I notice the glass material that made with Mantra Surface is too slow for render, especially with environment map (I used Environment Light for it). Trying to optimize scene I have found glass material (see picture below), named as “Oglass”. I just have connected it's outputs to surface_output, set Index of Refraction to 1.2 and got nice glass material. Besides, it has turned out fast enough for render. Though this material doesn't interact with Environment Light's map, I have made sphere with texture for environment. I have some questions about it material. Why is it faster than Mantra Surface? And how can I read more about this material? The matter is that there is empty space in help about it.
Thank you!

Mantra surface was designed to give accurate results with the physically-based rendering engine, so it's bound to be slower because the calculations are more intensive. I'm not sure, but I bet the Oglass is a deprecated shader, meaning it's there only for compatibility sake.
I'd encourage you to use the mantra surface shader and tweak sampling and stuff to shave some time.

cheers

Thank you!
I had already see what qualitative result the Mantra surface can to create. Only why in Houdini there is no enough of ready materials based on Mantra surface at least to learn to create own materials on their basis. Besides, the fast result is sometimes necessary. It is interesting, whether the library of pre-made materials in Houdini 12 becomes richer how it was in Houdini 10?

I think the Mantra Surface is a recent development, maybe the lack of documentation comes from that. I find the parameters quite self-explanatory, although I agree that not everything works like I expect sometimes. Nevertheless, you can sill use it for 99% of the cases, most probably
Shader building is a huge topic and houdini provides a very low-level approach to it, which can be daunting for someone starting fresh. Most of the theory comes from a Renderman background, befor software came packaged with extensive libraries. Let's see, maybe they'll revamp the material library, who knows? I think there's also a workaround to get H10's material palette to show up on H11, search the forum and you should find it. I just can't guarantee that all of them will work nicely with PBR
Lastly, Digital tutors has a good section on Mantra rendering. Side FX has a nice tutorial on shading and rendering (intro though) and 3D Buzz has a nice extensive title on building an HDRI shader, might help.

Cheers

I certainly think there's nothing wrong with stripping down the mantra surface shader and rebuilding it > ie take out what you don't need.

rob