How can I have Alpha 0 but only shows highlight

Question

couldn't find tip on this. Maybe I was using wrong search terms.
I want to create "cartoon glasses". By that, I mean, a plane that is completely transparent, has no refraction effect, but we can see it's glare/highlights only.
When I apply "transparent" the highlights also lose their strength. If I use glass in Cycles, it distorts the pass-through light realistically (I just want it straight though, like transparent/alpha). If I use Evee --- well, Evee's a mess when it comes to glass. But I want the glare to move/live in the scene, not just be an image PNG pasted over it.
I'm still pretty basic in my Blender.

lemon · Answer

Using Eevee, you can use the "shader to RGB" node from a "glass" node. "shader to RGB" is like a prerendering from with we can get colors.

From it, we can use 2 color ramps: the first to control the light reflexion intensity and color and the other to control the level of transparency.

Color is given directly to the Principled and its alpha value is given by the intensity of the light.
Make sure to set the object transparent (alpha blend) in Eevee material settings.

Alternatively, you can also keep the original environment/light colors with this setting (look nicer, I think, but...):

How can I have Alpha 0 but only shows highlight

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