Creating a demo with a custom .obj file

I recently tried to compile this project with my own OBJ and MTL files. I want to make a Minecraft head that looks at the cursor. I made the model using Blockbench.
When I ran the "convert" function, I got a JSON file.
It looks like that:
```
{
"positions": [
[0.25, 0.5625, 0.25],
[0.25, 0.5625, -0.25],
[0.25, 0.0625, 0.25],
[0.25, 0.0625, -0.25],
[-0.25, 0.5625, -0.25],
[-0.25, 0.5625, 0.25],
[-0.25, 0.0625, -0.25],
[-0.25, 0.0625, 0.25]
],
"chunks": [
{
"color": [119, 57, 0],
"faces": [
[3, 6, 4],
[2, 3, 1],
[7, 2, 0],
[6, 7, 5],
[5, 0, 1],
[6, 3, 2]
]
}
]
}
```
It seemed kinda suspicious to me, as the built-in fox model is way bigger...
I built a "normal" demo, but no model displays on the page. What should I do? I'm not very familiar with the rendering system, but I'm sure that the fault lies with Blockbench or the conversion library (all the paths and filenames are correct, I've checked that already).

Start with the normal demo and the output of the "convert" function, then compare the custom OBJ/MTL conversion with the built-in fox model. Check how the rendering system consumes the generated JSON and whether the custom model is loaded by the demo. Done means the custom model appears on the page and follows the cursor as intended.

Written by the indexing model from the issue text.