Collision between rectangles

Processing Coding Questions
1

I am trying to make collision between rectangles in my game. The player can move with W, A, S, D and there are ‘blocks’ that the player is supposed to collide with. I’m able to make it so the player can collide normally along 1 axis, but whenever I combine the x and y axis it creates strange behaviour. I’ve tried making it so it checks which axis the player is closer to the center of the block on, but it only makes it worse.

if (pos.x + WIDTH / 2f > block.pos.x - block.width / 2f && pos.x - WIDTH / 2f < block.pos.x + block.width / 2f
                    && pos.y + HEIGHT / 2f > block.pos.y - block.width / 2f && pos.y - HEIGHT / 2f < block.pos.y + block.height / 2f)
            {
                float dx = Application.dist(pos.x, 0, block.pos.x, 0);
                float dy = Application.dist(0, pos.y, 0, block.pos.y);

                if (dx < dy)
                {
                    // left
                    if (pos.x + WIDTH / 2f > block.pos.x - block.width / 2f && pos.x < block.pos.x)
                    {
                        pos.x = block.pos.x - block.width / 2f - WIDTH / 2f;
                    }
                }
                else
                {
                    // top
                    if (pos.y + HEIGHT / 2f > block.pos.y - block.height / 2f && pos.y < block.pos.y)
                    {
                        pos.y = block.pos.y - block.height / 2f - HEIGHT / 2f;
                    }
                }

                if (dx < dy)
                {
                    // right
                    if (pos.x - WIDTH / 2f < block.pos.x + block.width / 2f && pos.x > block.pos.x)
                    {
                        pos.x = block.pos.x + block.width / 2f + WIDTH / 2f;
                    }

                    // bottom
                    if (pos.y - HEIGHT / 2f > block.pos.y + block.height / 2f && pos.y < block.pos.y)
                    {
                        pos.y = block.pos.y + block.height / 2f + HEIGHT / 2f;
                    }
                }
            }

I also know why it doesn’t work, though I don’t have a clue on how to fix it.

2

Hi

1 Like
3

You don’t show, how you draw your blocks.
If you didn’t change rectMode the position of the block is in the upper left corner.

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4

Oh sorry about that. I use rectmode center.

5

Solution:

for (Block block : blocks)
        {
            float dx = Application.dist(pos.x, 0, block.pos.x, 0);
            float dy = Application.dist(0, pos.y, 0, block.pos.y);

            if (dx > dy)
            {
                // left
                if (pos.x + WIDTH / 2f > block.pos.x - block.width / 2f && pos.x < block.pos.x)
                {
                    pos.x = block.pos.x - block.width / 2f - WIDTH / 2f;
                }

                // right
                if (pos.x - WIDTH / 2f < block.pos.x + block.width / 2f && pos.x > block.pos.x)
                {
                    pos.x = block.pos.x + block.width / 2f + WIDTH / 2f;
                }
            }
            else
            {
                if (pos.y + HEIGHT / 2f > block.pos.y - block.height / 2f && pos.y < block.pos.y)
                {
                    pos.y = block.pos.y - block.height / 2f - HEIGHT / 2f;
                }

                if (pos.y - HEIGHT / 2f < block.pos.y + block.height / 2f && pos.y > block.pos.y)
                {
                    pos.y = block.pos.y + block.height / 2f + HEIGHT / 2f;
                }
            }
        }

(Sorry about the formatting)

I don’t know if this is a good way, but it achieves exactly what I wanted, so.

1 Like