Lesson 1, Material 0 Summary: Understanding Voxels in CS2's Smoke System

Key Concepts & Implementation Steps

CS2's smoke system uses voxels—tiny invisible cubes that form a unified 3D grid, enabling interactive smoke mechanics. Unlike traditional games that separate visuals from gameplay, CS2 stores all smoke data in one structure that every system reads from. Think of voxels as the 3D equivalent of pixels: while a pixel is the smallest 2D unit, a voxel is the smallest 3D unit. In CS2, each voxel (roughly 20-30cm per side) stores a simple binary value: smoke-filled or empty air.

This grid is comparable to Minecraft's block system, but with key differences. Minecraft voxels are visible blocks (1 cubic meter each, like a refrigerator). CS2's voxels remain invisible—the rendering engine reads voxel data and displays smooth, realistic smoke clouds. A typical 5-meter smoke grenade contains approximately 8,000 voxels (20×20×20). The genius is unified storage: when a bullet marks voxels as empty, the rendering system immediately displays a hole, the vision system allows sight through it, and the spreading system refills them gradually. All systems coordinate through this single source of truth.

The Payoff or Visual Breakthrough

You now understand that voxels create an invisible 3D grid storing smoke states. This unified approach enables automatic interactivity—bullets, grenades, and spreading all instantly affect every system because they all read from the same data structure.

Transition to the Next Challenge

The foundation is established, but understanding voxel theory is only half the battle. Next, we'll explore how computers efficiently store and access thousands of voxels in memory without degrading performance during 60+ frames per second gameplay.

Recap

You now understand that CS2's smoke system uses a unified volumetric approach where all systems read from and write to a single 3D data structure. This unified approach enables automatic interactivity—when a bullet changes smoke data, every system sees that change instantly.

The Foundation: What Are Voxels?

CS2's smoke system is built on voxels—tiny invisible cubes that fill 3D space. The word "voxel" comes from combining "volumetric" and "pixel," just like a pixel is the smallest unit of a 2D image, a voxel is the smallest unit of 3D space.

Here's what makes voxels special: each voxel is a small cube that can store information. In CS2's case, each voxel stores one simple piece of data—whether it contains smoke or not. Think of it as a tiny box that's either "on" (filled with smoke) or "off" (empty air).

CS2's Invisible 3D Grid

When you throw a smoke grenade in CS2, the game creates thousands of these voxels arranged in a massive 3D grid. Picture a checkerboard, but instead of being flat, it extends in all three directions—rows, columns, and layers stacked on top of each other.

This grid exists in the game world's 3D space, not on your screen. It's the invisible data structure that remembers where smoke is at every moment. Each voxel in this grid is roughly the size of a player's head—small enough to create smooth-looking smoke, but large enough that the computer can track thousands of them efficiently.

The entire smoke cloud area is covered by this grid. When smoke spreads, it's actually the game marking individual voxels as "filled." When a bullet creates a hole, the game marks specific voxels along the bullet's path as "empty."

How This Compares to Minecraft

If you've played Minecraft, you've already seen voxels in action. Minecraft's world is made of visible blocks—each block is a voxel that can be dirt, stone, wood, or air. You can see the individual cubes that make up everything.

CS2's voxels work on the same principle, but with two key differences:

Size: CS2's voxels are much smaller. A Minecraft block is one cubic meter—roughly the size of a refrigerator. CS2's smoke voxels are about 20-30 centimeters per side—small enough that you'd need hundreds to fill the same space.

Visibility: Minecraft shows you the individual blocks. CS2 hides the voxel grid completely. You never see the individual cubes—the rendering system reads the voxel data and displays a smooth, realistic smoke cloud. The voxels are just the invisible data structure underneath.

Why Voxels Enable Interactive Smoke

This voxel grid is what makes CS2's interactive smoke possible. Remember how traditional games separate visual effects from gameplay logic? They can't create bullet holes because the visual system doesn't know where bullets are, and the gameplay system can't change what you see.

CS2 solves this by storing everything in the voxel grid. When a bullet travels through smoke, the game calculates which voxels the bullet passes through and marks them as empty. Because every system reads from this same grid, the changes happen everywhere simultaneously:

• The rendering system sees those voxels are now empty, so it displays a hole
• The vision-blocking system sees those voxels are empty, so players can see through that area
• The spreading system sees those voxels are empty, so it can refill them gradually

The voxel grid isn't just a visual trick—it's the single source of truth that all systems use to coordinate.

The Scale of the System

To appreciate how impressive this is, consider the numbers. A single smoke grenade in CS2 creates a cloud that might be 5 meters across. With voxels sized at about 25 centimeters each, that's roughly 20 voxels in each direction.

That means a single smoke cloud uses approximately 20 × 20 × 20 = 8,000 voxels. The game tracks the state of every single one of these cubes, updating them as smoke spreads, bullets punch through, grenades disperse the cloud, and the smoke gradually refills.

And this happens for every smoke grenade on the map, all being calculated and rendered 60+ times per second during gameplay.

What's Next

You now understand that voxels are the invisible 3D grid storing which tiny cubes contain smoke and which are empty. Next, we'll examine how the computer actually stores and accesses this massive grid of 8,000+ cubes in memory without slowing down the game.