Cleanly fade 2d transparency on 3d objects Cinema 4d and V-Ray

[krzysztof_malec]

Hi,
Sorry for starting a new topic and I haven't closed old topics yet. Too much work.
I have another problem. I want to smoothly fade the object in the animation, without showing the internal structure - analogy to 2D fade. In Cinema 4D, in the native renderer it is possible. E.J. Hassenfratz showed it nicely in the tutorial, unfortunately the video has been removed from Vimeo. I wrote to him and got help immediately. He is a very nice man with great knowledge and empathy. I am attaching two 3D scenes. One of them is a way to fade objects in native Ciniema - this is the effect I want to achieve in V-Ray. The second is the V-Ray scene and unfortunately when the objects fade out you can see their backs. I work with CAD models (STEP import). These are often design assemblies. And the disappearance of such models composed of a large number of submodels during animation looks tragic. Does V-Ray allow for such an effect that can be achieved in the native Cinema 4D renderer?
Best,
Krzysztof

[deyan.hadzhiev]

Hi krzysztof_malec, yes this effect is achievable with V-Ray, by using the MultiSubTex combined with a SamplerInfo texture as ID generator. I'm attaching your sample scene modified with this setup (also seen in the image). The scene and example I give are with nodes, because they are better for understanding how this works, but this may be achieved with classic shaders too.

Just to give a bit more explanation on the setup of the MultiSubTex
1. You need the Mode as ID Generator Texture, because the transparency level is provided by the Sampler Info node.
2. The first (and only) sub-texture must have an ID of 0, to only affect the first transparency level. Then you can have the user color texture as input to the sub-texture.
3. The Default value needs to be black, in order for all other levels to be fully transparent.


Unfortunately, this setup is not currently supported with V-Ray GPU and will only work with standard V-Ray. I will check if this can be supported on the GPU in the future, but it may take some time.

[deyan.hadzhiev]

Hi krzysztof_malec, yes this effect is achievable with V-Ray, by using the MultiSubTex combined with a SamplerInfo texture as ID generator. I'm attaching your sample scene modified with this setup (also seen in the image). The scene and example I give are with nodes, because they are better for understanding how this works, but this may be achieved with classic shaders too.

Just to give a bit more explanation on the setup of the MultiSubTex
1. You need the Mode as ID Generator Texture, because the transparency level is provided by the Sampler Info node.
2. The first (and only) sub-texture must have an ID of 0, to only affect the first transparency level. Then you can have the user color texture as input to the sub-texture.
3. The Default value needs to be black, in order for all other levels to be fully transparent.


Unfortunately, this setup is not currently supported with V-Ray GPU and will only work with standard V-Ray. I will check if this can be supported on the GPU in the future, but it may take some time.

[krzysztof_malec]

Hello Deyan,
Thank you very much for your help, knowledge and work. I admire your work as Chaos developers. Unfortunately, I have Cinema 4D R20 Studio and despite native Cinema 4D node materials, I am unable to use V-Ray node materials for this version of Cinema 4D. Only from the R21 version is this possible. Also, if you can, please show this method for classic V-Ray materials. It's a bit of a shame that it's so complicated with V-Ray. In regular Cinema, all you need to do is enable the option in the TAG of the object.
Best,
Krzysztof

[deyan.hadzhiev]

Hi again, I'm attaching a version of the sample scene using classic materials and saved with R21. Unfortunately R20 is no longer officially supported so I can't save the scene with it, but I think you should be able to open the R21 scene.

It's a bit of a shame that it's so complicated with V-Ray. In regular Cinema, all you need to do is enable the option in the TAG of the object.

I agree that this effect is more complex to achieve than it ought to be and we may consider improving such workflow in the future.

[super gnu]

this is the first time ive heard of a method to do 2d transparency effects in vray.. maybe i missed it being discussed previously.. does the same technique work in 3dsmax?

[deyan.hadzhiev]

does the same technique work in 3dsmax?

I am not a V-Ray for 3dsMax expert, but I think this approach is not directly translatable there, because the MultiSubTex implementation there does not have an ID generator input. Also keep in mind that this is not supported on GPU, which would also apply to V-Ray for 3dsMax, even if the input was available (as it is in V-Ray for Maya).

[super gnu]

i shall ask on the max forums

[deyan.hadzhiev]

super gnu - technically, if you need this effect only for the first transparency level, you don't need the ID generator input of the MultiSubTex node, as you can achieve the transparency value by simple float operations. You simply need to achieve the following expression: 1.0 - ([transparency_level] + [transparency])

Here is an example of the setup in V-Ray for Cinema 4D, and it should be replicable in V-Ray for 3dsMax:



A bit of additional explanation:
1. The invert node is necessary to actually have the opacity source, because using the expression above uses transparency.
2. The MultiSubTex in this example is only for the diffuse and is generally irrelevant.

Please do note that using the MultiSubTex approach (from previous posts) has the advantage of selecting an arbitrary transparency level (not only the first) by simply changing the ID of the sub-texture, while this expression approach works only for the first level.
Also note that this setup is affected by invisible lights in front of the objects, as they increase the transparency level.

[deyan.hadzhiev]

Actually, there is even a simpler method, given from the simplification of the expression above:
1.0 - ([transparency_level] + [transparency]) == 1.0 - [transparency_level] - [transparency] == (1.0 - [transparency]) - [transparency_level] == [opacity] - [transparency_level]

So effectively this is the setup where the Float A input is the actual opacity that will be used for the first level:

[super gnu]

Thanks for your support (certainly more timely and enthusiastic than that on the max side!) however unfortunately, according to this:

https://forums.chaos.com/forum/v-ray...parency-effect

unlike C4D and Maya, the 3dsmax samplerinfo texture does not provide transparency levels as an output.

yay!