2D Portal Physics?

Question

Hi all!

I'm trying to replicate this game using Unity (I have Playmaker too, but I don't think it's much of use here):

https://www.cemetech.net/forum/viewtopic.php?t=10751&postdays=0&postorder=asc☆t=0&sid=0febf7805304b3282329ef39cd6f1a63

It's basically a 2D platform game which uses portals, in a similar way to Valve's Portal games, to help you reach a 'gate' in order to go to the next level.

I have tried multiple things on my own without success, and then I've made some research over here and on YouTube, but I'm unable to get what I want.

Things missing from the portal physics that I have already tried:

1- The player sprite must always be facing up, therefore with its rotation 'stuck'.

2- Momentum needs to stay constant when going through a portal. This way, having two horizontal portals, with one being higher than the other, allows the player to keep jumping higher and higher.

3- When a player is halfway through a portal, then it should be also halfway sticking out of the other portal. Therefore, if you enter a vertical portal, then the right part of your body should be missing, and if the other portal is horizontal (facing downwards), then the feet should start appearing. But the player will only drop down when he is completely through the vertical portal. What would be the best way to do this? Should I focus on instantiating gradually a new player, or 'teleporting' part of it at a time?

4- The game you can see through the link I posted above only uses portals vertically or horizontally, and the player keeps horizontal strafing freedom (he can keep going left and right even in the air). I was thinking of adding portal possibilities at 45 degree angles? Would this be possible while maintaining #3, or is it simpler to keep portals at 90 degree increments?

I'm still learning to use Unity, although I've recently finished my first game (it's on the Google Play Store too!)

Could you please give me any tips suggesting which paths I should take to achieve my goals? Or maybe some code to start me off too?

Thanks! :)

Answer 1

I've never made a game that uses this kind of mechanic, but these are my thought.

1) Easy. Just never touch rotation.

2) Just keep track of your movement. Easily done using Rigidbody2D.velocity

3) This is where game trickery comes into play. You have 2 options that you already mentioned.

Break the character apart into small components and transport them through slowly. I honestly think this will be much too difficult to make it worth it.
Instantiate a new character and initialize its velocity to be the same as the 'current character'. I would also probably put a collider on the portal just behind the wall so once the character goes into the portal, then he will be instantiated as coming out of the other portal.

In order to initialize the new character, you will basically create a new object and assign it to the new character. Then call the appropriate function and pass the parameters you need.

4) For the 45 degree portals, instead of having them only interact if if you are coming straight into them. They will be able to handle vertical or horizontal entry.

Once again, I've never done this mechanic. These are just my first thoughts.

2D Portal Physics?

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