Stuff I'm working on at the moment

Posts by Eddie Long

Writing a game engine – Day 1

Apr14
2011 2 Comments Written by Eddie Long

Ok so I’ve decided to write my own engine. I’m doing this not to make a game or anything but to learn from it. I’ve read the articles where people say ‘make a game not an engine’ but I think it is very important to actually learn by doing. I’ve been reading a lot recently and feel like a lot of the stuff almost goes in one ear and out the other, mainly because I’m not actually doing anything to follow up my learnings.
So I’m going to begin creating an C++ Open GL based engine (over my lunchtime). The main aims are:

  • Minimise the use of virtual functions and inheritance
  • Minimise the use of STL
  • Have modular and heavily configurable sub-systems
  • Aim for deferred rendering in my scene
  • Implement a simple data-based GUI that includes an in-game editor (possibly haven’t decided on this yet)
  • Incorporate scripting
  • Make use of threading/multi cores

Today I’m not really doing anything in particular, just reading. I’d imagine I’ll be doing this for a while before I even write a line of code.

I’ve read the excellent Game Engine Architecture by Jason Gregory but will start again looking at it taking real note and actually sketching out some designs. I like the idea of the way Unity do things with Entities and a property system.

I intend to revisit this post during the coming months and amend, laugh and update it… will be an interesting challenge ahead. It’s certainly going to take a long time given that I can only give it about 45 minutes a day!

Posted in C/C++

Perforce checkin email notification

Apr05
2011 1 Comment Written by Eddie Long

Quickie today, if you want to be emailed every time someone checks in something to a particular section of the depot you can do this quite easily using the p4 client.

Go to Connection->Edit Current User and click on the ‘Reviews’ tab. Here you’ll see the depot view. Navigate to the topmost section that you want to receive emails from, right click it and select Include Tree. You can also specify the section(s) of the depot you want to review by manually entering a path in the first tab, but if theres a nice pretty GUI there to do it, why bother manually entering paths?!

Posted in Perforce - Tagged

Visual Studio filters disappear

Apr04
2011 1 Comment Written by Eddie Long

Recently I had a project in VS2008 whereby all my filters disappeared and all files appeared unfiltered. Very annoying when trying to locate files, I thought something was borked with the vcproj or even the solution. The fix is actually really simple, somehow (I have no idea how) the ‘Show All Files’ option had been toggled. To untoggle it go and click Project->Show All Files. Very simple I know but it had me perplexed for a couple of minutes!

Posted in C/C++, Visual Studio

Perforce with C# (p4 dotnet)

Mar25
2011 Leave a Comment Written by Eddie Long

I’ve found a need to use Perforce with C# recently. The first step was to get the right DLLs for the job. I got the P4 API DLL from SourceForge here

Extracting it, I think you actually only need the p4API dll in the bin/CLR_2.0 directory, I took the whole directory just in case.

In your project right click on the References directory and ‘Add Reference’ and navigate to the p4api.dll. 

// Load up the API
using P4API;
...

// Create the connection
P4Connection p4 = null;
            try
            {
                p4 = new P4Connection(); // Uses the default connection to Perforce
                p4.Connect();

                // Don't throw an exception on a Perforce error.  We handle these manually.
                p4.ExceptionLevel = P4ExceptionLevels.NoExceptionOnErrors;
            }
            catch (System.Exception ex)
            {
                Console.WriteLine(ex.Message);
            }

I want to delete a file from the repository so to do this I needed to just put through the right call. From what I’ve gathered you can run any P4 command that can be run via the command line, all you need to do is

try
{
       if (p4 != null)
       {
             p4.RunUnParsed("delete", selectedItemPath);
       }
}
catch (System.Runtime.InteropServices.COMException ex)
{
        MessageBox.Show(ex.Message);
}

Done!

Posted in C/C++ - Tagged ,

C# Npgsql tutorial

Mar24
2011 Leave a Comment Written by Eddie Long

Hi,

I’ve just started using C# for the first time and decided to chuck up a little intro on how to connect with a Postgres database. This is a very stripped down tutorial, does the basics and doesn’t really handle exceptions, error states and the like. Firstly you need to get a few DLLs, Npgsql.dll, policy.2.0.Npgsql.dll and MonoSecurity.dll. You can get them from PgFoundry here.

I’ve put these in the same folder as the project. Go to Solution Explorer and locate the ‘References’ section under your project. Right click that and Add Reference. Click the ‘Browse’ tab and select the Npqsql dll only.
Firstly you need to load up the package/namespace (I’m not sure of the correct terminology here). Then you’re ready to connect to the database using the correct name, port, username and so on. This is simple.

using System;
...
using Npgsql;

....

NpgsqlConnection dbConnection = new NpgsqlConnection("Server=myServer;Port=xxxx;User Id=xyz;Password=xyz;Database=myDB;");

try
 {
        dbConnection.Open();
 }
catch
{
        //Handle error states here
}

That’s it! You’re now ready to execute queries and updates on the database.

I’ve included a very simple select statement below, it selects all from a hypothetical animal table and extracts the name and type column values from the results. The GetOrdinal is a useful helpful function to return you the integer that represents the index of the named column. It is more robust to changes in the database as indices may change but you need to check for NULLs as it won’t work (I’ve found out!)

NpgsqlCommand Command = new NpgsqlCommand("select name,type from animals", dbConnection);
NpgsqlDataReader result = Command.ExecuteReader();

while (result.Read())
{
      String animalName = result.GetString(result.GetOrdinal("name"));
      String animalType = result.GetString(result.GetOrdinal("type"));
      ... (Do something here)
}

Finally when you’re done with your database you need to close down the connection

dbConnection.Close();
dbConnection = null;

Thats it’s some very simple DB manipulations in very few lines of code, impressed with C# so far I must say!
Next step do things in transactions and handle exceptions!

Posted in C#, C/C++ - Tagged , ,

warning C4541: ‘dynamic_cast’ used on polymorphic type ‘xyz’ with /GR-; unpredictable behavior may result

Feb17
2011 Leave a Comment Written by Eddie Long

I got this error today in Visual Studio when building our game at work.
I was trying to go a harmless dynamic_cast to downcast and object to a derived object and was confronted with this problem. After looking up the error it seems that it can be made to go away by turning on RTTI which is something we do not want to do due to the overhead of it and we have our own reflection system anyway and the type information isn’t required from RTTI. The reason being that dynamic_cast makes use of typeid which is only available under RTTI enabled projects.

I could have done a static_cast but didn’t want to do this blindly. Also not being a fan of ‘unpredictable behaviour’ I instead had to resort to a old fashioned dangerous C-style cast e.g.

     MyObject* pObj = (MyObject*)pObjectToCast;

This works fine, gets rid of the warning but I don’t like it.

Posted in C/C++

Hundreds of errors including: Expected declaration specifiers or ‘…’ before ‘CFXMLTreeRef’

Jan05
2011 1 Comment Written by Eddie Long

Hi,

I upgraded recently to XCode 4.2 and on building the release version of my app was getting 96 odd errors. All of these orginate from Foundation.h with a callstack like below

/Users/parrotbait/Documents/Dropbox/
/myApp/myApp_Prefix.pch

/Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/Foundation.h:81:0 In file included from /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/Foundation.h

/Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSURLError.h:17:0 In file included from /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSURLError.h

/Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/CoreServices.framework/Headers/CoreServices.h:29:0 In file included from /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/CoreServices.framework/Headers/CoreServices.h

/Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/CoreServices.framework/Frameworks/OSServices.framework/Headers/OSServices.h:54:0 In file included from /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/CoreServices.framework/Frameworks/OSServices.framework/Headers/OSServices.h

/Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/CoreServices.framework/Frameworks/OSServices.framework/Headers/WSMethodInvocation.h:773:0 Expected declaration specifiers or '...' before 'CFXMLTreeRef' in /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/CoreServices.framework/Frameworks/OSServices.framework/Headers/WSMethodInvocation.h

Why were the OSX frameworks being used? As they were being used for an iOs build there was all sorts of problems. So I began to hunt down the origin of the call to the OSX headers.
After checking my project settings everything looked fine and I couldn’t see what the problem was. However after opening the transcript of the build I saw that on compiling the precompiled headers I was the errors were occuring. There was a compiler flag ‘-F’ for framework that indicates what paths to search for frameworks:

-F/Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks

Right clicking on my Target and searching for Framework in the build section, I found that I had somehow (although I don’t remember doing this and am not convinced I really did) had an entry for ‘Framework Search Paths’

"$(DEVELOPER_DIR)/SDKs/MacOSX10.6.sdk/System/Library/Frameworks"

Removing this got rid of my 100s of build errors.

Posted in iPhone, iTouch, Objective C

Visual Studio – No files were found to look in. Find was stopped in progress.

Dec13
2010 Leave a Comment Written by Eddie Long

This is the weirdest thing, I was working away in Visual Studio 2008 when I attempted a global search and it failed indicating that ‘No files were found to look in. Find was stopped in progress.’. The weird thing is that I had selected Entire Solution and it should have worked. After some quick googling I found out that other people have had the same problem. Although the reason for it happening hasn’t been entirely explained (nor do I really care) the solution is as follows:

In VS2008 press Alt + Break to make find work again
In VS2005 press Ctrl + Scroll Lock (I haven’t tried this one)

Find works again, hurray!

Posted in C/C++

Get Windows folder path

Dec10
2010 Leave a Comment Written by Eddie Long

It is quite easy to find a path to a particular folder in Windows, a function called SHGetFolderPath exists that will return you the user’s file system path to common system locations such as My Documents, Program Files, My Music, App Data and so on. I wanted to get the system font folder path so this function proved especially useful. Usage is as below:

Requirements: Add shell32.lib to your linked in libraries. 

#include 
#include 

TCHAR strPath[ MAX_PATH ];

if (FAILED(SHGetSpecialFolderPath(
	0,       // Hwnd
	strPath, // String buffer.
	CSIDL_FONTS, // CSLID of folder
	FALSE ))) // Create if doesn't exists?
{
	//SOMETHING HAS GONE WRONG
}

Works a treat
WARNING: This function is supported from Windows 2000 Server onwards, if you need to support these OSes you may need to use something else.

Posted in C/C++

PrintF wide format specifier

Nov15
2010 Leave a Comment Written by Eddie Long

Today I ran into the problem whereby printf was putting junk into a string even though it was using %s. A little perplexed about it I had a look around and saw that there is a separate format specifier that expects a wide string. My application is not compiled in Unicode but I require a wide string at this point.

So 

wsprintf(buffer, L"Name %s", myWideCharString)

The above code wouldn’t work. However if I use the code below it would

wsprintf(buffer, L"Name %lS", myWideCharString)

The reason being that printf does some behind the scenes conversion and %s or %S will convert to a char*. %lS tells it that what is coming in is a wide string and to handle it as such.

I also found out that %f doesn’t work with wsprintfW, wierd and quite silly really.

Posted in C/C++
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