Digging a River

When we pulled up vertices[50], we pulled up the vertex at the top-middle of the plane. When we added 100, 10*100, and 50*100 to 50, we pulled up vertices in a straight line.

 var​ faces = 99;
 var​ shape = ​new​ THREE.PlaneGeometry(10, 20, faces, faces);
 shape.vertices[50].z = 5;
 shape.vertices[50 + 100].z = 5;
 shape.vertices[50 + 10*100].z = 5;
 shape.vertices[50 + 50*100].z = 5;

There are 99 rectangles across the top of the plane. That means there are 100 vertices—the 99 top-left corners plus the top-right corner on the end. So every time we move 100, we move to the next row.

We can make use of this in a for loop. Instead of starting the loop at 0, we can start at 50. And, instead of increasing by 1 each time through ...

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