CODEWITHSUNDEEP
language-agnosticcollision-detection
Null Spark
Null Spark

Reputation: 409

How do I detect if an object is on top of another object (like Mario on a brick)

I am building an auto-run platforming game. I have code so that if the character collides with a wall, they are pushed back until they are able to get past the wall. Unfortunately, this means that when the character tries to jump on an object, he just gets pushed backward. How do I discern when a character is on top of an object, from when it is on the side?

My Current Algorithm (c-ish because i like c-ish syntax):

if (wall.Top < (character.Top + character.Height) &&
    wall.Left < (character.Left + character.Width) &&
   (wall.Top + wall.Height) > character.Top &&
   (wall.Left + wall.Width) > character.Left) { #code here# }

Upvotes: 0

Views: 28

Answers (1)

Frank Puffer
Frank Puffer

Reputation: 8215

Four conditions are too much here. Depending on the heights of the character and that of the wall, the 1st and the 2nd condition eliminates cases where actually your character is on the wall.

Assuming that you consider the character to be on top of the wall if its center bottom is on top of the wall, you could do the following:

character.Center = character.Left + character.Width / 2;
if (character.Center > wall.Left &&
    character.Center < wall.Left + wall.Width &&
    character.Top - character.Height > wall.Top) { ... }

Upvotes: 1

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