Specular in Cycles

I am having so much trouble getting specular highlights on glass materials using lamps in cycles. Anyone know why? I have a glass pillar in the center of the scene but I need to give it some highlights so that you can see it, but no matter where I move the lamp I’m not getting anything close to realistic highlights; not getting any highlights actually. It’s as if the glass material don’t reflect light from lamps.

In the object data for the lamp, have you checked ‘Multiple importance samples’ ?

I just tried that and it did have an effect. At least no the light is being reflected but nothing like a glossy material does. What does the Ray size do? I played with that making the value larger and it made the reflection of the point light bigger. Why does the glossy materials reflect perfectly but the glass materials don’t?

Glass is much different than glossy. It is a mix of transparent, and glossy depending on viewing angle, and then it also has refraction. You can always try mixing the glass with glossy using fresnal or facing as teh factor. But I honestly don’t have any idea what your render/nodes looks like and what effect you are going for. At the least post a quick render/node setup and also a reference photo showing the effect you are trying to capture.

Some rndom ideas:
It is possible that using mesh lights will help, just use a plane with emission material instead of lamps.

it is possible your glass has no thickness or is not a closed solid. It really should be closed/mainfold, if not try a solidfy modifer.

It is possible you have unchecked ‘caustics’ in render settings.

make sure your scales are applied, and the glass has no doubles, recalc your normals. Glass renders bizarre with doubles.

Glass has a lot fo gloss and therefor you really should be using some environmental lighting, if only weakly. In general it will look 10 - 15 times better than just some rgb background.

Who knows? post some images and/or the blend with a fuller expanation of what you want.

One thing I like to do when I am stumped is to check out a .blend of someone who did what I am trying to do very well. There are some great glass renders on blendswap.com. Here is one that I like: http://www.blendswap.com/blends/view/27362. Maybe open that up and see if you can learn a thing or too.

Brent, I have had the same problem… I think Blender allday hit upon your answer … make a mesh light, make the material emmission and give it a try. I really wonder if there is an issue, because I can’t even get the blender spot lights to reflect or even except the light even on certain glossy materials.

I’ve been using blender for years. I know how it works pretty well. Every since the last update glass has been giving me trouble. I made a glass thing before the last release and it was very simple. Now I go back to make a tutorial and glass is all fucked up.

Here check out this video I did as a teaser to the upcoming tutorial. http://www.youtube.com/watch?v=9AliCojLAsY

Now the specular isn’t very noticable and hell, maybe it isn’t the specular at all that is giving me issues, but I am having a hell of a time recreating that VERY simple scene now. I can’t get the glass pillar to look that 3d anymore. It looks more like a transparent or something. Won’t give highlights on the corners. It’s just very odd. Glass just behaves differently. I need to take a look at the release notes.

I just opened the .blend that I did that video with and it renders out fine. I did notice that I had used an IOR of 1.2 and when I was trying to recreate it I was using 1.45, so maybe that caused some of it, but I know there is something different about the glass material shader.

I know I’m supposed to link lots of info with pics and such in the first post. I just hoped it would be something simple that wouldn’t require me to do all that. Thanks for trying to help anyway. If anyone has any ideas, post em.

Alright I’ve been playing around with it and I can not for the life of me figure out how to highlight the edges to bring them out and define them. Here’s a picture of the set up and result I’m getting. I seem to be getting very clear reflections from my environment map, but nothing from my emission plane.

Try putting lights on the sides, or even a rim light.

Try using an environment texture.
n/m, just saw you were.
You may just not have it at the right spot. Move it real close to teh glass and turn off ray visibility for the camera.

Rich has a point, you say you are using an environment texture / lighting , but I am not seeing it at all in reflections or refractions.

Look closer. It’s plainly visible.

Yeah I finally just gave up on getting the glass shader to behave like glass and just went with a mix shader of glass and glossy. Something changed in this last release in respect to light rays or something. I feel like it was unintended as well. But I guess it was a bit much to hope for a single shader that did a good glass material.

I challenge anyone to make a glass cube in cycles that looks like a glass cube. It’s driving me FN nuts!

Just to be sure and to make your challenge a little bit more tangible: This is the kind of look you’re after (for everyone too lazy to follow the link: that’s a studio photo of a glass cube)?

Infinity small light cannot be seen as specular reflection using path tracer, you need non zero aperture camera and light tracer (or bidir) for that. Not a bug, just limitation of method used in Cycles. Only mesh with emission and/or background as light source will work in every possible scenes.

I thought that cycles lights only appear in glossy reflections if you set the roughness higher then 0. In a perfect reflective material they don’t appear.

Had a little try on this task… I have a feeling this is rather a lighting than a shading challenge. The placement of the lights is more important that anything in scenes with glass - and the least logical postition for a light source is exactly the one that highlights the edge you’ve been hunting down for hours…:smiley:

This is a refraction/glossy mix shader - and almost too reflective if you ask me. Got some kind of plexiglassish look…

Scene file.


well done IkariShinji. I see you at the very least beveled the edges. Man I just looked at your .blend. Sheesh! That is a pretty complex scene for just a cube. You did get a very good result though. Do you think you could have done this using the glass shader? I have made beautiful glass using nothing but the glass shader in the past but suddenly it feels different. Look at this image: http://brentnewton.deviantart.com/art/Nixie-Tube-2-0-409402868?q=gallery%3ABrentNewton%2F26516789&qo=7

That is pretty damn good glass even if I do say so myself. Actually I don’t so much have issues with any shape but a cube… er flat glass faces I mean. One more thing that is driving me nuts. How in the hell did you get that shadow to be less than 100% opaque? All my glass shaders produce dark shadows.

man thanks a lot. I am studding your .blend. I’m pretty new to cycles as compared to blender render. Are you a photographer or videographer? That lighting set up is great. I’m working on a tutorial. Even if I don’t use your lighting set up, I’ll reference you as being a huge help.

I tried using just the glass shader, but made basically the same observation as you: It seems to be a tad low on the reflection side. Apart from that, I feel the glass shader alone often seems to be a little dark.

In general I see the Cycles shaders as very basic building blocks. If Cycles is about realism, the materials have to be realistic, too. And in reality there is hardly any material e. g. just diffuse or just glossy. Using any one shader alone is therefore just lazy imho…:eyebrowlift2:

And talking about realism: Beveled edges are a must, especially for scenes that close up.

I agree…:smiley: And yes, I found the cube to be tricky, too. I think this is due to the very special nature of glass as reflective and refractive. Rounded glass shapes catch far more interesting light angles and reflections from the surrounding environment than a cube with it’s very strict and limited geometry. That’s why the edge bevel makes such a huge difference: Such a tiny strip of rounded geometry catches more light than the rest of the cube.

Hmm. I did nothing special to achieve that. Could scale be an issue here? I tend to model roughly to real world scale: It will surely make a difference if the light rays have to travel through a cube 10 cm thick vs. a cube 10 m thick?

Thanks! Actually I’m a law school graduate - so no artistic tendencies here…:wink: What made 3D my hobby is mainly the technical aspects, the problem solving, the constant need to learn new things. And in doing so you catch a thing or two about lighting. Normally I would just have slapped a HDRI of a studio lighting setup onto the environment, but since I wanted to share the scene and stay compact with the file size I had to place the lights manually.