What is the difference between marching cube and octree?

Question

Is octree a special case of marching cube ?? I mean does octree use same triangulated cubes of marching cube. I know that octree is a 3d form of quadtree. I just want to know whether I am in correct direction or not. After the tree have been formed, how does octree does the step for formation of triangles ( for creating the surface) is it same as that of marching cube?

Answer 1

it is a completely different theory. Octree is a cubic subdivision method for 3d space, to find distributions of things in space, to efficiently process large spaces and narrow it down to the areas where there is something to find.

Marching cubes is a system for generating mesh and doesn't use any progressive subdivision like octree.

But a good marching cube system would use octree to find the areas that need to be processed and throw out things without mesh in it. https://www.youtube.com/watch?v=gNZtx3ijjpo

Answer 2

Marching cubes is a method for triangulating an iso-surface of a function, by subdividing into equally sized small cubes and triangulating each cube in a way that preserves continuity.

An octree base iso-surface method instead chops into non-uniformly sized cubes. This can generate a lower number of triangles than a marching cube algorithm for equivalent "visual quality". However the extra cost is that many special cases need to be handled in triangulating the surfaces in each cube to avoid holes. Also you must determine a metric for when each cube is "small enough" (compared to the changes in value in the cube and the visual importance of the cube etc.). Often to help reduce the number of special cases neighbouring cubes are limited to differ by at most one octree level - meaning that simple refinement purely on the metric is not possible.

So in summary: marching cubes is a fast iso-surface triangulation method. Octree methods are more complicated but can give better results. They are not the same, and octree is not a special case of marching cubes.