2.8 Cycles transparent acrylic material not transparent

Hi,
I’m trying to make a tinted transparent acrylic material for a pencil sharpener basket in 2.8. I’m a relative newbie, and this is my first project in 2.8. I’ve tried following a couple of 2.79 tutorials that suggest mixing a principled shader (with high transmission value) with either a glass or transparent shader, but I keep getting a result that looks more reflective than transparent. Is this because of some 2.8 setting, or am I approaching this the wrong way?

Thanks.

1 Like

It does not look like cycles. You are sure you are not running Eevee or workbench?
Also, the transparent color node should be white, not brown.
In fact… the shader you are showing does not look like the image at all. The image have a metal structure where you point, but you use none in your principled… so are you really using that material on that place? Please check again so you really have selected the correct material.
As a note, you can never mix metal and transmission. It will not be transparent then.

If it’s EEVEE you have to make changes in two places. You have to enable Refraction in the Render tab and also turn it on in the setting of each material that needs refraction.

You don’t really have to mix a Glass shader in for something like this. Just set the Transmission, Roughness and IOR in Principled to something appropriate.

Switch to Cycles. That one looks nasty for Eevee to handle - red and table from multiple transmissive rays can’t be seen but your eyes would expect it.

Share a reference and possibly the object itself, and someone is more likely to give it a proper shot.

I agree that the image does look like Eevee, but according to the settings it’s in Cycles. FWIW I’m using an HDRI image with a couple of area lights for highlights.

I went and changed the transparent shader to white. That helped some as you can see, but the principled shader still wants to make things reflective. Toggling on/off the metallic setting didn’t make things better.

Is your screenshot in Workbench mode? That’s basically EEVEE if so. Or is the left hand side from a render? If it’s in Workbench mode then switch to Cycles Render mode to get a better look at the material as it will render.

It’s from a render. Computer specs btw:

Macbook pro 2015
Mojave 10.4.3
Intel core i7
16gb ram
AMD Radeon R9 M370X 2048 MB
Intel Iris Pro 1536 MB

Perhaps you could share the .blend file for other people to take a look at?

I’m not really sure why you’d need to mix several shaders for something like this anyway. In my screenshot below the object on the left is using the Principled shader and the one on the right is using Glass BSDF. Both look identical, with the same IOR, transmission value and the same maps piped into roughness and normal (and in both I use a volume absorption node to give the glass a green tint).

On its own the Principled Shader should be able to handle a material like your transparent acrylic.

It does seem like that should be the case. I gave it a shot with just the principled shader, rendered to 200 samples. Here’s a dropbox link to the .blend file. Sorry, as a new user I can’t attach the file directly.

The image files weren’t packed in the blend so I had to either remove some or replace some (like another HDRI) to see what was going on. A couple of things I noticed straight away that might not be helping: The scale is way off. The pencil is over 7 meters long. The acrylic tray being broken into so many separate objects is unusual too. Scale can have an impact on transmissive materials I think.

I roughly modelled a vaguely similar shape rather than trying to join all the wee objects into one. By dramatically lightening the Base Color and reducing the Roughness things started to look a little better.

I suspect combining the pullout tray into one object might help too. It gives Blender a better idea of what’s going on it terms of transmission.

The main problem here is that the Basket objects have their normals flipped.
Fix that, and the reflection will look ok.

Transmission shaders need their normals to be pointing out. If not, Cycles (and plenty other renders) will assume that the camera is inside glass/water/plastic and that the object is made of air.

1 Like

Use Overlay/Face Orientation is a very efficient way to check normals:

Generally speaking, everything should be blue. There are cases when you want red, but then you should also know how to tackle issues that can arise from it.

Make a single plane and preview the fresnel node on it. Notice how different each side looks. That’s the effect that is calculated, like Secrop describes above.

1 Like

Ah, got it. Thanks for the help, I thought that I had flipped the normals the right way, but didn’t know that there was a tool that made checking it easy.