java grid collsions detection

Newbie & Debugging Questions
#1

hey guys i have been trying to browse youtube and JGO for any tutorials on grid based collision detection but i can’t seem to find any also i need to be able to build maps out of blocks so i need the grid for that aswell :stuck_out_tongue: any help appreciated as its my first game ever and im struggling a bit :stuck_out_tongue:

#2

When you say grid collision, is each entity contained only inside a grid cells?
If you store all your entities in an array [ ][ ], then you can check neighboring cells, with a range of entity’s x-1 to entity’s x+1 and entity’s y-1 to entity’s y+1. Or just check the cell the entity is moving into.
For storing you can use Entity[ x ][ y ] (or Entity[ x ][ y ][ z ] ).

Aazimon

#3

i really don’t know lol, never worked with a grid before but i am going to check for collisions with objects in the cell yes… but i havfe no idea of how to create “the grid” and so on xD

#4

Don’t worry about problems too much before you’ve even started.

And the way Aazimon said will work. Can’t/shouldn’t have 2 different things on the same tile/cell.

#5

yea i see :stuck_out_tongue: but does anyone know of any tutorials or just something that explains the way to make it ?

#6

You’re probably using java 2D, but oh well…
http://cokeandcode.com/index.html?page=tutorials/tilemap1
made by kevglass (duke on this forum)
it’s for Slick, I think, but explains the idea pretty well. There’s also an A* pathfinding tutorial there.

#7

yea but it still does not explain how to make the grid, it just repeats everything i have read elsewhere :stuck_out_tongue: and i understand all of that i just don’t know how to create the grid

#8

Well, creating the grid is just taking an array[][]. I really don’t know how you are attempting to make the grid. Are you using images, Java2D, OpenGL, Slick?

Regardless, if you want to make a simple 10x10 grid and your “block” objects are 16x16. Here is a snippet that might help (assuming Java2D).



//You can use an array to store images
Image[][] blockarray = new Image[10][10];

public void render(Graphics g)
{
     g.setColor(Color.BLUE);
     for(int i = 0; i < 10; i++){
           for(int j = 0; j < 10; j++){
                 g.fillRect(16*i, 16*j, i, j);//Normal grid with Blue rectangles
                 g.drawImage(blockarray[i][j], i*16, j*16, <Component>);//Image grid
           }
     }
}
#9

Are you wanting to make the Grid lines?
This piece of code will draw grid lines for you.


g2d.setColor(Color.BLACK);
// make the lines dotted lines.
g2d.setStroke(new BasicStroke(1.0f, BasicStroke.CAP_BUTT, BasicStroke.JOIN_MITER, 1.0f, new float[]{3.0f, 3.0f}, 0.0f));
for (int x = 0; x< totalWidth; x+= gridWidth) {
  g2d.drawLine(x, 0,x, totalHeight);
}
for (int y = 0; y< totalHeight; y+= gridHeight) {
   g2d.drawLine(0,y,totalWidth,y);
}