Your browser does not support webgl, you should use google chrome
If you are on Windows with chrome, try the --use-gl=desktop option to start chrome.
Your browser lacks support for the OES_texture_float extension. There is several reasons why that might be.
- Firefox does not support OES_texture_float. You can use google chrome which does support it.
- The Chrome ANGLE wrapper for Windows does not support OES_texture_float. Disable the ANGLE wrapper by starting chrome with --use-gl=desktop
- Your graphics card may not support this feature
- Some Open Source drivers (like ATI for linux) do not support the OES_texture_float even if your hardware is capable
An unknown error occured
Your driver/hardware does not support texture lookups in the vertex shader. The grass cannot be rendered without that.