, 4)); cubes[3] = new Block(BlockType.gold, new Vector3(0, 1, 4)); foreach(Block b in cubes) { b.shape.RenderShape(GraphicsDevice, cubeEffect); } This is the code in the Draw method. It produces this result: As you can see, the textures behind the leaf cube are not visible on the other side. When i reverse index 3 and 0 on in the array, I get this: It is clear that the order of drawing is affecting the cubes. I suspect it may have to do with the blend mode, but I have no idea where to start with that.

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Separate groups of objects based on their properties

- by Bevin

I want to separate an array of my custom object into several arrays, based on the values of their two properties. The struct looks like this: struct MyStruct { public string Person { get; set; } public string Command { get; set; } } Now, if I have an array with a few objects: {Person1, cmd1} {Person1, cmd3} {Person2, cmd3} {Person3, cmd2} {Person2, cmd4} I want to be able to place them into one array for each person, that lists all of the commands for that person: {Person1: cmd1, cmd3} {Person2: cmd3, cmd4} {Person3: cmd2} I hope I've made it clear with my descriptions. I would assume that there is an elegant way to do this with LINQ, but I have no idea where to start.

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Using DynamicVertexBuffer in XNA 4.0

- by Bevin

I read about DynamicVertexBuffer, and how it's supposed to be better for data that changes often. I have a world built up by cubes, and I need to store the cubes' vertices in this buffer to draw them to the screen. However, not all cubes have vertices (some are air, which is transparent) and not all faces of the cubes need to be drawn either (they are facing each other), so how do I keep track of what vertices are stored where in the buffer? Also, certain faces need to be drawn last, namely the ones with transparency in them (like glass or leaves), and these faces also need to be drawn in a back-to-front order to not mess up the alpha blending. If all of these vertices are stored arbitrarily in this buffer, how do I know what vertices are where? Also, the number of vertices can change, but the DynamicVertexBuffer doesn't seem very dynamic to me, since I can't change it's size at all. Do I have to recreate the buffer every time I need to add or remove faces?

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Hack Fest at Devoxx

- by Yolande Poirier

On November 11th and 12th, Devoxx attendees will get the chance to build a Java embedded application onsite. During the Raspberry Pi & Leap Motion hands-on labs on Monday and Tuesday mornings, you will learn about Raspberry Pi development with Java embedded using Leap Motion and other sensors. The afternoons are hacking time on a project of your choice. You can get your inspiration from existing projects. You can also use their project source code and improve on already developed applications. The goal is for you to create something fun and innovative in only a couple of days, no matter your experience in embedded systems. We provide you with equipment like the Raspberry Pi, sensors, and Leap Motion. Thanks to Stephan Janssen for lending us 10 Leap Motions for the Hack Fest. Raspberry Pi and sensors are pre-configured. You will access the sensors via a web address. You can build a project alone if you want. We also give the opportunity to brainstorm ideas with other attendees and maybe build something more complex. You will get one-on-one help from top-notch coaches. Vinicius Senger has tons of experience with Java and the Raspberry. He runs Java embedded challenges and give training year round. Geert Bevin contributed to many open source projects and his latest venture is with the Leap Motion. Bruno Borges's expertise is in connecting backend logic with great interfaces. Yara Senger is a Java Champion and a great Java embedded mentor. Don't miss this opportunity! This is your chance to transform your idea into a Raspberry Pi or a Leap Motion application.

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So Much Happening at Devoxx

- by Tori Wieldt

Devoxx, the premier Java conference in Europe, has been sold out for a while. The organizers (thanks Stephan and crew!) cap the attendance to make sure all attendees have a great experience, and that speaks volumes about their priorities. The speakers, hackathons, labs, and networking are all first class. The Oracle Technology Network will be there, and if you were smart/lucky enough to get a ticket, come find us and join the fun: IoT Hack Fest Build fun and creative Internet of Things (IoT) applications with Java Embedded, Raspberry Pi and Leap Motion on the University Days (Monday and Tuesday). Learn from top experts Yara & Vinicius Senger and Geert Bevin at two Raspberry Pi & Leap Motion hands-on labs and hacking sessions. Bring your computer. Training and equipment will be provided. Devoxx will also host an Internet of Things shop in the exhibition floor where attendees can purchase Arduino, Raspberry PI and Robot starter kits. Bring your IoT wish list! Video Interviews Yolande Poirier and I will be interviewing members of the Java Community in the back of the Expo hall on Wednesday and Thursday. Videos are posted on Parleys and YouTube/Java. We have a few slots left, so contact me (you can DM @Java) if you want to share your insights or cool new tip or trick with the rest of the developer community. (No commercials, no fluff. Keep it techie and keep it real.) Oracle Keynote Wednesday morning Mark Reinhold, Chief Java Platform Architect, and Brian Goetz, Java Language Architect will provide an update on Java 8 and beyond. Oracle Booth Drop by the Oracle booth to see old and new friends. We'll have Java in Action demos and the experts to explain them and answer your questions. We are raffling off Raspberry Pi's each day, so be sure to get your badged scanned. We'll have beer in the booth each evening. Look for @Java in her lab coat. See you at Devoxx!

Developer IT