Question

I have an array that represents a grid

For the sake of this example we will start the array at 1 rather that 0 because I realized after doing the picture, and can’t be bothered to edit it

In this example blue would have an index of 5, green an index of 23 and red 38

Each color represents an object and the array index represents where the object is. I have implemented very simple gravity, whereby if the grid underneath is empty x + (WIDTH * (y + 1)) then the grid below is occupied by this object, and the grid that the object was in becomes empty.

This all works well in its current form, but what I want to do is make it so that red is the gravity point, so that in this example, blue will move to array index 16 and then 27.

This is not too bad, but how would the object be able to work out dynamically where to move, as in the example of the green grid? How can I get it to move to the correct index?

Also, what would be the best way to iterate through the array to ‘find’ the location of red? I should also note that red won’t always be at 38

Any questions please ask, also thank you for your help.

Answer 1

This sounds very similar to line rasterization. Just imagine the grid to be a grid of pixels. Now when you draw a line from the green point to the red point, the pixels/cells that the line will pass are the cells that the green point should travel along, which should indeed be the shortest path from the green point to the red point along the discrete grid cells. You then just stop once you encounter a non-empty grid cell.

Look for Bresenham’s algorithm as THE school book algorithm for line rasterization.

And for searching the red point, just iterate over the array linearly until you have it and then keep track of its grid position, like William already suggested in his answer.