How easy would it be to make game similar to DOOM?

I want to make a doom like game (but with zombies and survival elements) what will i need to learn and what software other than unity will i need.
how do i make the 2d sprites?

 

photoshop, ms paint?

 

Consider buying a shooter framework like UFPS or Realistic FPS Prefab. Then you just need to add your artwork and you're basically done except for saved games. You can buy another package for saved games and get it working with your shooter framework.

id hand-drew many of the monsters in DOOM, and photographed the rest from clay sculptures, like claymation. For the weapons, they went to Toys'R'Us and photographed toy weapons. Shooter frameworks usually come with a variety of weapon models.

For audio, you can record sound effects yourself or get some free ones from http://freesound.org and music from http://incompetech.com/music/royalty-free or APM on the Unity Asset Store.

 

inkscape is a great free vector drawing software, and then there are programs like gimp that i belive are raster programs for image editing and painting.

 

From a technical stand point, FPS are easy to build. Create terrain, add a character controller, add basic ray casting for shooting, add some enemies with basic AI and you are done.

You can do a lot more with a shooter, but that's about all doom had.

 

Thank you so much for the help its much appreciated.

 

The only thing I'd add is: be careful not to dissect very old games like DOOM too much in making a First Person Shooter, as they were forced to do many work-arounds due to technology limitations. Relying on Sprites for a 3D style game is one example. Most likely, you will want to use animated 3D models for your monsters. For this, you can rely on the Asset Store for material.

 

the reason i wanna make a game with 2d sprites in a 3d world in because i love the look and feel of those kinda games.

 

http://forum.unity3d.com/threads/doom-2d-3d-sprite-functions.288133/
http://forum.unity3d.com/threads/wi...rite-a-directional-billboarded-sprite.224710/
http://answers.unity3d.com/questions/404947/8-directional-sprite-in-3d-world-how-to-retrieve-d.html

 

Thanks for posting those links it helps alot