now...lets move to my collision checking problem.

Do you check for collision graphically? I mean by checking if two objects overlap the pixel...

I thought if I have a 2d array keeping record all the objects on the grid, while an object moves the array would be updated accordingly and if an object tries to move to a position which already holds an object, it would detect a collision. Wouldn't this type of collision checking work?

It depends -- if you require very precise collision detection, then this would be one option. But, in the situation you describe below...



... this would work. If your movements are all strictly grid-based, then grid-based collision detection like you just described would be all you really need.

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A simple method for collision detection is bounding boxes.

http://content.gpwiki.org/index.php/VB: ... _Detection

Circular collision is fairly easy too, choose the method that suits your game best.

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10 PRINT "Bad Monkey ";
20 GOTO 10

Well I thought I would use two layers of rendering, first the background map and above it a grid. The background map would have only tiles and no objects, then I would make a grid mimic each tiles height and draw object on grid. A static background and a dynamic grid foreground, but so far there are few problems I got stuck on.

First is the height of the grid tiles. I know tileWidth = 2 * tileHeight, but what about elevated tiles?
I thought if height = 1, I would raise the tile by half of tileHeight and so on. And it gives me this.

Zero height....ignore the rock and the green filled tiles is because the mouse was over it.

height = 1 works fine, mouse picking works.

But height = 2 is bad, it completely overlaps the top-most tile.
That's my first problem.

And because of the two layers I always have to clear two overlapping objects, like

It works fine right? But the clearing algorithm also clears translated objects. Suppose that rock is moving to the next x-index. And visually...

This happens! I think I need to work with pixel clearing algorithm, but how? Height = 1 over laps 3 upper tiles at least.
This here is my second problem.

Or you could question my 2 layered concept, and tell how you folks do it?

The easiest way to do this is to use 3D (OpenGL or DirectX) to do the drawing. You can have an 'isometric' game by using an Orthographic_projection, that way you don't have to worry about tiles overlapping. Also tile 'picking' is relatively simple.

I am not sure I fully understand whats happening in the last one, but can't you make it so each layer of tiles (layer == height) would be a different array? Then your objects could track which layer are they on, and render based off that. Also if, lets say, the player walks behind a "mountain" (which are bunch of tile layer higher then the player) then every layer above the player would be rendered sami-transparent (example, alpha 35 or so), that would make everything behind the mountain or house or tree visible to the player. This might require you to rewrite some of the code so I am posting it only as an /Idea/. But if you could explain what is the "clearing algorithm" doing exactly, we might be able to help further with your original code.

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