Spawn objects within a certain path/countour/object

Unity Engine
1

Hi everyone,

I have a script that creates a grid of squares after being given a width and height and how many rows and columns I want for it. Works great to make rectangular grids, but I want to be able to fill an area with an arbitrary shape determined, ideally, by a surrounding object.

My code works well if I instantiate the objects inside a rectangular tube, but if the tube was , for example, circular, I have no idea how this would work.

This is the code I have at the moment:

    public float areaWidth;
    public float areaHeight;
    public int numberOfBlocksX;
    public int numberOfBlocksY;
    public float factor;

    private Vector3 blockScale;
    private GameObject tempBlock;
 
    void Start () {
        int i=0;
        int j=0;
        
        //Time to create all the blocks we need.
        while (i<(numberOfBlocksX*numberOfBlocksY)) {
            GameObject block = Instantiate (blockType) as GameObject;
            block.name = "block"+i;
            block.transform.localScale = blockScale*factor; 
            i++;
        }
    
        //Now let's position those blocks on a grid, row by row
        for (i=0; i<numberOfBlocksY; i++) {
            for (j=0; j<numberOfBlocksX; j++){
                tempBlock=GameObject.Find("block"+((j*numberOfBlocksY)+i));//This is how to traverse my self made "matrix".
                Vector3 tempPos;
                tempPos.x=(blockScale.x/2)+(blockScale.x*j)-(areaWidth/2);
                tempPos.y=(blockScale.y/2)+(blockScale.y*i)-(areaHeight/2);
                tempPos.z=0.0f;
                tempBlock.transform.position = tempPos;
            }
        }
    
    }

I believe I would have to do quite the rewrite to this to make it approximate other shapes, as this structure is very much a rectangular matrix however way you look at it, so any help appreciated.

I also realize I am kind of making my own matrix structure, perhaps there’s an easier way to make this, but I just couldn’t figure out how to make a matrix in C# in Unity in the way I wanted, because my idea was to have a fixed NxN matrix which I would use as a template on how to instantiate the rectangles (using 0s where none and 1s where an object goes), I just had no idea how to approach that or if it was a better solution. I would still not know how to detect the surrounding shape to approximate to.

Thanks in advance for any info!

2

I have developed something similar in Interactive Terrain asset to generate automatically colliders based on any shape. It is using disc-poisson algorithm.

https://www.assetstore.unity3d.com/en/#!/content/49448

Source code is provided in this asset.

–
Game Rules
Unified Visual Scripting Asset with rules engine

3

That’s cool, thanks for sharing.
I’d like to see some free source though, or rather, talk about it here, so I can learn instead. Not looking for a premade solution.
As much as you are probably aware and used to the algorithm you mention, I never heard of it.
Looked it up and found an article here:
http://gregschlom.com/devlog/2014/06/29/Poisson-disc-sampling-Unity.html
It includes an implementation of said algorithm.

Seems to me this would not be suited to what I want to do though, and more suited to generating random but orderly-looking patterns. I am looking to create precise shapes (hence my example of a matrix filled with 1s and 0s to create a shape) in a very non-random grid shaped after a surrounding object’s mesh.

4

Anyone has any idea how to do this?

5

My idea would be, make a collider. Let’s say, a sphere collider.
For each row, cast one raycast from behind and one from the front. After that, fill all lines between this two points with the blocks. I hope i understood your problem correctly.

6

Hmm, yeah, ray casting, is what I was thinking next, but I haven’t learned how to use them properly yet, so I have no idea how I would apply it to this problem.
Will be good to keep it in mind though, thanks for your input!