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glTF file size after Draco compression

See original GitHub issue

When I’m compressing the model using Draco: model.obj (8,000 KB) -> model.drc (204 KB)

Using glTF Pipeline: model.gltf (304 KB) + model.bin (8,000 KB) -> modelDraco.gltf (200 KB) + modelDraco.bin (865 KB)

So .gltf file is x5 bigger than .drc. Am I doing something wrong or just completely misunderstanding the purpose of the glTF file format?

I know it’s a silly question, but it can probably help beginners like me. Thanks!

Issue Analytics

State:
Created 5 years ago
Comments:5 (3 by maintainers)

Top GitHub Comments

1reaction

lilleysecommented, May 17, 2018

I’m not noticing any worse compression when using gltf-pipeline vs. draco executable. I checked that they use the same default compression options. The model I tested is the Stanford Dragon which contains positions, normals, and some objects with tex coords.

type	size
obj	7846 KB
drc	247 KB
gltf w/ draco JSON	8 KB
gltf w/ draco .bin	239 KB

dragon.zip

Check how many primitives your gltf contains - it’s possible that the obj->drac encoder is combing all mesh data into a single primitive and compressing that, whereas gltf-pipeline compresses each primitive individually. Feel free to upload your obj model as well.

0reactions

lilleysecommented, Jun 21, 2018

Make sure you are on the 2.0 branch when testing Draco.

But yes, the Draco glTF extension applies compression on a per-primitive basis and does not alter the hierarchy or combine primitives.

EDIT: there is one case where primitives may be split - if primitives have different materials but reference the same indices. See https://github.com/AnalyticalGraphicsInc/gltf-pipeline/issues/369#issuecomment-386841595. However I don’t think this is the issue you’re encountering.

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