在2D游戏中跳跃并站立在物体上

Question

Im making small 2D game and i would like how should, theoretically work jumping and standing on objects.
For jumping should there be some kind of gravity?Should i use collision detection?
Good example of what i want to undestand is jumping in Mario.

Answer 1

I think for jumping it would be best to create some simple model which use "game time". I would personally create some physical model based on gravity, but you can go for whatever you want.

If you want your character to "stand" on object, you will have to create some collision detection. Good start is to approximate object by one or more circles (or lines) compute collision of them and in case the approximation collides determine the final state by some more precise method.

Answer 2

In terms of should there be gravity and collision detection - personally for such a thing I'd say yes and yes! It doesn't have to be complicated but once you have those things in place the pseudocode for the "main loop" becomes relatively simple:

if not colliding with object underneath, apply gravity
if user presses jump key and not colliding with surface //i.e. if we're in the air already, don't jump again
    apply upward velocity

That is of course oversimplified and there are other corner cases to deal with (like making sure when you're coming down after jumping, you don't end up embedded or potentially going through the floor.

You might want to take a look at Greenfoot which handles a lot of things like all the Java2d stuff, collision detection etc. for you. Even if you don't stick with it it'd be a good platform for building a prototype or playing around with the ideas talked about.

Answer 3

Standing on objects implies collision detection, you can approximate the characters and the environment objects with primitive shapes (rectangles, circles etc.). To check if to shapes are colliding, check axis one by one (X and Y axis in your case). Here is an explanation of the "separating axis theorem" (Section 1).