Why are my triangles transparent?

Hello. How to make triangels not transpirient? Can you post link to any tutorial about it?

https://vimeo.com/387975739

The question is closed. It's just cull mode setting on the encoder. And a well ordered vertex triangel array.

       encoder.setCullMode(.back)
       encoder.setFrontFacing(.counterClockwise)
Why are my triangles transparent?
 
 
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