3D Gaussian Splatting, Meshes, and Voxels: What's the Difference
Choosing the Right Format for Walkable 3D Scenes
Introduction
You've scanned a room. The textures look stunning — sunlight through the window, shadows in the corners, every detail sharp. You drop into first-person view, take a step forward, and immediately fall through the wall into a void.
This is the reality of working with 3D data today: how you represent a scene determines everything you can do with it. A format that delivers breathtaking photorealism might completely fail at basic interactions like collision detection. A format that lets you walk through walls might be the same one that captures light perfectly.
The three dominant representations — 3D Gaussian Splatting (3DGS), polygonal meshes, and voxels — each solve different problems. There is no "best" format. There is only the right format for what you need to accomplish.
This article breaks down how each representation works, where each excels, where each falls short, and how to choose between them — especially if your goal is a walkable, photorealistic 3D scene.
1. How 3D Data Is Represented: A Quick Overview
Before diving into specifics, let's define the three formats at their most fundamental level.
| Format | Description |
|---|---|
| 3D Gaussian Splatting (Point Cloud) | Millions of semi-transparent ellipsoids (Gaussians), each carrying color, position, opacity, and covariance. Together they form a continuous, photorealistic scene. |
| Mesh | A network of vertices, edges, and polygonal faces (usually triangles) that define the surface of an object or scene. Textures are mapped onto these surfaces via UV coordinates. |
| Voxel | A 3D grid of cubic cells, each holding a value — occupied or empty, with optional color and density data. The 3D equivalent of a pixel. |
Each format comes from a different lineage. Point clouds came from laser scanning and photogrammetry. Meshes came from computer graphics and CAD. Voxels came from medical imaging and scientific visualization. Today, they're all converging in applications like virtual tours, digital twins, and 3D content creation.
Why representation matters: Your format choice cascades into every downstream decision — can you edit individual objects? Can you detect collisions? Can you stream the scene over a browser? Can you measure distances accurately? Answering these questions starts with understanding what each format does and doesn't offer.
2. 3D Gaussian Splatting (3DGS): The New Standard for Photorealism
2.1 What Is 3D Gaussian Splatting?
3D Gaussian Splatting, introduced by Kerbl et al. in 2023, represents a scene as a dense collection of 3D Gaussians — soft, anisotropic ellipsoids that overlap to form a continuous image when rendered from any viewpoint.
Unlike traditional point clouds where each point is a hard, infinitesimal dot, each Gaussian has:
- Position (xyz): Where it sits in 3D space
- Covariance (3×3 matrix): Its shape — stretched, flattened, or spherical
- Color (RGB): Encoded as spherical harmonics, meaning color shifts naturally with viewing angle
- Opacity (α): How transparent or opaque it is
When you render a 3DGS scene, the renderer sorts all Gaussians by depth, then composites them front-to-back — a process called "splatting." The result is a continuous, hole-free image that captures fine details like reflections, translucency, and specular highlights far better than textured meshes.
2.2 Why 3DGS Outperforms Traditional Methods
| Capability | 3DGS | Photogrammetry (Mesh) | NeRF |
|---|---|---|---|
| Photorealism | Excellent (view-dependent lighting) | Good (limited by texture resolution) | Excellent |
| Reconstruction Speed | Fast (minutes) | Slow (hours with manual cleanup) | Very Slow (hours to train) |
| Real-time Rendering | Yes (30+ FPS on consumer GPU) | Yes (game engines) | No (requires inference) |
| Training Data Required | 50-200 images | 50-200 images | 50-200 images |
| Editability | Limited (emerging tools) | Extensive (mature tooling) | Very Limited |
3DGS has rapidly become popular because it delivers NeRF-quality visuals at mesh-level rendering speeds. For applications like virtual tours, e-commerce 3D displays, and digital heritage, it's become the go-to approach.
2.3 The Limitation: No Solid Surfaces
Here's the catch: a 3DGS scene is a collection of fuzzy, overlapping ellipsoids, not solid geometry. There is no "surface" concept, no boundary between "inside" and "outside."
In practice, this means:
- A raycast goes through the scene without hitting anything definite
- First-person collision doesn't work — your camera drifts through walls and floors
- Physical simulation (gravity, rigid bodies) has nothing to collide against
- Measurement and annotation tools need to infer surfaces algorithmically
This isn't a bug — it's a trade-off. 3DGS prioritizes visual fidelity over geometric explicitness. For third-person viewing, turntable product displays, or fly-through videos, this is fine. For first-person walkthroughs where you want to walk up to the kitchen counter without falling through the floor, it's a problem.
3. Meshes: The Industry Workhorse
3.1 How Polygonal Meshes Work
A mesh is a collection of vertices, edges, and faces that define the explicit surface of a 3D object. Most meshes are made of triangles because triangles are always planar — three points always define a flat surface, which makes rendering and physics calculations predictable.
A mesh stores:
- Vertex positions (3D coordinates for each corner point)
- Face indices (which vertices form each triangle)
- UV coordinates (how a 2D texture maps onto the 3D surface)
- Normal vectors (which direction each face points, used for lighting)
Meshes are the native language of every game engine, 3D modeling tool, and GPU. When you play a video game, every object on screen is a mesh.
3.2 Strengths: Collision, Editing, and Engine Support
The explicit surface definition gives meshes several critical advantages:
- Collision detection is built-in. Every game engine can test whether a point intersects a mesh triangle. Walk up to a wall and you stop.
- Mature editing ecosystem. You can select individual faces, push vertices, unwrap UV maps, and apply materials — all with tools refined over 30+ years.
- Standardized. OBJ, FBX, glTF, USD — meshes are universally portable across tools and platforms.
- Efficient for hard-surface objects. For architectural geometry, manufactured parts, and anything with clean edges, meshes are ideal.
3.3 Weaknesses: Reconstruction Complexity
The problem with meshes appears when you try to create them from real-world scans:
- Photogrammetry produces noisy, over-tessellated meshes with millions of unnecessary triangles and topology errors
- Manual retopology (reducing and restructuring the mesh) is time-consuming skilled work
- UV unwrapping and texture baking add hours to the pipeline
- Transparent, reflective, and thin structures (glass, foliage, hair) don't reconstruct well
- View-dependent effects (specular highlights shifting with angle) are baked in, not dynamic
For a single product shot in a controlled studio, photogrammetry-to-mesh can work well. For an entire room or building with complex lighting and materials, the pipeline becomes prohibitively slow.
4. Voxels: Minecraft Blocks Meet Reality Capture
4.1 What Are Voxels?
A voxel (volume pixel) is a value assigned to a point in a regular 3D grid. At its simplest: occupied (1) or empty (0). In practice, each voxel can store color, density, material type, or any other per-cell data.
Think of a voxel representation as a 3D spreadsheet where each cell has an address (x, y, z) and a value. The grid is uniform — every cell is the same size — which makes spatial queries (is this point inside something?) extremely cheap.
4.2 When Voxels Shine
The uniform grid structure gives voxels unique advantages:
- Trivial collision detection. Check if the grid cell at position (x,y,z) is occupied. Done. No ray-triangle intersection math needed.
- Guaranteed solidity. An object defined as a set of voxels has a clear inside and outside. You can't "fall through" a voxel surface.
- Boolean operations are simple. Union, subtraction, intersection — carving a door into a voxel wall is straightforward.
- Volumetric data is native. Things like density, temperature, material composition — voxels handle these naturally.
These properties make voxels ideal for medical CT/MRI visualization, scientific simulations, and — increasingly — for interactive 3D scenes where collision fidelity matters.
4.3 The Resolution Trade-off
The downside of voxels is memory. Storage grows with the cube of resolution:
| Grid Resolution | Voxel Count | Storage (1 byte/voxel) |
|---|---|---|
| 256³ | 16.7 million | 16 MB |
| 512³ | 134 million | 134 MB |
| 1024³ | 1.07 billion | 1 GB |
| 2048³ | 8.6 billion | 8.6 GB |
For a room-scale scene at architectural precision, you might need 1024³ or higher. At 2048³, you're pushing into territory that requires specialized data structures (sparse voxel octrees, SVO) to manage.
Visual quality is also bounded by resolution. A curved surface looks blocky at low resolution and smooth at high resolution — but you pay exponentially for each step up.
5. Head-to-Head Comparison: 3DGS vs Mesh vs Voxel
5.1 Comparison Table
| Dimension | 3DGS (Point Cloud) | Mesh | Voxel |
|---|---|---|---|
| Photorealism | Excellent (view-dependent) | Good (texture-limited) | Fair (resolution-limited) |
| Reconstruction Speed | Fast (minutes) | Slow (hours+ with cleanup) | Moderate |
| Realtime Rendering | Yes (GPU rasterization) | Yes (game engines) | Yes (ray marching) |
| Collision Detection | No (no surface definition) | Yes (per-triangle) | Yes (per-cell, trivial) |
| Editability | Limited (emerging tools) | Extensive (mature ecosystem) | Moderate (boolean editing) |
| File Size (room scale) | 50-200 MB | 20-100 MB (optimized) | 16 MB - 8+ GB |
| Physics Simulation | No | Yes | Yes |
| View-Dependent Effects | Native | Baked | Difficult |
| Streaming Over Web | Good (WebGL viewers) | Good (glTF) | Variable (size-dependent) |
| Measurement Accuracy | Good (if dense) | Excellent | Grid-resolution limited |
5.2 Which Format for Which Use Case
| Use Case | Best Format | Why |
|---|---|---|
| E-commerce 3D product display | 3DGS | Fast to capture, looks stunning, no collision needed |
| VR game with physics | Mesh | Engine-native, collision + physics out of the box |
| Virtual property tour (fly-through video) | 3DGS | Maximum visual quality, rendering is smooth |
| Virtual property tour (free-roam walk) | 3DGS + Voxel | Visual quality + collision from voxel layer |
| Heritage documentation | Mesh or 3DGS | Depends on priority: accuracy → mesh, speed → 3DGS |
| Medical imaging | Voxel | Volumetric data is native to the domain |
| Architectural BIM | Mesh | CAD-native, dimensionally accurate |
| Indoor navigation with collision | Voxel or Mesh | Both provide explicit surface geometry |
The pattern is clear: no single format handles everything. The best results come from combining them — which is exactly what the next section covers.
6. From 3DGS to Walkable Scenes: Aholo3D's Approach
6.1 3DGS as the Core Pipeline
Aholo3D is built on a 3D Gaussian Splatting foundation. The platform takes images or video as input, reconstructs a photorealistic 3DGS scene in minutes, and provides a full suite of editing tools — crop, measure, annotate, generate fly-through videos, and export to PLY or SPZ. All of this runs through a web browser, with cross-device sync.
The 3DGS pipeline is the backbone of every feature: input → reconstruction → editing → export. It's what delivers the visual quality and speed that define the platform.
6.2 The Walkthrough Gap
But as discussed in Section 2.3, pure 3DGS scenes lack surface definitions. When you switch to first-person mode and try to walk through a scanned living room, there's nothing stopping the camera from passing through the sofa, the wall, or the floor. For fly-through videos and orbital viewing, this doesn't matter. For an immersive, free-roam walkthrough where the user controls where they go, it's essential.
6.3 Voxel Conversion: An Optional Layer for Walkable Scenes
To address this, Aholo3D is developing an optional 3DGS-to-Voxel conversion feature (currently in internal testing). The idea is simple: maintain the full 3DGS scene for visual rendering, but overlay a voxel grid as a collision mask for first-person navigation.
Here's how it works:
- Reconstruct the scene as 3DGS — full visual quality, fast turnaround
- Optionally convert to a voxel representation at a user-selected resolution — for specific scenes
- Walk through the scene in first person with collision detection powered by the voxel grid
6.4 The Best of Both Worlds
This approach is not about replacing 3DGS with voxels. It's about giving users a choice: want to fly through a scene and admire the visuals? Pure 3DGS. Want to walk through a scanned apartment as if you were there? Enable the voxel walking mode.
The core pipeline remains 3DGS. The voxel conversion is a value-add for specific use cases — virtual property tours, museum walkthroughs, construction site inspections — where first-person navigation with collision is the difference between a demo and a usable tool.
7. Real-World Use Cases
7.1 Virtual Property Tours
Real estate has embraced 3D tours, but most are stitched-together 360° photos that teleport you between fixed points. With 3DGS, you get seamless, photorealistic room-scale rendering. With the voxel walking mode, you can walk freely from the kitchen to the living room without falling through the floor — a true sense of presence that 360° tours can't match.
7.2 Museum & Heritage Digitization
Museums need both visual fidelity and interactive exploration. 3DGS captures the subtle lighting of a gallery and the fine details of artifacts. The optional walkable mode lets visitors explore virtual exhibits with natural navigation constraints — they stay in the corridors, not inside the display cases.
7.3 Architecture & Construction
For construction progress tracking, 3DGS delivers fast, photorealistic site captures. Site managers can visually inspect a floor from any angle. When they need to walk the floor plan as if on-site, the voxel mode provides grounded, collision-aware navigation — useful for remote inspections and client walkthroughs.
7.4 Game Level Design & Pre-visualization
Real-world locations scanned with 3DGS can serve as reference or blockout material for game levels. Designers can export the layout, study spatial flow, and use the voxel representation as a starting point for gameplay collision meshes — bridging the gap between real-world capture and game-ready geometry.
8. FAQ
8.1 Can you walk through a 3D Gaussian Splatting scan?
In a pure 3DGS viewer, you can move the camera anywhere — but there's no collision detection. The camera will pass through walls and objects. Walkable 3DGS experiences require an additional geometry layer (such as a voxel grid or mesh) to enforce physical boundaries.
8.2 What's the difference between point cloud and mesh?
A point cloud is a set of discrete points in 3D space, each with a position and (usually) color. There is no connection between points. A mesh connects these points into a continuous surface of polygonal faces. Point clouds are faster to generate from scans; meshes are easier to edit and use in game engines.
8.3 Are voxels better than meshes for walkthroughs?
It depends on the source. For scenes reconstructed with 3DGS, voxel conversion is typically faster than generating a clean mesh — you avoid the retopology/texturing pipeline. Meshes are better when you need to edit individual objects or export to a game engine. Voxels are better when you just need reliable collision detection with minimal processing.
8.4 How do you convert point cloud to voxel?
The process involves overlaying a 3D grid onto the point cloud and marking each grid cell as occupied if it contains enough points above a density threshold. With 3DGS specifically, you sample the Gaussian distributions at each grid cell's center — if the accumulated opacity exceeds a threshold, the cell is solid. The output is a binary (or density-valued) 3D grid usable for collision detection.
8.5 What is 3D Gaussian Splatting best used for?
3DGS excels at capturing and rendering real-world scenes with high photorealism. Its best use cases are virtual tours, e-commerce product visualization, heritage digitization, and any scenario where visual quality matters more than geometric editability. It's also increasingly used as a capture format that feeds into other representations (meshes, voxels) for downstream applications.
9. Conclusion: Choosing the Right Format for Your Project
3D Gaussian Splatting, meshes, and voxels are not competitors — they're tools with different strengths. The question isn't which one is best, but which combination gives you the results you need.
- If you need maximum visual fidelity in the shortest time: 3DGS is your answer.
- If you need deep editing, physics, or game engine integration: Meshes are the standard.
- If you need reliable spatial reasoning and collision: Voxels deliver simplicity and robustness.
- If you need everything — visuals, collision, and walkability: Combine 3DGS for rendering with a voxel collision layer.
That last combination is where much of the industry is heading: capture the world in the most visually faithful way possible (3DGS), then add structured geometry where interaction demands it (voxels or meshes). It's not about choosing one format — it's about knowing when to use each.