Hi! Recently I've been wondering how can I set up a curve to manually control fresnel effect?
I got this idea from a tutorial which implemented this method in V-ray 3Ds MAX. Like what's illustrated in the attachment image, the origin point of "X-axis" represents the "center" of the rendering object, the infinity of "X-axis" represents the "edge" of the object. And the "Y-axis" is the output color(brightness), and you plug this curve into the "Reflection color" channel, you get the fresnel effect.
Is there any way to do this in Houdini? Thanks!

If you mean by possible in houdini you mean possible with mantra, then yes--sort of. Mantra does Fresnel computations at the bsdf level when using the principled shader. However it's still possible to disable the bsdf's Fresnel and post multiply by an arbitrary function. To use a custom ramp, connect the N dot I result into a Ramp Paramter's input, and multiply the reflect bsdf by the ramp value. This assumes the material is being build from scratch with atomic nodes and not starting with a premade shader like the principled.