What is the reason why the same code version 4.2.1 can run but 6.49.0 cannot?

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Does this work as expected - Shader Effect Problem | Babylon.js Playground (babylonjs.com)?

attributes are not supported in fragment.

It is a lucky coincidence it worked in 4.2.1 :slight_smile: I would suggest removing the unused attribute line https://playground.babylonjs.com/#1ASENS#355