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Alpha Channel problem
Posted: 22 December 2019 04:51 PM   [ Ignore ]  
Total Posts:  39
Joined  2019-11-25

I finally connected the wing to the engine, after hours of work:-)

But now the alpha channel is giving me some problems.
As you can see in my file, i made a gradient in the material channel, and an alpha channel for the windows of my plane.
But when i render the plane, it seems not good.

The edges are not tight at all, the same for the edges of my gradiënt.

Is there a problem with my light? I want to have the airplane in the air, with clouds, but do i have to change the settings of my light to get the alpha channel better?

I don’t know what is going wrong.

thanks,

 

https://www.dropbox.com/sh/8etxp0y934rcg8g/AAC-EkhqehhY9DSERbiWUU8ka?dl=0

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Posted: 22 December 2019 06:14 PM   [ Ignore ]   [ # 1 ]  
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Hi Annet,

The problem is based on several parts.  The first part is that the image size is pretty small. This is relative to the final use and camera setting, but given the mesh density, this is out of balance. If the elements in the image were seen in the rendering left to right, the maximum render resolution would be around 500 pixels. However, the low resolution showcases the underlying problem clearly.

It is essential here to understand the problem that the layer transparency causes. The effect is simply explained: The layer transparency provides only a fraction of the RGB value in the seams around the elements. Which typically sufficient while working in Photoshop. But to apply the transparency values again, it will affect the transparency twice, one time in the color channel, and again in the Alpha Channel.

In VFX, compositing this problem is typically solved in Un-multiply/Premultiply processes. Since the image here is based pretty much on path-based-elements only,  the clean edge of the path is destroyed by the low resolution and the idea of Anti Aliasing that photoshop has.

With the path based image file, do the following:

• Set the image size to 16384 pixels (Image, not canvas). (it was only 1024 wide in the provided file.)

• Select the top folder, then with option/alt key down, in the Layer Options, use Merge Visible. let go of the Alt/Option key when done

• With the Cmd/Control key down, click on that new layer.

• While the Selection is active, got to Selection> Save Selection. Then CMD+D to deselect the active ant-selection.

• Go to the Channels and select the alpha (visibility), and the visibility off for anything else.

• In Filter> Others> Minimum 3 pixels.

• Now set the Image size 8192, or leave it in that size you have. Again, the size is relative to the final use in the rendering.

• Save the image and replace it with the one in the scene file.

• Use the Alpha channel. (Use the Layer-set Select Button)

• Set the Anti Alias in Cinema 4D to Best.

It should look much better now. See image
https://www.amazon.com/clouddrive/share/bNKmbckDRREW7rCk0fVj4oyzwzYRf5Ui83FgCJekZP4

(Photoshop files must be saved in PSD/PSB compatible mode (which adds a merged layer), Cinema 4D is not rendering Path based information from Ps. If you use the Select option, please keep this in mind.)


All the best

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Dr. Sassi V. Sassmannshausen Ph.D.
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Posted: 22 December 2019 06:56 PM   [ Ignore ]   [ # 2 ]  
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P.S.:

Here is a screen capture of the process with the Path based Photoshop file.

https://www.amazon.com/clouddrive/share/PAsmLttoavYtq7XjrZc7lBHcYYktYfbWQ5zj1cdjTKy

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Dr. Sassi V. Sassmannshausen Ph.D.
Cinema 4D Mentor since 2004
Maxon Master Trainer, VES, DCS

Photography For C4D Artists: 200 Free Tutorials.
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Posted: 22 December 2019 08:12 PM   [ Ignore ]   [ # 3 ]  
Total Posts:  39
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Hello Dr. Sassi,

Thank you for fast reply.
I fixed the problem with your help:-)

But now, I stumbled accross the next issue with the same alpha channel….
When I use text in the Alpha channel then my symmetry will need a rotation on the other side of the plane.
Can i use a formula or a work around to solve this, because i need to save my symmetry.

Thanks in advance,

Annet

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Posted: 22 December 2019 09:43 PM   [ Ignore ]   [ # 4 ]  
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You’re very welcome, Annet.

Please explore these two files:
https://www.amazon.com/clouddrive/share/swhPQ8vJaOOtOxW13e7I8QAcNVESy1DKu66lV3s9gaW

Your set up was based on a flat projection. Both examples use flat accordingly.
One uses a second Alpha channel, the other one just uses a negative for the U parameter, and offset it then to reposition it.
For both cases, I have made a screenshot.

To have control of the textures, a Polygon selection was made and used in Texture Tags.
Please note that layering Materials/Texture Tags in the Object Manager works with the most right-sided as the top one.
More about this:
https://help.maxon.net/us/index.html#TTEXTURE-ID_TAGPROPERTIES

All the best

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Dr. Sassi V. Sassmannshausen Ph.D.
Cinema 4D Mentor since 2004
Maxon Master Trainer, VES, DCS

Photography For C4D Artists: 200 Free Tutorials.
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Posted: 23 December 2019 01:03 PM   [ Ignore ]   [ # 5 ]  
Total Posts:  39
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Thank you for your reply.

I explore your two files, thanks for that, but still having problems with the texturing.
In my case i made a polygon selection and used these in te Texture tag. So far so good.

I guess the symmetry is the problem. Is there a way to avoid the mirror texturing on the other side?
It took me hours to find out that I can put my texture also on the symmetrie and position it at the right place, but how can I delete the other texture? Still I see the ‘mirror’ texture from the symmetrie.
The problem can not be solved by changing the side of the protection to ‘front’. Also google and several forums did nog solve my problem..


For example I put a symmetrie in your file, and then i’ve got the same problem.

Thanks for helping me out.

https://www.dropbox.com/sh/hwwhwqitcif95dw/AAA8-Lp-qBq3ABBRNErz-zn6a?dl=0

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Posted: 23 December 2019 04:58 PM   [ Ignore ]   [ # 6 ]  
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Hi Annet,

Quite honestly, I’m not happy to even suggest this option. It is a symmetry set up, and with that comes the problem of exactly this problem. Anyway, you asked for it and is, to my knowledge, the only way to do it. To state it clearly:  THIS has huge limitations! Too many to list them, but to point out a few, it is limited to a certain polygon angle, needs a Pin Material Tag to work if any point of the object moves that has the Texture.
Furthermore, it is compared to UVW mapping just only really accurate on flat surfaces in a 90º system, or needs the pre-adjustment for the surface deformation, if possible at all. In other words, don’t use it if you can avoid it. If you run into trouble, here is my free: “I told you so!”

Like with N-Gons, the Symmetry object is excellent during the modeling process, but get rid of both when you are done modeling. Anything else is just not good advice.

With all of that being said:
https://www.amazon.com/clouddrive/share/7cf5Yru3nDNPm93KlL2azqo9RHTwAXHBZQttYdVbrCw

There are certainly more option to squeeze this out of other material systems, I stick with it: Avoid this at all cost.

Cheers

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Dr. Sassi V. Sassmannshausen Ph.D.
Cinema 4D Mentor since 2004
Maxon Master Trainer, VES, DCS

Photography For C4D Artists: 200 Free Tutorials.
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Posted: 23 December 2019 08:59 PM   [ Ignore ]   [ # 7 ]  
Total Posts:  39
Joined  2019-11-25

Thanks for the reply.
I understand its better for me to leave the symmetry at this point.

I am done modeling so i think that’s oké.

Thanks again for your help so far.

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Posted: 23 December 2019 09:21 PM   [ Ignore ]   [ # 8 ]  
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Annet,

I assume you save iterations of your files, so you can always go a step back and try alternative routes.

Let me know if there is anything else; I’m happy to look into it.

ENJOY.

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Dr. Sassi V. Sassmannshausen Ph.D.
Cinema 4D Mentor since 2004
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Photography For C4D Artists: 200 Free Tutorials.
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