Learning OpenGL. Log 3

This post is part of a series of logs of my journey in learning OpenGL (or as some say, modern OpenGL).

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I’ve started an other log, dedicated for the engine project, so I won’t talk about it any more here unless it’s very cool or related.

Today I worked with the glm library a bit more and wrote a TransformationMatrix class.

A very simple class. The name is a bit deceiving. The entire class is actually compose of 4 glm::mat4 objects. 3 for the basic transformations, and the final one being the product of the other 3. The comments are a bit incomplete but you can probably tell what the member functions do already. There are 3 setter methods, for scaling, translation and rotation. There are also two getter methods for getting the final transformation matrix.

What interesting here is that, at the moment the final transformation matrix is only evaluated when it needs to be re-evaluated. Calling any of the setter methods will not trigger the evaluation, but they will m_Evaluated to false. When the getter methods are called. They will re-evaluate the final transformation matrix only if it’s been previous modified.

There are no methods such as TranslateFromCurrentPos or RotateFromCurrentAngle at the moment because I believed those should be implemented in a entity class which will compose one or multiple TransformationMatrix in the render component. This will allow me to implement higher level movement stuff on top while keeping the matrix class lightweight and encapsulated.

Here’s the cpp part of the class:

Of course. The class is incomplete. I will overload some operators for matrix multiplication and what not. At the moment I have to call “GetGLMMatrix()” to pass the matrix to my ShaderProgram class. I will need to add support for this new class into my shader code.

I will begin work on a camera class next, once I’m up to date with this week’s lab work.

Learning OpenGL. Log 1

This is the first, in what will be a series of posts on my journey in learning OpenGL (or as some say, modern OpenGL).

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It’s been 2 weeks since Uni started. As I am doing an Interactive Computer Graphics this semester, which uses OpenGL. I have therefore, started it.

Besides learning to draw the basic primitives and the usual rainbow colored triangles. Plus a little bit of shader programming. I’ve spent a lot of the time in the past 2 weeks just playing and experimenting with a couple of utility tool kits and  graphics libraries for window creation and input handling. Namely Freeglut, GLFW, and SFML. Today, I will talk about my experience with them so far, and what not.

From a beginner point of view, getting started with learning how to setup a basic window and OpenGL context up was such a pain. Going from a C++ programmer to using libraries/API’s that are written in C also made me quite uncomfortable. To those who are a novice like me. Fear not, you will get used to it after a while. The hardest part is actually just getting the few concepts down.  Specifically window and context initialization and the way OpenGL’s API is defined. This is not a tutorial, so I won’t go into the details, but I will provide a list of the online tutorials I’ve been using that are very good.

Freeglut (Wiki link)

Freeglut is an API compatible clone of the now obsolete Glut. It is under active development, where as work on Glut halted back in 2005. All it does is providing means to create a window which an OpenGL context will be attached to. The reason I took a dip into Freeglut is because the Interactive Computer Graphics unit uses it (because the text book uses it…). It has been the de facto choice for tutorials and teaching materials, even though it should just die after the original project halted. now Just a quick rank: the lecturer seems like a nice guy, but he is just NOT lecturer materials. The textbook that he chose is also horrible. From what I’ve gathered, the same textbook has been used for the last couple years for this unit, which is sad. The text attempts to teach theories and concepts in computer graphics and tries to mix OpenGL into it.

The way Freeglut/Glut works is by providing a couple callbacks for different things while keeping completely control over it’s own main loop. This is good for making applications like interactive graphics render and model viewers, application which it was designed for developing.  If you intend to develop applications such as games, that are much more interactive and resource intensive, then Freeglut is not for you. At first I wasn’t too sure why, but control over the main loop is very important.

To use Freeglut, you initialize the library and set your call backs, and then you begin Freeglut’s mainloop. At this point, Freeglut takes over control until it exits.

GLFW (link)

The next tool kit I tried is GLFW. It is a very minimal tool kit and does not do as much as what Freeglut give you, but it does give you control over your mainloop. Instead of entering Freeglut’s mainloop, you have something along the line of “pollevents()”, which it internally calls callbacks that can you set, just like Freeglut. GLFW and Freeglut are quite similar with their functions, in terms of initialization and configurating the window. I spent about a week on Freeglut. By the time I moved to GLFW, it wasn’t too hard picking it up.

What I did was I ended up wrapping the GLFW stuff into a RenderWindow class, and wrote a simple event queue and wrote custom callbacks to translate most of the call backs into my own events, which I then handled by polling my own event queue. I modeled it after SFML because I’ve been using it for a while now and the OOP aspect of it made it very elegant.

One thing that I do miss that Freeglut has and GLFW doesn’t is menu creation. Pop-up menus will be used extensively for this unit so I spent a lot of time investigating what alternative there is for GLFW besides writting my own. The problem is, there isn’t really any. I did managed to discover CEGUI, nui3, glui2 and AntTweakBar.  The AntTweakBar library seems like the easiest to implement with the others looking quite complicated. I did not give any of them a try so I could be wrong. What bothered me is that they were GUI/widget tool kits and do not provide the ‘traditional’ menu.

SFML (link)

Finally. I remember that  SFML uses OpenGL internally. SFML (short for simple, fast, multi-media library). It’s popular for creating 2D games and applications. Bit of a rival to SDL. Best of all, it’s written in C++, and under active development. The library provides a lot to developers with 5 different modules. Providing classes for not just handling 2D graphics, but there are also classes for handling audio, network and other things. SFML allows you to use the OpenGL API directly, and it’s very simple to do some. What’s nice is that you can use it’s 2D graphics module along side of it. There are quite a few GUI libraries built for SFML but I havn’t look too deep into yet. The best thing yet is that I’ve been using SFML for the last couple dozen weeks on my 2D game engine project.

I spent the afternoon today and extended the engine enough to get some basic OpenGL primitive drawn. The engine is no where near completion. If I could use SFML for the interactive computer graphics unit then I will have the opportunity to develop and grow the engine along side the course project, instead of pausing work on my game project.

Closing

This blog has turned out to be a lot more formal and a bit more longer than I expected, but that’s cool. In closing, the libraries I mentioned today are not all there is out there. They are simply the ones that I’ve discovered and explored so far. There are many more out there that can be used for creating window and OpenGL context. The ones that I could think of on top of my head are Qt and SDL. I’ve used Qt before and it’s awesome for lots of things.

The next thing I will do is work a bit more on OpenGL with SFML for a bit more, and do so by extending my engine. I will also have to contatct my unit coordinator to accquire permission on developing on VS2012 with SFML on Windows (the project is meant to be done on a POSIX system with Freeglut). Lastly, I will continue learning OpenGL.

Stay tuned for the next log. Peace out!

List of tutorials

(in order of most favored):

List of libraries mentioned

(no particular order):

  • Freeglut
  • GLFW
  • SFML
  • SDL
  • Qt
  • nui3
  • CEGUI
  • glui2
  • AntTweakBar

A quick guide to using Precompiled Headers (Visual Studio)

Precompiled headers can be a very useful thing. Increase productivity by saving time otherwise would have spent on compiling.

This is a quick guide on how to setup precompiled headers in Visual Studio (specifically VS2012). I’m not going to explain what it is, or why you might want it. So let’s go.

I will assume that you currently have a project that does not have precompiled headers setup but you want it now, or later down the road.

Win32_Application_Wizard

When you create a new project in Visual Studio, and you select a template such as the “Win32 Console Application” template. The Win32 Application Wizard will open and attempt to guide you through the basic configurations of the project. A tickbox is provided for if you want Precompiled header. This is not the case when you create an empty project. The Wizard simply does not appear.

To setup Precompiled Header. First create two source files: “stdafx.h” and “stdafx.cpp” (For the tinkers. It actually doesn’t matter what you name them.) , and add them to your projects.

solution_explorer

Now select all source files (your .cpp files) in the Solution Explorer, right click and hit Properties. The Property Page should pop up.

property_page

In the Property Pages, head to “Configuration Properties” – > “C/C++” -> “Precompiled Headers”. Change “Precompiled Header” to “Use (/Yu)”. Click “Apply” at the bottom right and click “OK” to close the page. Next, go back to Solution Explorer. Select and right click on the file “stdafx.cpp” (or whatever you named it), and click on “Properties” again. Navigate to “Configuration Properties” – > “C/C++” -> “Precompiled Headers” (again).

select_create

This time, change “Precompiled Header” to “Create (/Yc)”. Again, click “Apply” at the bottom right and click “OK” to close the page.

Lastly. Do your usual “#ifndef #define #endif” or “#pragma once” include guard inside the “stdafx.h” file, and include this file in EVERY single file inside your project. That’s right. Every single one of them. Now, rebuild your solution and it should be all good.

[code language=”cpp”]
#pragma once
#include "stdafx.h"
#include <iostream>
// etc …
[/code]

Remember that “#include “stdafx.h” ” must appear before every #include in every file. Otherwise the preprocessor/compiler will happily ignore anything before it and throw you errors.

That’s all. Hope this little guide will help those that were lost and confused like me.  Here’s a couple links that will explain what Precompiled Header is to some extent. It’s best to do your own Google foo on this topic.

http://en.wikipedia.org/wiki/Precompiled_header

http://www.ogre3d.org/tikiwiki/tiki-index.php?page=precompiled+headers

http://msdn.microsoft.com/en-us/library/szfdksca(v=vs.71).aspx

Bye for now.

C++

image

My dedication for the next two or few years.

It was funny when I’ve finally decided that I wanted to become a programmer, a software developer. The builder of something that is the glue of all trades in this digital world. It all seemed so long a go.

Being a programmer, fundamentally meant one thing. To speak one or multiple languages that are at the end of the day, just a bucket load of 1’s and 0’s. Not only that, but to express ideas freely and creatively using those languages. To cultivate innovations and revolutions. Kind of like a poet and his poems, except with programming languages.

I wasn’t sure which one to start with. Where to take my first step and dip my foot in without drowning and be forced to retreat like a coward. With the massive variety programming languages out there, I did not want to learn or know them all. It was clear that the mastery of one is better than minimal knowledge of a couple. I also desired the highest performance and the best flexibility without losing fine grain control and power. With the general trend shifting favour to scripting, dynamic languages and producing web applications instead of native ones. It seemed like lower level programming languages will soon become what some might call a forgotten art to the majority of the “developer” community. Especially with the ever decreasing difficulty in application development with the newer high level programming languages.

At the end, I chose C++. I’ve decided to tame this beast and master it with all I can.

Was this the right decision? Is this a good investment?
Only time will tell.

BenH