Checking if an object is fully inside another object

[Makkeonmies]

I have a room where its all covered with invisible blocks, along 64x64 grids.
If the player object presses a certain key, a block object on top of which it currently is should activate. However the player sometimes overlaps two of these at a time. I cant make the collision mask of the blocks much smaller either. How can i make the player character only activate a block object that it is fully inside of, not so that it activates all blocks the player object even partially collides with?

 

[Annoyed Grunt]

you can use

rectangle_in_rectangle(sx1, sy1, sx2, sy2, dx1, dy1, dx2, dy2);

to determine if two rectangles are fully intersecting each other.

 

[IndianaBones]

Use something like collision_point() to determine which block the player is above, then use rectangle_in_rectangle() function to work out if the player is fully inside that block.

 

[Makkeonmies]

thanks for replies. will try these out when getting back to my project.

 

[Makkeonmies]

how will i mark the player object's coordinates in rectangle_in_rectangle? Does it matter if the player object is not rectangular, should i use some other function?
The player objects sprite's size is 42 x 42, in case it matters. Should I mark that as the 'destination rectangle to check against' ?
Or does it go smth like:

rectangle_in_rectangle(sx1, sy1, sx2, sy2, playerobj.dx1, playerobj.dy1, playerobj.dx2, playerobj.dy2);

Never used this function before, so sorry for all the questions

 

[woods]

would instance_nearest be of use here?

 

[Bentley]

I have a room where its all covered with invisible blocks, along 64x64 grids.
If the player object presses a certain key, a block object on top of which it currently is should activate. However the player sometimes overlaps two of these at a time. I cant make the collision mask of the blocks much smaller either. How can i make the player character only activate a block object that it is fully inside of, not so that it activates all blocks the player object even partially collides with?

To check if the player is completely inside a block:

var block, x1, y1, x2, y2, x3, y3, x4, y4;

block = instance_place(x, y, o_block);
if (instance_exists(block))
{
    x1 = bbox_left;
    y1 = bbox_top;
    x2 = bbox_right;
    y2 = bbox_bottom;
    x3 = block.bbox_left;
    y3 = block.bbox_top;
    x4 = block.bbox_right;
    y4 = block.bbox_bottom;
    if (rectangle_in_rectangle(x1, y1, x2, y2, x3, y3, x4, y4) == 1) // Only true if you're completely inside a block
    {
        // Do something
    }
}

Edit: ignore what I wrote below if you just want to check if the player is entirely inside. Also, @IndianaBones post about using collision_point is a better approach than mine.

Assuming you want something to happen when you're overlapping, change the check to be > 0.
The problem will be when you are overlapping two rectangles. The instance_place could return the ID of the lesser of the two rectangles you're overlapping.

Off the top of my head, a collision list and then store the nearest rectangle. Surely there's a better way but that's probably how I would do it.

 

[IndianaBones]

Off the top of my head, a collision list and then store the nearest rectangle. But there's probably a more efficient that someone smart than me can tell you about.

That's a good solution, should work in all cases.

I suggest, if the sprite x and y offset for your player is centered, replacing instance_place() with collision_point() and using the players x and y position should do the trick.

If the player's x and y are outside of a block, then the rest of the player sprite is definitely not going to be within the block entirely.

You can always test it to confirm what method works best.

 

[Makkeonmies]

To check if the player is completely inside a block:

var block, x1, y1, x2, y2, x3, y3, x4, y4;

block = instance_place(x, y, o_block);
if (instance_exists(block))
{
    x1 = bbox_left;
    y1 = bbox_top;
    x2 = bbox_right;
    y2 = bbox_bottom;
    x3 = block.bbox_left;
    y3 = block.bbox_top;
    x4 = block.bbox_right;
    y4 = block.bbox_bottom;
    if (rectangle_in_rectangle(x1, y1, x2, y2, x3, y3, x4, y4) == 1) // Only true if you're completely inside a block
    {
        // Do something
    }
}

The problem will be when:
1. You are overlapping one rectangle
2. You are overlapping two rectangles
Assuming you want something to happen when you're overlapping, change the check to be > 0.

The problem about colliding with 2 rectangles remains. The instance_place could return the ID of the lesser of the two rectangles you're overlapping.

Off the top of my head, a collision list and then store the nearest rectangle. Surely there's a better way but that's probably how I would do it.

this actually works! no overlapping issues anymore, the player object can only activate a block now when completely inside one, and nothing happens when player overlaps more than 1 blocks.
Thanks to all of you guys who posted here!
especially @Bentley !