Differences between Source Port and Emulation?

[SweetShark]

So I wanted to ask this question for a long time.
So recently I played a game which have the name "Nocturne in Yellow".
I thought at first it was a pure Mod for DOOM and for sure it would used DOSBox to operate the game.
I was wrong of course because I checked later the files and I saw it is a Source Port base the GZDoom, names GLOOME.
So at this point I am really confused.
Any kind of detailed answer to tell me why is so different?

 

[Supernova1138]

A Source Port is the game modified to run natively on modern OSes and hardware, along with adding additional graphical features, and in the case of Doom allowing vertical aiming. Emulation would be something like DOSBox which creates a virtual DOS PC that runs the original 1993 game in a DOS environment with all the limitations of the original game still intact. A lot of Doom mods these days do require a source port as they tend to do things that exceed the limitations of the original Doom engine.

 

[SweetShark]

A Source Port is the game modified to run natively on modern OSes and hardware, along with adding additional graphical features, and in the case of Doom allowing vertical aiming. Emulation would be something like DOSBox which creates a virtual DOS PC that runs the original 1993 game in a DOS environment with all the limitations of the original game still intact. A lot of Doom mods these days do require a source port as they tend to do things that exceed the limitations of the original Doom engine.

So I guess the game I mentioned, Nocturne in Yellow, isn't really a DOS game even though it use the source of the original DOOM?

 

[CaitSeith]

A Source Port is the game modified to run natively on modern OSes and hardware, along with adding additional graphical features, and in the case of Doom allowing vertical aiming. Emulation would be something like DOSBox which creates a virtual DOS PC that runs the original 1993 game in a DOS environment with all the limitations of the original game still intact. A lot of Doom mods these days do require a source port as they tend to do things that exceed the limitations of the original Doom engine.

So I guess the game I mentioned, Nocturne in Yellow, isn't really a DOS game even though it use the source of the original DOOM?

In the 90s, ID Software made the DOOM Engine open-source. People used it as a blueprint to code from zero an engine that worked on a different system. But the engine doesn't include the game maps (except the first chapter) for copyright reasons. Emulation is more complicated because is pretty much reverse-engineering.

 

[Avnger]

One way to think of it is that an emulating a game means the program makes all of its original system and function calls which a second program then interprets into whatever modern system it is running on.

Source porting a game requires actually re-programming parts of the game to make it utilize modern day system calls and functions on its own.

Emulation: 3rd party interprets game calls for a modern system
Source port: game calls changed to those for a modern system