Acrylic plastic

Hi. I am trying to achieve a realistic render of a furniture project I am doing for myself.

I really tried to research before coming to ask here. The subject seems to be overly explained…but I spend two hours looking for tips and answers…and only few things there. Every time I went into a post with the title of “transparent plastic” they were not exactly regular ones or cycles, but eevee and some kind of twist on the regular transparent plastic.

I found this super nice talk on glass by Vilem Duha at the Blender conference.

I tried two of the approaches Vilem proposes in the video, but I am not totally sure glass and acrylic plastic behaves similarly or should have different nodes. I am thinking this cause both of the approaches I tried by Vilem did not give me the 100% desired result. So it might have to do that either acrylic is not the same or that I am not experienced in physics and actually it looks like it will look in reality and I am expecting something I shouldn’t.

This is the best attempt so far. I checked at home some transparent plastics I have in the kitchen…and they do not seem to have such drastic banded refraction, you can see how the wood behind the transparent plastic gets distorted. The plastic is 2mm thick…and in the render looks like if it was solid glass…my attempt is closer to a “case” of the phone if you make a section…more like a 2 mm skin.

I also notice the bottom edge does not show the thickness of the plastic (which helps to think it looks like a solid block of glass) …and the little bit a can see is a really dark line, which I am trying to avoid.

This is the node I copied from the video:

You can also see the plastic mesh is using a solidify modifier. But I checked applying everything and the outcome is the same…so I don’t think the use of modifiers is a problem.

I feel I am not far, but somehow it does not look as I am trying to build the furniture…maybe somone here with much more experience than me can help me to understand the principles behind the transparent plastic and share some tips.

Thank you

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I guess, if you increase the glossy bounces like in the video,this makes mostly sence,if you have a volumectric mesh like a bottle ect. Where the chance that a sample reflection hits the “dark” spots are higher,vs if you only have a flat glass plate.

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Hi! thanks. I am not sure I got it, I am guessing that acrylic and glass behave similar?

Sure,Acrylic glass is like glass,has a IOR iirc of 1.49 .glass is in the same range.Its just the amount of reflection,no rocket science.

No it is not, that is the reason why I am in the Material category of a forum and not asking to a rocket engineer.

I just saying,the reflection calculation Blender uses is basicly the Fresnel equation in the glass shader,the IOR input ect.

Here you can get IOR values of most common materials

Here are PMMA acrylic-plastic

Thank you so much! Dont you think the plastic in the render looks far from good ? I am interested in your opinion and also to know if there is a way to make it look like a thickened surfaces and not a glass blocl .

Do you think is just the IOR? If it is not a problem I would like to ask you if you could check the node setup I posted. Hope its not a problem, I am trying to learn how to achieve the material . I want to present it in a contest and I am trying to show it is a skin of plastic and not a solid glass.

Thank you ! If you do not have time its ok too :slight_smile:

To me it looks decent.The most shading problems with glass are, if the mesh (especially the edges) are not subdived enough or uneven,and if the normals are not weighted correctly.

I still can not see the thickness of the plastic…

In some instances you really just won’t see the thickness of the acrylic. That is partially because a) in my experience cycles just is funny with it’s IOR. I know there are going to be a pile of people on top of me now saying BUT THE MATH IS RIGHT! Be that as it may, compare it to other engines, something just feels wrong about how it bends light sometimes and I have just learned to work around that as best I can and save my complaints for case studies; b) improper beveling of the edge of the solidify is preventing it from reflecting light internally in a way that makes the edge visible; c) angle of view is making the edges hard to see; d) in real life once acrylic is bent and cut off it is typically sanded to a “smooth” finish at the edge but still leaves micro striations that give it a slight amount of anisotropy which tell us visually there is an edge there.

There are other things too to add to the realism. meshes coming in contact with transmissive surfaces should intersect the glass just slightly, a volume is meneficial to darken deep parts of the acrylic, and I think lastly, while this doesn’t have a huge effect on non-contact transmissive surfaces, 2mm is really thin, and even in respect to camera size, acrylic that thin just wouldn’t be used for the application you are using it for and that might hurt the realism as well.

Making something completely photo real is less of an art of changing node settings and more a story telling art about how the model or material came to be in the first place. Obviously you cant do EVERYthing and probably shouldnt do everything the same way as in real life, but the story of point a to point b driving your decision making will help with realism a lot. who made it, how did they make it, was there damage in instalation, is it new or did someone touch it, etc.

Thank you for such a detailed response.

Regarding point B: Are you affirming this or its more like a rule of thumb ? I just want to understand if there is something wrong in my model or you are just enumerating what to check.

Point D: I will add the bevels there…maybe its better to get rid of all the modifiers and just model the shape.

I will also make the wood to intersect the acrylic if that helps. I spend so much time exactly doing the opposite…:frowning:

Thanks I did not know I should make the things intersect with the acrylic surface.

d isnt really about bevels it is more of an anisotropy shader issue. I would add a different material to the edge where the acrylic would be cut with anisotropic roughness on the glass and if you havve a bump map with striations, maybe that too. If not, skip the bump map. On point B, that is more of a rule of thumb. I am not looking at your wire so IDK for sure what is going on but given that I don’t see a little white line refracted sorta behind the glass I am suspecting either you don’t have a strong bevel, OR, your lighting is the problem. One or the other. But, in the grand scheme of things, 90 degree angles dont show up well in refracted glass if both halves are in shade. Its like metal. And edge might be sharp but if you give it just a SLIIIIIGHT bevel it will get a little glare on the edge and make it look more real.

In terms of the intersection, it is mixed schools of thought. One argument is nothing ever truly touches and it wouldn’t happen like that, the other is, and this is my preferred thought process, if you place a squishy ball against glass and it makes good contact youll notice the refracted image begin to separate from the object in the transmission. Neither way is really 100% right or wrong except with fluids where the latter is 100% the correct way in most PBR engines, regarding 2 mesh fluids. But with solids I tend to see more realistic results by intersecting the mesh JUST slightly, I mean, a hair, not even if it is a close up, half a hair.

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I am getting closer. I will redo the mesh for the acrylic without modifiers and intersecting the wood.
I hope I can keep posting so I get some feedback from you!

Absolutely. Let me know. If you havn’t applied the modifiers you can probably do it with all modifiers if you want but that is really just personal preference. I gave it a shot and was able to do it with all modifiers so really just up to you in the end.

If its possible to do it with modifiers even better. I am using modifiers so I can change radius and thickness of the surface for example…if I change my mind.

I realized the last render I posted its not entirely accurate. The shadows (floor) do not show the acrylic surface. I imagine the shadow should have at least a boundary made by the outer edges of the acrylic ?

It would be easier to provide ideas if we had a file to look at. Textures (not hdr) included, and modifiers not applied. I’m not gonna spend time building a model, coming up with ideas that don’t apply to your case because you did it differently. I have less important things to waste my time on :smiley:

I’m stealing that little bit at the end there LOL

Good morning ! How did you sleep today?
I will happily share the model when I get home. In the meantime I would like to ask you something I am sure you would be able to help me:

If you check the last render I posted you will see that I turned off the shadows in the acrylic. The reason for this is to improve the light in the wood structure below the acrylic. Without doing this I was getting a super dark structure. But It has a cost…I lost the perimeter of the acrylic shadow cast on the floor. In the render you can appreciate I only have the shadow of the wood structure.
Here is my node:

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Here with the acrylic filtering the shadows:

Here with the acrylic not using the light pass node (meaning shadows active)


I am a bit confused about how this should look if it was actually standing in a room of the house.
On one side the acrylic with no shadows shows much better the structure and the lighting seems to be more appealing…but somehow not sure if it looks a bit artificial…almost like the acrylic is not there.
On the other hand the acrylic casting shadows (how it should be in real life?) does not show any detail. On the shadow cast on the floor…we can just see a big chunk of shadow without any detail. On top of that the wood structure looks extremely dark.

I am trying to achieve something closer to what it would look in reality? Again do not get annoyed…I am just using this term cause I am not sure how to refer to: I would like to achieve a " believable render " .

I imagine I should be able to see the shadow details like the first image, but also see the borders of the acrylic in the floor. Now looks like there is no acrylic surface at all. The second one seems to not be realistic either. I am also aware I should have caustics…but I know I can not achieve that with cycles…and I am too new to try with luxcore.

Please find also attached the table top if it helps.

Acrylic_Forum.blend (855.4 KB)
Thank you

A quick try,with the ray depth multiply you can control how much shadow should appear.1 is no shadow and lower gets more shadow.
I have placed a plane with 0.18 diffuse underneath the acryl object, to get a more realistic light behavior with shadows we can see.