Milky glass in render.

I have an hour and 40 minutes left in my render and I was wondering if the glass will become less milky? Why is the glass milky and what should I do to make it less milky? I have an 16k hdri image in the background and trilites in the room with area lights with a setting each of 15.000. Thanks


I guess in my next render I have to turn my transparency up for the glass. Right now it is at 0.559. Which way do I adjust it? I will change it and do a test render to determine that. What about IOR?


I set my transparency to 0.900 and things are looking good now. Should I have gone to 1.000? I will post a picture in the morning. Thanks.

ior shouldnt be less than 1.0.

You can render a small region to check your materials. Ctrl+b defines the render region, ctrl+alt+b clears it while in the viewport or looking through the camera. You should check your materials this way before a longer render. Glass material can be made using a simple Glass BSDF node, however, that will require calculations unnecessarily complex in case of window glass. Glass is not visible in windows, we see reflections and that is it. Dirt on the glass can be visible, but things like color, light absorption or refractions are not visible in clear glass windows so there is no point in calculating them in this case. You can make a material mixing completely transparent Transparent BSDF with sharp Glossy BSDF by a factor from Fresnel node. It’s easy to exaggerate the reflections by adding to the factor. It’s common for the glass to be double in windows, so you could as well have two planes in there for the reflections to be more realistic.

Thank you Daedalus and MartinZ. I have been rendering with my ior set at .400. I will look up what ior does, and then change the value to 1.000 and do some cropped test renders. I changed my transparency to 1 because I was getting a reflection off my curved tiles from outside my window. It made my render look like I had a vertical mullion right next to the edge of my window. For some reason my hdri darkened partway thru my render. Why would this happen? The third picture is reduntant.



The glass material I used is from PBR 3 fom this website. Thank you wolf.

By checking Simplify under Scene and setting AO bounces to 3, I cut my render time down from 2hrs 57 min to 2hrs 5min. 3000 samples

OK, so we are almost there to get to default Glass BSDF. IOR is index of refraction. It’s a value that defines how much the light bends going from one material to another. In case of air and glass it’s around 1.45 or higher depending on the specific kind of glass. You will get better results with the default Glass BSDF if you do not change any settings.

Thanks MartinZ. I will post a new render in a little over 2 hours. I repositioned my sun and set it’s value to 3 and turned my HDRI up to 3 as well. I will be placing a couple of lamps, a sofa I modeled and a coffee table and book in this scene for now but maybe not for a few days. As well I will be adding some flooring and baseboard.The Sofa can be seen in this scene at this web address. Then I will post it in the Gallery. The HDRI used in this render is from Greg Zaal. It is called Sunny Vondelpark. The HDRI in the sofa scene is also from Greg.

Here is my final render which I will post in the gallery. Why are their lines running across the floor boards? The most noticeable is running out from the right side of the sofa in line with the last button. The torchieres are compliments of Andrew Price, the Blender Guru. The book as well. The HDRI is from Greg Zaal. The coffee table is from shocky at this web address.


Oh, so this is inside… The outside is too dark. It’s a lot brighter outside than inside durnig the day. In fact it will be from 10 to 1000 times brighter if you measure the luminance. Right now it’s the other way around so I thought we are looking at the exterior. The windows have no handles as well. It’s a good start, however I think it still needs a lot of work to be moved to the gallery.

MartinZ, is there a tiling problem with the floor texture. I will do what you said. And add more furniture. Such a big room , it needs to be filled more. Thanks

The cherry leather chairs are compliments of Andrew Price, Blender Guru, as is the book and the torchiere’s. The coffee table is from shocky at this web address. The HDRI is from Greg Zaal. The sofa, window and room are created by me. Textures I used are from Poliigon.


The window is still quite too dark. In reality, windows get overexposed and almost completely white if you take a photo, but it is very usual in interior photography to take HDR photos or to or use Photoshop to make windows to still show detail. Anyway, they should be as bright as possible to look more realistic. When you make them bright enough chances are they will need to be desaturated as well. I usually even add a glow around them to get a nice result. Have a look here. Artificial lighting can produce 4000 lux of illuminance say on a work desk, but this is extremely bright, people rarely want this amount of light in their living rooms. Usual office brightness on a desk is around 200 lux, 50-100 lux is enough of light in a corridor for example. Now outside on a sunny day it can be 100 000 lux on the ground. In the shade of trees on a sunny day that we can see through your window the illuminance on the ground can easily reach 10 000 lux. Inside there should be no more than 400 on the floor. So there should be at least 25 times more light outside than inside. You may not want to be 100% correct and leave the detail in, but this is way too dark still.

Martin my HDRI is set at a power of 6 in the last render. Where do you think it should maybe set at. I will try some test renders. Can you see the white line in the floor coming out from the sofa towards the viewer, on the right hand side. What do you suppose that is?

The line could be a lot of things. The first thing I would check would be the material nodes, geometry as well, maybe some issue with normals? Worst case scenario if I could not determine the cause, I would just delete the floor and the materials and remake it. It should not take too long.

The number for the strength is hard to guess. The idea is to find it testing. Are you using filmic color management? I would set it to 100, then if it’s too bright to 50, then if its still too bright to 25, then let’s say it’s not bright enough with 25, then to 38 and so on. It will affect the lighting in the scene probably, you will need to see how that goes - if you like it. Or you could use light paths node to have one setting for the lighting another for what the camera sees if needed. It’s hard to talk about it without knowing whats the lighting set up in the scene. I do the background in the windows in post processing myself, I just take care of the light I want to come from the windows, and then render them black with reflections and not casting shadows so they don’t interfere with the lighting, then I composite whatever picture I want outside on top of it. But it doesn’t always need to be so complicated as I make it for myself…

Glass for architectural should not use refractive glass at all. For windows even the total internal reflection effect of the edge is never seen, and effects from refraction are negligible. Better off using transparency mixed with glossy, using either a layer weight/facing or fresnel node to drive the mix. If using flat planes (without a volume), fresnel IOR needs to be 1/IOR for the backface. IOR for glass is about 1.65, but the typical effect from this on flat window panes is how reflective it gets. The only time I use refraction is if I need frosted look, in which (on flat planes) I will also use incoming normal.

In the final render, for all the work that you might have done “twiddling with the glass,” the glass is effectively not there at all. So, why bother to include it?

Ever-lazy sot that I am … I would probably omit(!) the glass from the render, and provide any additional effects needed using the compositor. And, perhaps, a combination of the Cycles and BI renderers in the process of getting to it.

Window-glass has two main effects on a scene:

  • It reduces the hue-and-saturation of whatever is seen “through” it, and
  • It might contribute specular-only reflections, which are almost-never mirror reflections.

You can very readily achieve this result “in post” by shooting a render that includes only properly-shaped and properly-placed curves to represent the glass-planes. Give these planes strong specularity if you need that. Otherwise, use the alpha-channel, possibly added with noise if you want the glass to be old. You now set up your compositing noodles to provide these two modifications to a render which did not originally include them. You can very-precisely adjust the final effect and do so very quickly since no re-rendering is involved.

If you do need the effect of a simple reflection (that no one is too-likely to challenge), you can simply take a single-frame render of whatever’s supposed to be “reflected,” flip it horizontally along the X-axis, and comp it in using the glass-planes as a combined mask, greatly reducing its hue/sat and possibly adding a bluish color cast.

In the old school, this would be “darkroom work,” and in those “photo-realistic” photos that you see in magazines and such it happens far more than you might realize. (In fact, I would say that you will never find an image where it wasn’t done.) The only thing that matters is the final image, and it behooves you to find the shortest and least-expensive possible way of getting to it.

I would not be able to agree to this. The reflections of the glass are important and often make it a lot more realistic. I have never seen renders that show windows but do not show reflections and look good. There is no need for inacurate and time consuming manual tricks in post processing when it is possible to get the actual real reflections. These are not the old days anymore and a whole lot of things are done differently these days. Brightly lit curtains or walls near windows often can be seen in the reflections very well as well as just the edges of the frames. The reflections are in fact sharp as the ones we see in mirrors so it would be very accurate to call them mirror reflections it’s just that Fresnel effect is very well visible in case of glass. The term ‘specular’ is not that relevant in renderers like Cycles. There is little distinction between reflection of an object and reflection of a light source in Cycles unlike in other renderers like Blender Render or Mental Ray. To be honest in my opinion this advise seems to bring more confusion than help.