C++ for Gaming & Computer Graphics (Handbook)

⚠️ Disclaimer: The following my personal notes in C++ fundamentals for game programming and computer graphics. It does not intent to be a formal guidance for third-parties, use it under your responsibility.

Description

C++ is a general purpose, mid-level programming language, very popular for video game and computer graphics development.

Like Java, it supports Object-Oriented Programming. It is a compiled language, which means that the compiler takes source c++ code and creates binary code. The same source code will compile in several OS*, and is highly customisable, so it might happen that similar written code might have different behaviour between developers.

Notice that is easy to write unsafe C++ code; naively C++ is slower than naive Java, because C++ allows the developer to manages it’s own memory. Also, 0 could be many things: pointer, bool, an int. Hence, it is crucial to be aware how the variables and the memory if use along the program.

What’s the main.cpp file?

All C++ program has a main.cpp file with a int main() function that starts the application. The program returns zero if it runs until completion.

int main (int argc, char * argv[])
{
	sdt::cout << "Hello, world! \n";
	return 0;
}

C++ Standard Library std::

Collection of code (clases and functions) available for devs to use. Offers useful functionally like Strings, IO, files, vectors, set, map, and algorithms like sorting and others. One need to reference the library with the namespace std:: . The namespace encapsules code, like std::string or std::vector .

File name convention

./program_folder
	|─ main.cpp
	└─ main.h

Why do we need two files main.cpp main.h?

Classes are separated into two files:

Headers files .h: Use for function and class declarations.

• Separating design form implementation 💙: Allows developers quickly see all functionality of a class without going through the entire definition. One need to declare function name, return type, arguments type.

  class SpaceShip
  {
  	public:
  	
  	float posX;
  	float posY;
  	
  	void shot();
  	void destroy();
  	// and much more without getting into the details
  }

  In the compilation process, if the header file changes, all the sources files using that class will re-compile. But if the source file changes, it does not affect it dependencies.

  ⚠️ Problematic with cyclic dependencies error.

Source files .ccp: Use for function and class definitions (implementations).

• C++ requiere to see all clases, functions and variables before using them. So it will use the directive on top on the file to bring the code of the required class.

// This indicates the compiler that all the definitions
#include "SpaceShip.h" 
// for the SpaceShip can be found in SpaceShip.h

void myFunction()
{
	SpaceShip mySpaceShip;
	mySpaceShip.shot();
	
	doSomething(); // ERROR This function is being called without being declare first

}

void doSomething()
{
	//Definitions
}

Compilation process

C++ does not have virtual machine (like JAVA), and needs to compile the code before running it (unlike Javascript). The compilation achieves faster execution.

1. Pre-processos runs -> Source(.cpp) and header(.h) files
|		|─ Looks at directives to include (copies and paste) 
|		|		libraries, files, macros, onto the source file.
|		└─ Stops if pre-processor error occurs	
|
2. << Pre-processor OUTPUT
3. Compiler runs the Pre-processor's output
|		└─ Automatically produces a.out for smaller programs
|		└─ Stops if compilation error occurs	
|
4. << OUTPUT: Object files(.o)
5. Linker: Links objects(.o) files together
|	  └─ Stops if compilation error occurs	
|
6. << OUTPUT: binary executable //Runs by the CPU

Pre-processor directives

Allows devs to include C++ libraries.

#include <iostream>

Commands to compile and run

Use g++ main.cpp to compile. The flag -o specifies the name of the .out file.

g++ -std=c++20 main.cpp -o HelloWorld

g++ *.cpp -o myProgram #Will re-compile ALL

#One can separete the compilation process by steps

g++ -E myProgram.cpp > myProgram.s #Creates the compiler file after the pre-processing
g++ -c myProgram.cpp #Compiles to an object .o file
g++ -o myProgram main.o #Links all the objec files together

g++ -std=c++20 main.cpp -o myProgram && ./myProgram

One can re-compile only specific files that have changed. Linking is faster than compiling. This process can be automated using CMake.

*Troubleshooting, When errors occur, read the top of the error stack.

Pass as Value, Reference and Pointers

C++ is pass by value. Which mean, every time we assign a value, or pass a value into a function, we are copying by default. In other languages, like Javascript, it will be pass a reference.

Primitive types

Type	Bytes	Range
char	1
short	2
long	4
int	*(4)	-/+ 32,768
float	4	7 digits
double	8	15 digits
long double	10	19 digits
bool	1	0,1

Operators

pre-increment/decrement ++a --a

post-increment/decrement a++ a--

AND a & b

OR a | b

NOT ~a

References

Dave Churchill (2023) COMP4300 - Game Programming - Lecture 02 - Intro to C++ (1/2) https://youtu.be/rq0oMlWZhdI