java grid collsions detection

[Xenon]

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 any help appreciated as its my first game ever and im struggling a bit

[aazimon]

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

[Xenon]

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

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[Jimmt]

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.

[Xenon]

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

[Jimmt]

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.

[Xenon]

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

[ctomni231]

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).

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//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           }      } }

[aazimon]

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

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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); }