Explain Hilight glossiness and Reflection glossiness

[tricky]

Usually, I adjust only the Reflection glossiness value to change how soft/blurry my reflections are. I wondered when people use the Hilight glossiness?

Can/should it be used to 'fake' blurry reflections whilst keeping the Reflection glossiness close to 1.0 (and hence rendering will be cleaner and quicker and require fewer subdivs)?

[Morbid Angel]

Hilight is specular or direct reflection (from lights), and reflection is indirect reflection, from surface to camera. In some cases, if you need to make layered shaders, or for custom control, you may want to disable specular reflection, so in this case you would uncheck lock between the two and set the hilight glossy to 1, which would mean there would not be any specular and only reflection would be rendered. For example if you wanted to create a layered shader where you had reflection and specular as separate layers, this would be a way to do that.
Generally speaking, you want to keep those locked as this would be more physically accurate, since in real world there is no specular, only reflection.

[Morne]

But then even though it isn't strictly physically accurate, would a shader with highlight 1 and glossy 0.65 render FASTER than a shader where the two is locked at 0.65?

and in reverse, what if the highlight is at 0.65 and the glossy at 1?

[Morbid Angel]

You can test it, but I don't think so. Since then the specular will be substituted with reflection entirely, remember that specular is made to speed up rendering, so having it off will most likely slow things down.

[Morne]

remember that specular is made to speed up rendering, so having it off will most likely slow things down.

It stands to reason then that highlight of 0.65 and glossy of 1 will render faster than the other way around, since you have stronger specular and less glossy in the 1st instance.

Will test this out when I have a moment.
Anybody else care to test it?

[tricky]

It stands to reason then that highlight of 0.65 and glossy of 1 will render faster than the other way around, since you have stronger specular and less glossy in the 1st instance.

Will test this out when I have a moment.
Anybody else care to test it?

This is what I would have hoped. When I get a spare moment, I will test.

[grantwarwick]

Hilight is specular or direct reflection (from lights), and reflection is indirect reflection, from surface to camera.

I should also note that Vrays Dome light breaks the two apart based on importance sampling as the vray image antialiaser handles the edges of specular noise well.

[stef.thomas]

I sometimes separate the two and keep highlight glossiness at 1.0 to get rid of an ugly spec highlight of sun/lights on ground or floor material. I'm not sure of the benefit of comparing render speed as they both control different things.