The Complete JT to DGN Conversion Guide

Geometry Compression Support:

JT: Full support | DGN: No support

Impact:

Geometry compression describes the process of compressing the representations of a 3D model's geometry, usually a triangle mesh. 3D geometry compression does not change the topology of a 3D model, but just changes the way that a 3D model and its 3D positions and related vertex data is stored. Geometry compression can be lossy (just like JPEG compression in image processing can be lossy, for example), in which case one might notice slight artifacts like variations in 3D vertex positions (compared to the uncompressed 3D model). However, such differences are often not noticeable. There are only very few standards for geometry compression, like glTF's support of Draco compression and similar extensions.

Texture Compression Support:

JT: Partial support | DGN: No support

JT Notes:

JT stores texture images (typically as JPEG data) within binary segments, enabling compressed image storage. No GPU-level texture compression (e.g. BCn/DXT) is defined by the JT specification.

Impact:

Texture compression refers to a process of compressing 2D texture images for memory-efficient rendering (and sometimes for efficient transmission). The decompression of compressed texture data is therefore performed on-the-fly during rendering, so that it never has to be stored in unpacked form, but can be kept as-is in GPU memory. Formats supporting texture compression methods, such as the ones offered by glTF through KTX2 containers, therefore allow 3D models to use a smaller memory footprint on the client device during rendering. This can speed up rendering time, and also make it possible to store and use larger amounts of texture data than it would otherwise be possible.

Procedural Textures Support:

JT: Partial support | DGN: No support

JT Notes:

JT includes a generic shader/material node system that enables procedural-style texture effects. Full arbitrary procedural texture programs (e.g. GLSL) are not defined.

Impact:

Procedural texture allow the modeling of surface details through mathematical functions, along with artistic control over various parameters. Typically, they are used for patterns like wood grain or other semi-regular structures. Since they are not using any pixels as source data, procedural textures have, in principle, infinite resolution and are very lightweight to describe. In this example, a procedural texture is used to model the look of a wooden material. Without support for this feature, in this case, the wooden parts won't show any visible details.

Embedded Textures Support:

JT: Full support | DGN: Partial support

JT Notes:

JT fully supports embedding texture image data directly within the file as binary segments, making JT files self-contained.

DGN Notes:

Textures can be referenced or embedded

Impact:

Embedded textures allow the storage and exchange of an entire 3D model and its materials within a single file, by embedding the texture images directly into the 3D file (and not storing them as separate image files). Without support for this feature, textures have to be stored in separate image files, and referenced from the main 3D model file.

Normal Mapping Support:

JT: Full support | DGN: Partial support

JT Notes:

Normal maps are fully supported in the JT material specification with no stated limitations.

DGN Notes:

Basic normal mapping for visualization

Impact:

Normal maps are used to model shading differences that are arising from small geometric details on a surface, such as fabric structures, visible gaps between bricks forming a wall, or rough rock surfaces. In this example, a normal map is used to model a fabric structure. Without support for this feature, the rendered fabric will look smoother than it actually is in the real world, as the fabric structure won't be visible.

Standardized Format Support:

JT: Full support | DGN: Partial support

DGN Notes:

Open specification with some proprietary extensions

Impact:

Standardization plays a huge role in 3D model formats. With a format being standardized, every application will have a clear way of how to load or store data using this format. This makes it easier to re-use the 3D model across different applications, but also to make sure it will still be accessible and usable after a couple of years.