Transparent Material with Hidden Backfaces

[Byteman3D]

https://www.shutterstock.com/video/clip-5362736-medical-animation-tennis-player--visible-skeletons

I'm working on a medical animation and trying to create the body material used in the above video. 
Some opacity with sort of Fresnel Falloff used in Self Illumination does the trick to some extent but backfaces whose front sides are looking at the camera are also visible. In the video, the effect is like the Hidden Line Viewport Shading mode. The lef at the back is not visible at all. What could be a simple approach to such material.

Thanks in advace.

 

[GeorgeK]

I am guessing you need something like this (screenshots). Just keep your outline self-illumination falloff and use a white mask along with a CoronaFrontBack, where front will be the outline falloff and back your white mask negating opacity.

(EDIT: it hides the bone so I guess won't help you directly. :( )

[Byteman3D]

I need something more like the Hide command in AutoCad, or the Hidden Line viewport shading type. (With the nice Falloff) On most of my attempts, front faces of the behing faces are also visible, crowding the image.

Still looking for ideas.

Edit : By the way, Front Back Map confuses me a lot. It doesn't seem to be working. If I assign black to Opacity, it works as expected. A Falloff map works as expected. When I assign Front/Back Map, as any of its colors black and the other white, I don't think the effect is as expected. There is no transparancy at all. I was having problems in a simple tube a few days ago. I just wanted the front face to be invisible but backface visible. Interior was always black like casting shadows.

[romullus]

You can adjust falloff so that front faces would be as transparent as you want.

[Byteman3D]

You can adjust falloff so that front faces would be as transparent as you want.

Falloff all alone does not help. Let's say, when the arm is behind the body it should be hidden, but with any transparency effect, either its front or the back faces are visible causing irregular shapes.

I have achieved the perfect hide effect with 3dsmax's Front Back Material with a transparent material with falloff in opacity in the front and shadow catcher on the back material. Unfortunately internal organs are totally invisible also.

Is there an Occlusion Exclusion for Shadow Catcher?

[romullus]

Ah, now i see what you're after. I think it could be that in the reference video, skin and bones were rendered separately and then composed together. Do you think this could work for you?

[Byteman3D]

It might work for sure, but that's the kind of workflow I'm not very fond of, and not used to very much. I wish to see the effect instantly and if any change is requested, this way it requires at least 2 renders everytime.

[GeorgeK]

Edit : By the way, Front Back Map confuses me a lot. It doesn't seem to be working. If I assign black to Opacity, it works as expected. A Falloff map works as expected. When I assign Front/Back Map, as any of its colors black and the other white, I don't think the effect is as expected. There is no transparancy at all. I was having problems in a simple tube a few days ago. I just wanted the front face to be invisible but backface visible. Interior was always black like casting shadows.

Make sure your normals are not inverted! because if the are the front back map works in reverse. Also the falloff map is properly setup with light color on edge and dark-black mask on center.

[Byteman3D]

I need urgent help on one other thing:

I have my body setup with 3dsmax Double Sided Material. Back side is a Shadow Catcher Material and Front side is a transparent material with Falloff. Image seems perfect.

The Internal organs are casting shadows on the Shadow Catcher assigned back faces. If I disable Shadow casting of internal organs, it works, but I need the shadows of that object on itself. (Intestines need shadows)
The only solution is to disable the shadow receiving of the Shadow Catching body. It doesn't seem to help. Shadow Catcher settings like Shadow Amount doesn't seem to help.

Not exactly sure but I presume it might be because of the HDR Map illuminating the scene.

[GeorgeK]

I need urgent help on one other thing:

I have my body setup with 3dsmax Double Sided Material. Back side is a Shadow Catcher Material and Front side is a transparent material with Falloff. Image seems perfect.

The Internal organs are casting shadows on the Shadow Catcher assigned back faces. If I disable Shadow casting of internal organs, it works, but I need the shadows of that object on itself. (Intestines need shadows)
The only solution is to disable the shadow receiving of the Shadow Catching body. It doesn't seem to help. Shadow Catcher settings like Shadow Amount doesn't seem to help.

Not exactly sure but I presume it might be because of the HDR Map illuminating the scene.

Can you please show us a picture of this? You might need to use RayswitchMtl for this.

[maru]

I don't want to sound rude or anything, I am just genuinely interested if there is any reason you are using Corona in this project.
As we know, Corona is intended for photorealism targeting mainly (although not only) the archviz industry.

Doing stylized/non-realistic renders like in this thread is basically a use case we did not keep in mind when designing Corona. I also do not see much benefit of using Corona here, since there are no things like global illumination, light emission, etc in the provided reference.

What I am basically trying to say is - wouldn't it be more practical (easier and faster) to use Scanline here?

[Byteman3D]

What I am basically trying to say is - wouldn't it be more practical (easier and faster) to use Scanline here?

It is sometimes, but on transparent materials and raytracing applications it is way more slow and impractical. That's why I don't use scanline that much.

I couldn't reproduce the case again to send image, by the way. Could it be possible that I was testing with interactive rendering and it isn't updated on certain changes?

[GeorgeK]

What I am basically trying to say is - wouldn't it be more practical (easier and faster) to use Scanline here?

It is sometimes, but on transparent materials and raytracing applications it is way more slow and impractical. That's why I don't use scanline that much.

I couldn't reproduce the case again to send image, by the way. Could it be possible that I was testing with interactive rendering and it isn't updated on certain changes?

No I really doubt that's the case, I will look into recreating what you are asking to help you further, please be posted!