Graphics Reference
In-Depth Information
.json
Node hierarchy, materials,
lights, cameras
.bin
Vertices, indices, and
animations
.glsl
Shaders
.png, .jpg, …
Textures
Figure 2.1.
Set of files defining a glTF asset.
several transforms and transform representations per node; glTF only has one
transform per node and fewer representations.
We recognize that many engines will need features beyond what glTF de-
fines. For this, glTF is extensible to support engine-specific features by allowing
metadata on all JSON object properties.
2.3.3 Code, Not Just Spec
A spec alone is not sucient to make glTF successful. We believe that an
open-source content pipeline that converts COLLADA to glTF is important
for adoption. We developed such a tool, COLLADA2GLTF, as open-source on
GitHub [Khronos 14a]. COLLADA2GLTF provides developers an accessible on-
ramp for getting content into their engine and serves as a reference implementa-
tion for converters for other model formats. We selected COLLADA because of
our familiarity with it, its open-standard, and its widely available exporters.
To ensure that a glTF renderer is easy to implement, we developed several
glTF renderers while working on the spec, including JavaScript open-source im-
plementations in Three.js [Mrdoob 14], Cesium [Analytical Graphics 14], rest3d
viewer [AMD 14], and Montage with straight WebGL [Fabrobinet 14]. (See Fig-
ure 2.2.) In many cases, we implemented a renderer multiple times as spec work
progressed.
