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Translucent materials with GI(Should I just go with Maya?)

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Ihab Ali
Translucent materials with GI(Should I just go with Maya?)
on Jan 4, 2015 at 4:50:00 pm

Hello All,
I'm in the process of evaluating either upgrading to C4D Studio or purchasing Maya 2015(currently using C4D Lite and studio trial versions as well as Maya Student edition).

One thing I'm completely unable to figure out after a lot of research is how to create translucent materials in C4D where light (including luminance from objects and GI lights) can shine though and pass that light onto other surfaces as well. I know of the backlight shader but that doesn't pass GI lighting on the other side and while SSS reacts to GI it does not pass on illumination data onto the other side of the material(i.e. if I have a light source on one side of a object with SSS and there is an object on the opposite side, that object gets no illumination through the SSS object). I also know that Vray for C4D makes it possible to use 2sided shaders but that's an additional renderer that needs to be purchased and it seems from my limited knowledge of Maya that this is possible through the translucency channel with standard and Mental Ray materials out of the box.

I love the simplicity of the C4D UI and general structure, but for almost 4K USD, Maya is starting to sound like a better alternative especially that it comes with Mental Ray and whole bunch of advanced fluid simulation capabilities. And it is simple things like the ability to create something as simple as translucent materials natively in C4D that are making me think that Maya is a more cost effective package.


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Adam Trachtenberg
Re: Translucent materials with GI(Should I just go with Maya?)
on Jan 4, 2015 at 5:24:25 pm

Cinema's native (physical) renderer will transmit GI light through transparent and translucent materials. Is there a specific effect you're trying to achieve?


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Ihab Ali
Re: Translucent materials with GI(Should I just go with Maya?)
on Jan 4, 2015 at 6:06:33 pm

Hi Adam,
Thanks for the quick reply. My initial problem was trying to setup a translucent texture for sheets of paper in a dynamics simulation I created to composite back into live action footage. The only way I could achieve the effect of light shining though paper(illuminating the paper with the color of the actual light as well as have shadows visible on the darker side of the paper) was through the backlight shader. This works fine but in order for it to work I have to have real lights in the scene. I try to do as much as possible through GI image based lighting(from HDR probes) and only use additional lights to achieve a specific effect on the objects that are to be composited.

Then I thought I'd try and create the effect of lamp shade lit from the inside using a sphere or a cylinder with a luminance channel on its material. Again backlight shader works but only if I put a real light inside that lamp shade model....and the problem with lights in C4D is that they don't have shapes, so I wouldn't be able to see anything except a sphere of light shinning through the lamp shade.

Furthermore with the backlight shader, if there is a bounce from an object of a specific color on the other side of the backlit material, that bounce does not appear(e.g. I have a bright red object very close to the surface of a paper so you'd be able to see a slight red cast on the other side of the paper in addition to the shadows..etc)


Now all this is solved with the SSS shader which does react to GI and objects luminance channels(so in my previous example of the red object it actually passes the bounce to the other side) and obviously SSS can properly simulate translucency. But I tried the lamp shade example with a SSS material and while the shade is illuminated it doesn't seem to cast any lights on anything else in the scene. Also and maybe I just couldn't tweak the shader well but I couldn't seem to get the shape of the light object to shine through the lamp shade.

Now I know it is easy to fake all of these effects in many ways including mixing channels to generate both the translucency effect as well as the luminance but it just doesn't sound like this could produce photo realistic results with the same ease as the shaders that I was playing with in Maya.

Again I'm new to both platforms so I'm just trying to determine if my observations are correct. Ultimately I would choose the platform that allows me to produce the most photo realistic renders with the most ease(although so far both requirements don't seem to be achievable at the same time from what I saw with C4D and Maya).


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Ihab Ali
Re: Translucent materials with GI(Should I just go with Maya?)
on Jan 4, 2015 at 6:15:37 pm

Oh and sorry forgot to mention, I'm using the physical renderer in C4D for all my experiments.


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Adam Trachtenberg
Re: Translucent materials with GI(Should I just go with Maya?)
on Jan 5, 2015 at 5:00:04 am

SSS will transmit GI light, but it only seems to work with the Quasi Monte Carlo GI method. All in all it would be dreadfully slow if you want to get a clean result. I'm not familiar with the MR shader you used but if it works, and this is something you do all the time, that may be the way to go.

I just had a play with Octane Render in Cinema and it does a nice job surprisingly quickly, but that's another cost and it requires at least one decent NVidia card.


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Ihab Ali
Re: Translucent materials with GI(Should I just go with Maya?)
on Jan 5, 2015 at 5:34:06 am

I just tried my test scene with QMC and I see your point about getting decent results. In addition, it seems I was wrong about SSS, it seems to only illuminate the full surface of the object as opposed to show the shape of the light source. Obviously this is not a deal breaker of me but I would really like to know how this can be handled properly in C4D, there doesn't seem to be much documentation out there on translucency and it seems like a very basic that that C4D should be able to do and do well.

Do you have any other advise on how this effect can be achieved in C4D(I'm talking about light behind paper, lamp shade...etc)? I've seen people fake this with a ramp type shader and it looks ok just not photorealistic.


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