Creating a Grid / 2D Mesh.

Programming Questions

eightohni..

in Programming Questions • 3 years ago

Hi all,

what I first believed to be a more or less easy task turned out to tie knots in my brain.

Basically, I want to create an orthogonal grid, where it's possible to manipulate the position of every single vertice in a 2D space. So when one vertice is moved, all the lines connecting that vertice to it's neighbours move accordingly.

I believe such a thing is called a mesh?

I know that there is a mesh–library out there somewhere, but I'd like to try and build the mesh from ground up.

I know how to generate the original positions of the vertices on a grid.

But I have no clue as how to best tell every vertice who his neighbours are and to remain connected to them all the time. Because not all vertices have the same amount of connections:

- in the corners they have two

- on the edges they have three

- everywhere else they have four

And how do I prevent two vertices to connect themselves twice? (Once in ever direction)

Finally, the whole construct should not be to intense to compute, since I'd want it to be dynamic.

Is such a task feasible for a beginner/intermediate user?

Or are we talking about a rather complex problem here?

If anyone has some pointers as to how I should approach this task I'd be really thankful.

Thanks!

cheers,

Greg

Replies(4)

antiplast..

Re: Creating a Grid / 2D Mesh.

3 years ago

Use objects.

The vertices are PVector objects, right?

The segments are custom objects (that you'll define) containing two references to vertices :

class Segment {
PVector start, end;
}

So you'll need an array (or arraylist) of vertices, and an array (or arraylist) of segments :

PVector[] vertices;
Segment[] segments;

ArrayList vertices; // an ArrayList of PVector objects
ArrayList segments; // an ArrayList of Segment objects

Then you'll just have to create your mesh once. I would suggest you first create the vertices (one loop) then create the segments (second loop).

eightohni..

Re: Creating a Grid / 2D Mesh.

3 years ago

Thanks for the pointers.

Unfortunately, I've never been good friends with the PVectors. Seems to be the right time to get to know them better.

What still remains is how to iterate through every vertices and link to all it's neighbours.

I guess first I need to check the position of the vertice (corner, edge or else)

This gives me the number of neighbours.

For every neighbour I use the current vertex loc and the loc from it's neighbour to create a segment and write it to the segment-arraylist.

Now I only have to make sure, that I later don't create a segment, which already has been created from the other direction.

This sound about right?

When I want to transform the mesh, I change the locs of the vertices.

And afterwards I tell every segment in the arraylist to update it's start and endpoint based on it's two assigned vertices.

Should be a fun little project.

antiplast..

Re: Re: Creating a Grid / 2D Mesh.

3 years ago

Since you are creating the grid, you know the position of every vertex. The first one may be at top-left corner, the last one at bottom-right corner. Just iterate and create two segments for each point (except for last col and last row : only 1 segment and last point : already connected).

You will update the vertices, but you won't have to update the segments. Since they contains pointers (references to PVector objects), they'll update themselves. Redrawing them will be enough.

Btw, PVectors are very easy to play with.

eightohni..

Re: Creating a Grid / 2D Mesh.

3 years ago

Awesome, thanks for clearing things up.

This should bring me a long way.

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