• Advertisement
Sign in to follow this  

Unity 2D or 3D physics for a top-down 2D ARPG in Unity?

This topic is 1234 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

Hi,

 

I'm currently setuping my project in Unity. It will be a 2D action RPG.

Though all of the visual will be 2D sprites, I'm concerned that I want to implement features such as jumping over certain obstacles, have some bridges pass over the floor at different heights, and it currently feels like using 3D physics behind the scenes would be much simpler, despite the game being entirely 2D from a visual standpoint.

 

Anyone here tried doing anything a top-down game in Unity? What did you use and why?

Share this post


Link to post
Share on other sites
Advertisement

You can use 2D graphics to emulate 3D objects, but it's really not going to work out for you if you're trying to use 2D physics to emulate 3D physics.  Sounds like you already know the answer to your question.

 

That, and unless you're going crazy with the number of objects that interact with one another, the performance gap between 2D physics simulation and 3D physics simulation isn't big enough to justify shooting yourself in the foot over.

Share this post


Link to post
Share on other sites

So, you assessment is that, regardless of the actual visual output (2d in this case), dropping the Z axis is not a sufficient performance-gainer to justify limiting myself.

That being said, it does come with an added complexity that I need to handle to process collisions.

 

I just feel choosing 3d for a 2d game feels like refusing to use a set of tools optimized for most of what I'm trying to do save for a few things, so I end up handling everything in a 'custom' way because of the few situations that would benefit from that support...

Share this post


Link to post
Share on other sites

I'm by no means an expert in Unity so I'd like to recommend a little sodium chloride with this reply, but in my experience using 3D graphics for a top-down or side-scrolling (parallax) 2D game is unlikely to affect performance much. In fact, the effect would probably be an improvement. Here's my reasoning:

 

In any robust game engine or environment, graphics are usually mixed along alpha channels (etc.) during game play -- characters & obstacles layered on a separate background, etc. In 3D, this is complicated with the addition of a Z axis which requires additional depth management including clipping, occlusion, and so on.

 

At the same time, any 3D engine worth a spit will be efficient, meaning it will not waste too many cycles trying to figure out things like clipping when the graphics blocks are basically just flat planes perpendicular to the Z axis. In effect, the game is simply shifting around postcards on which you probably don't want to apply lighting effects, meaning much of the complexity of a full 3D environment is reduced.

 

Additionally, 3D engines tend to boast their polygon rendering abilities so you know roughly what kind of performance you're likely to get. And beyond this, 3D engines often make direct use of graphics hardware which can greatly increase both rendering speed and free up the main processor for other functions (handling A.I., collision detection, etc.) 2D engines usually use the main computer/device processor so they can boast greater compatibility, but at the cost of raw power and speed.

 

In Adobe Flash, for example, we have had robust 2D graphics since pretty much the inception. Many optimizations have been made to the software to make it efficient, and it was pretty darned good until Adobe introduced direct GPU support. As a result, frameworks like Starling popped up that boasted the same capabilities as Flash 2D but with the ability to handle a lot more while simultaneously freeing up the CPU. In other words, Starling is a 2D game engine that uses Flash's newer 3D capabilities, analogous to your question. The answer that Starling provides is quite clear: 2D games can realize significant performance enhancements (plus easier code/effects), by using a 3D engine.

 

Back to Unity, I'm fairly certain that the same GPU acceleration is used which would lead me to believe that you would be better off using the full 3D engine to create a 2D game; the performance improvements alone would be worth it. Also, as you mentioned, 3D engines tend to have a lot of functionality pre-built -- physics, collisions, etc. It's nice to know how these work but if you're more concerned with actually building the game, these topics are probably best saved until later.

 

My two cents smile.png

Edited by Patrick B

Share this post


Link to post
Share on other sites

Thanks, but I think my concern doesn't really lie with performance, but rather, ease of use for game logic (handling collisions, etc.).

Assuming I want to have stuff like jumping and overpass bridges/mezzanines, I felt 3D makes it easier to handle, but that would also mean I need to attach 3d collision boxes to actual 2d sprites, which feels a bit counter-intuitive?

Share this post


Link to post
Share on other sites

Try both, there's no wrong one.

 

Really, you're using Unity, it's really easy to try both approaches, you don't even need to remove one to create the other, just disable the 2D or 3D collision components and enable the others, you don't even have to replace code since each 3D collision callbacks has a different name in 2D (OnTriggerEnter and OnTriggerEnter2D, etc). Setup some test scenes with the things you have in mind (jumping over enemies, different heights, etc) and try them if you're not sure.

 

Anyway, for a 2D game I think I would go with 2D collision detection and use the z axis values or some flags to check if the collision should be considered or not, it doesn't look like too extra work and maybe you can prevent weird bugs related to the 3D collision volume that you wouldn't notice in a 2D view. Also, 3D and 2D physics use a different axis for gravity and that could lead to more weird bugs, so that's another reason I'll do it in 2D.

Share this post


Link to post
Share on other sites


ust disable the 2D or 3D collision components

 

Wouldn't my code still run actual vector2D vs Vector3D ?

I'd still need to change the code to switch between the two, no?

 


Anyway, for a 2D game I think I would go with 2D collision detection and use the z axis values or some flags to check if the collision should be considered or not, it doesn't look like too extra work and maybe you can prevent weird bugs related to the 3D collision volume that you wouldn't notice in a 2D view. Also, 3D and 2D physics use a different axis for gravity and that could lead to more weird bugs, so that's another reason I'll do it in 2D.

Makes sense. I was going to do something along these lines in 2D.

 

Thanks.

Share this post


Link to post
Share on other sites

 


ust disable the 2D or 3D collision components

 

Wouldn't my code still run actual vector2D vs Vector3D ?

I'd still need to change the code to switch between the two, no?

Even in 2D, Unity puts everything in a 3D world, so the game objects would have a position with x, y and z values in both cases (Vector3). You'll always see the 3 components in the editor, and if you change your scene view from 2D to 3D you'll see that the z value is being used.

 

Also, you can have one script that handles 2D collision and another that handles 3D collision so you don't need to change code, just enable/disable those too depending on what you're testing, and then call methods of another script that does the logic you want for a collision.

Share this post


Link to post
Share on other sites


Also, you can have one script that handles 2D collision and another that handles 3D collision so you don't need to change code, just enable/disable those too depending on what you're testing, and then call methods of another script that does the logic you want for a collision.

 

Ok yes, that's what I meant. 

 

Thanks.

Share this post


Link to post
Share on other sites

Use 3d physics. 2d physics in Unity are more catered towards sidescrollers, for example gravity is either x or y axis so you would have to use kinematic rigidbodies and handle jumping yourself. Methods like transform.LookAt() don't work out of the box. etc. I made couple of top down prototypes a while ago, in the end I switched to 3d physics. The performance gain with 2d was so marginal it was not worth it even on mobile.

 

Also, there are things not available with 2d physics, like particle collision detection.

 

 

 

Thanks, but I think my concern doesn't really lie with performance, but rather, ease of use for game logic (handling collisions, etc.).

Assuming I want to have stuff like jumping and overpass bridges/mezzanines, I felt 3D makes it easier to handle, but that would also mean I need to attach 3d collision boxes to actual 2d sprites, which feels a bit counter-intuitive?

 

Forgot to mention that 3d physics with sprites felt a lot more comfortable to me, as you can give volume to the colliders.

Edited by dissid

Share this post


Link to post
Share on other sites
Sign in to follow this  

  • Advertisement
  • Advertisement
  • Popular Now

  • Advertisement
  • Similar Content

    • By eldwin11929
      We're looking for programmers for our project.
      Our project is being made in Unity
      Requirements:
      -Skills in Unity
      -C#
      -Javascript
      -Node.js
      We're looking for programmers who can perform a variety of functions on our project.
      Project is a top-down hack-and-slash pvp dungeon-crawler like game. Game is entirely multiplayer based, using randomized dungeons, and a unique combat system with emphasis on gameplay.
      We have a GDD to work off of, and a Lead Programmer you would work under.
      Assignments may include:
      -Creating new scripts of varying degrees specific to the project (mostly server-side, but sometimes client-side)
      -Assembling already created monsters/characters with existing or non-existing code.
      -Creating VFX
      -Assembling already created environment models
      If interested, please contact: eldwin11929@yahoo.com
      This project is unpaid, but with royalties.
       
      ---
      Additional Project Info:
      Summary:
      Bassetune Reapers is a Player-verus-Player, competitive dungeon crawler. This basically takes on aspects of dungeon crawling, but with a more aggressive setting. Players will have the option to play as the "dungeon-crawlers" (called the 'Knights', or "Knight Class", in-game) or as the "dungeon" itself (literally called the 'Bosses', or "Boss Class", in-game). What this means is that players can choose to play as the people invading the dungeon, or as the dungeon-holders themselves.
      Key Features:
      -Intense, fast-paced combat
      -Multiple skills, weapons, and ways to play the game
      -Tons of different Bosses, Minibosses, creatures and traps to utilize throughout the dungeon
      -Multiple unique environments
      -Interesting, detailed lore behind both the game and world
      -Intricate RPG system
      -Ladder and ranking system
      -Lots of customization for both classes s of customization for both classes
    • By RoKabium Games
      Custom coffee mugs have arrived... More caffeine!
      Have a great weekend everyone! 
      #gamedev #indiedev #sama #caffeine
    • By Atwo Studios
       
      Hey guys,

      Anthony here from Atwo Studios bringing you some new updates for the new year!
      In this video I go over our game ROY, the new games and some general updates to the company!

      If you have not checked out ROY feel free to give it a try! Many people have said they enjoyed the game thus far!
      ROY: https://goo.gl/o6JJ5P
       
    • By Affgoo
      https://play.google.com/store/apps/details?id=com.NE.Alien
      still a lot of work to do, but its pretty stable  please let me know what you think <3
      Atlas Sentry is a game of destroy everything. Using your turret, simply swivel and shoot your way to victory, upgrading your weapons to unleash destruction on the variety of spaceships. The bigger your combo’s the more score you get! Earn silver as you play and then purchase new weapons and abilities to better deal with your enemy. Different enemies use different tactics and weapons, work out your own priorities in their destruction order. 

      Features: 
      **2 different game modes 
      **A level select mode with 20 difficult levels including a final boss, can you defeat it? **Arcade mode of endless destruction, how long will you last? 
      **High scores to compete against others, see who can take the top spot. 
       
    • By Chamferbox
      Chamferbox, a mini game asset store has just opened with some nice game assets, 
      Here you can find a free greek statue asset 

      Also check their dragon, zombie dragon and scorpion monster out:



      They're running the Grand Opening Sale, it's 30% off for all items, but for gamedev member, you can use this coupon code:
      GRANDOPEN
      to get 50% off prices What are you waiting for, go to
      http://chamferbox.com
      and get those models now!

      View full story
  • Advertisement