How can I optimize this render of a double-glass window?


(Janneman) #1

I’m working on this window render, and the render seems to need an unusually high amount of samples to be decent. Normally I render the foreground and background seperately, but in this case since it’s glass, I render both at the same time. Even rendering it at 10000 samples (with denoiser! still gives me some noise.
I didn’t play with the render settings yet, it’s all quite standard (which seems to work fine in most cases).
Any advice would be appreciated, as I’d like to reduce the render time for this since I need to render more similar windows later. I’d prefer to be able to get away with <500 samples.


(Emir Sinan Gürlek) #2

You can try using this addon: OptiX-Denoiser-for-Blender

More info about the addon at this topic.


(Janneman) #3

Whoa. This is really cool stuff. I’m trying it now, thank you!!


(English is not my native language) #4

Hi.
To try to reduce fireflies (hard white isolated spots) you try in Render tab, under Sampling > Settings, set Clamp Indirect=10. If that is not enough, reduce until Clamp Indirect=5, but not less than 5.


(Janneman) #5

Thank you! These render settings are an important part of Blender that I can no longer neglect.


(sundialsvc4) #6

But also, consider faking the glass. Look at what the glass is doing to the light to give the impression that “there’s a piece of glass here.” There’s a slight reduction in hue and saturation, a slight blue cast to the entire region, and a hint of a reflection.

One of my (conventional) photographic mentors kept saying to me, “Don’t look at the scene. Look at the light. It took me a long time to realize what he was talking about.

Sometimes you do need to “model physical reality,” and when you do, you generally can. But, sometimes you don’t. And if you don’t, you can save a tremendous amount of computer time. Seriously consider, “how important is this-or-that effect actually going to be?” “Is it going to ‘make or break the shot’ if I fake it, instead?”

  • “Ingrid, fake it.” – Alfred Hitchcock’s acting advice to Ingrid Bergman.

Remember also that you can combine renderers to produce a single shot most efficiently. Cycles is only one of the resources at your disposal.


(Janneman) #7

@sundialsvc4 I completely agree, this is very good advice. Thanks :+1:


(CarlG) #8

I’m a big fan of faking pretty much everything glass, such as making them single faced, transparent shadows etc. But if I were making a product shot of a glass window, I’d probably lower the use of fakes. A real glass windows could have two or three layers of glass with space between, that’s like 6 faces light has to pass through.

In this case, I’d probably do fresnel->refraction/glossy (glass shader) combined with transparency based shadow handling and use actual solid cubes for the layers of glass.


(sundialsvc4) #9

If I were doing a product shot for the manufacturer of such windows, I might conclude that absolute close-up realism is essential such that I would actually model the glass to get accurate refractions because that would be viewed as essential by the client who’s paying for all that computer-time.

But “actual glass” is something that you almost never have to do. I’ve watched lots of people here struggling with “sunlight pouring in through a window,” trying to get that sunlight to be what actually illuminates the room. I learned everything I needed to know about that sort of thing by assisting Arizona Highways photographers as they shot “a warmly sun-lit hotel interior” … at two o’clock in the morning on a new moon night. You absolutely couldn’t tell it, but all of the lighting in that centerfold photograph was fake.