Generating 3D Data Textures for Volumetric Rendering in Three.js

Based on your requirements for creating volumetric textures from 3D models, I can provide some guidance using Three.js's data texture capabilities.

Using Data3DTexture for Volumetric Data

For your volumetric rendering needs, Three.js provides the Data3DTexture class which is specifically designed for 3D texture data. This would be more appropriate than trying to manually create and manage individual slices.

Basic Implementation Approach

Here's how you might approach this using Three.js:

1. Voxelization Process:

   • Create a 3D grid at your desired resolution (64x64x64)
   • For each voxel, determine if it intersects with your model
   • Store position and normal data in appropriate data structures

2. Creating the 3D Texture:

   • Use Data3DTexture to store your voxelized data

Here's a code example for creating a Data3DTexture:

JAVASCRIPTCopied
// Define your dimensions
const width = 64;
const height = 64;
const depth = 64;

// Create data arrays for positions and normals
const positionData = new Float32Array(width * height * depth * 3); // RGB for XYZ positions
const normalData = new Float32Array(width * height * depth * 3);   // RGB for XYZ normals

// Fill the arrays with your voxelized data
// ... (voxelization code)

// Create the position texture
const positionTexture = new THREE.Data3DTexture(
    positionData,
    width,
    height,
    depth
);
positionTexture.format = THREE.RGBFormat;
positionTexture.type = THREE.FloatType;
positionTexture.needsUpdate = true;

// Create the normal texture
const normalTexture = new THREE.Data3DTexture(
    normalData,
    width,
    height,
    depth
);
normalTexture.format = THREE.RGBFormat;
normalTexture.type = THREE.FloatType;
normalTexture.needsUpdate = true;

Voxelization Strategies

For the voxelization process, consider these approaches:

1. Raycasting Method:

   • Cast rays from multiple directions through your model
   • Record intersections to determine voxel occupancy
   • Sample position and normal data at intersection points

2. Signed Distance Field (SDF):

   • Compute the signed distance from each voxel to the model surface
   • This gives you both inside/outside information and proximity to surface
   • Can be used to reconstruct surface details in shaders

Shader Usage

When using these textures in shaders, you'll access them like this:

GLSLCopied
uniform sampler3D positionTexture;
uniform sampler3D normalTexture;

// In your shader:
vec3 position = texture(positionTexture, voxelCoord).rgb;
vec3 normal = texture(normalTexture, voxelCoord).rgb;

Exporting to KTX2

For exporting to KTX2, you might need to use additional libraries like ktx-parse or @loaders.gl/ktx since Three.js doesn't directly support KTX2 export. You would need to:

1. Convert your 3D texture data to the appropriate format
2. Use a KTX2 library to create the compressed texture
3. Save the resulting file

Troubleshooting Your Current Issues

Based on the issues you're facing:

1. Inaccurate voxelization: Consider using a multi-pass approach with raycasting from different directions to better capture the model's geometry.

2. Data mixing: Ensure your data is properly organized in memory. For a 64³ texture, each voxel should have a clear mapping to its position in the 3D grid.

3. Shader rendering issues: Verify your shader is correctly sampling the 3D texture using the proper coordinates and interpreting the RGB values correctly.

I hope this guidance helps with your volumetric rendering project. Let me know if you need more specific advice on any part of the implementation.