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Editorial Team
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Asked: 2026-05-30T09:22:17+00:00

I have a simple game that uses a 3D grid representation, something like: Blocks

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I have a simple game that uses a 3D grid representation, something like:

Blocks grid[10][10][10];

The person in the game is represented by a point and a sight vector:

double x,y,z, dx,dy,dz;

I draw the grid with 3 nested for loops:

for(...) for(...) for(...)
   draw(grid[i][j][k]);

The obvious problem with this is when the size of the grid grows within the hundreds, fps drop dramatically. With some intuition, I realized that:

  • Blocks that were hidden by other blocks in the grid don’t need to be rendered
  • Blocks that were not within the person’s vision field also don’t need to be rendered (ie. blocks that were behind the person)

My question is, given a grid[][][], a person’s x,y,z, and a sight vector dx,dy,dz, how could I figure out which blocks need to be rendered and which don’t?

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1 Answer

  1. Editorial Team

    I looked into using JMonkeyEngine, a 3D game engine, a while back and looked at some of the techniques they employ. From what I remember, they use something called culling. They build a tree structure of everything that exists in the ‘world’. The idea then is that you have a subset of this tree that represents the visible objects at any given time. In other words, these are the things that need to be rendered. So, say for example that I have a room with objects in the room. The room is on the tree and the objects in the room are children of the tree. If I am outside of the room, then I prune (remove) this branch of the tree which then means I don’t render it. The reason this works so well is that I don’t have to evaluate EVERY object in the world to see if it should be rendered, but instead I quickly prune whole portions of the world that I know shouldn’t be rendered.

    Even better, then when I step inside the room, I trim the entire rest of the world from the tree and then only render the room and all its descendants.

    I think a lot of the design decisions that the JMonkeyEngine team made were based on things in David Eberly’s book, 3D Game Engine Design. I don’t know the technical details of how to implement an approach like this, but I bet this book would be a great starting point for you.

    Here is an interesting article on some different culling algorithms:

    • View Frustum Culling
    • Back-face Culling
    • Cell-based occlusion culling
    • PVS-based arbitrary geometry occlusion culling
    • Others
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