I have a model in Blender 2.93. I am exporting it to JSON using landon I am then importing the JSON into a WebGL rendering layer and feeding directly to shaders

The JSON UV export is an array of floats between 0 and 1

The shaders look like:


       precision mediump float;
       attribute vec3 position;
       uniform mat4 model, view, projection;
       attribute vec2 uvs;
       varying vec2 vUv;
       void main() {
          vUv = uvs;
          gl_Position = projection * view * model * vec4(position, 1);


      precision mediump float;
      varying vec2 vUv;
      uniform sampler2D tex;
      void main() {
         gl_FragColor = texture2D(tex,vUv);

The model in blender looks like: model in blender

The model imported in the engine looks like: enter image description here

I need ideas for next steps to debug the the UV issue with the texture. The texture seems to load okay but the UVS are off. Is there some conversion step from blender I'm over looking?

Update #1:

per @DMGregory in the comments updating the vertex shader to the gl_Position = vec4(uvs.xy * 2.0 - 1.0, 0.0, 1.0)

The engine UVS looks like the following: enter image description here

We can compare this to the UV Mapping from blender: enter image description here

Update #2 Model loading:

I am using the regl webgl frame work to load the model data. The UVS are in a flat 1D JSON Array and get bound to the shaders as an regl attribute

Here is example JSON of the model: https://gist.github.com/kevzettler/648cb509d8f4f5a383696449eced96a2

  • 1
    \$\begingroup\$ Have you tried outputting vec4(uvs.xy * 2.0 - 1.0, 0.0, 1.0) as your vertex position, to visualize the UV unwrap as seen by your importer? It may also help to show us your model loading function so we can see how you're interpreting the UVs. \$\endgroup\$
    – DMGregory
    Commented Dec 10, 2021 at 2:28
  • \$\begingroup\$ Thanks for that suggestion @DMGregory I have added the UV unwrap shader output to the post and comparison to the Blender UV map. It seems the engine UV's maybe upside down?. I have also added notes on the Model importing. Let me know if you have further thoughts much appreciated. \$\endgroup\$
    – kevzettler
    Commented Dec 12, 2021 at 19:16
  • 1
    \$\begingroup\$ Oof. It's hard to say without the wireframe lines, but it looks like there's little to no correlation between the expected UVs and what your shader is receiving. It might help to export a simpler model - like a single quad or standard cube, then walk through each data transformation along the way, comparing the JSON text / debug visualization against a small number of expected values. \$\endgroup\$
    – DMGregory
    Commented Dec 12, 2021 at 19:17
  • \$\begingroup\$ @DMGregory I have a hunch. I have added the JSON of the model to the post. The json includes separate indicies for position, normal, and uvs, based on the post at gamedev.stackexchange.com/questions/19625/… I suspect I need to massage the UVs so that they are arranged in an order that corresponds with the vertice position index. Does this make sense? \$\endgroup\$
    – kevzettler
    Commented Dec 12, 2021 at 22:46
  • 1
    \$\begingroup\$ That sounds like a testable hypothesis. \$\endgroup\$
    – DMGregory
    Commented Dec 12, 2021 at 22:50


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