A toon (or cel) shader creates a cartoon-like image.  A common approach to toon shading is to limit the output colours to a set of fixed intensity levels, implemented in a fragment shader.

Try writing your own toon shader to output three different levels of red based on the light intensity (fIntensity) at the fragment.  For example,

• if the intensity is greater than 0.75, output pure bright red (r = 1).
• else if the intensity is greater than 0.5, output medium red (r = 0.6)
• otherwise, output dark red (r = 0.3)

Hint:  Output colour (call it fragColour) is a vec4 – the last component is 1.0, i.e., (R, G, B, 1)

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