2 Bugs for material with Interal medium

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butaixianran
Posts: 9
Joined: Fri Jan 02, 2015 3:58 pm

2 Bugs for material with Interal medium

Post by butaixianran » Fri Nov 09, 2018 2:47 am

When importing material from .igm/.pigm into C4d, if internal medium is used, the rendering result won't be correct in C4d.

Bug1:
Specular which checked transparent with internal medium, will be rendered in a wrong way.

Use any liquids from indigo material lib to check this problem.

For example, apple juice.
This is how it should looks like:
apple_juice.jpg
And this is how it is in c4d:
apple_juice_c4d.jpg
Bug2:
When an interal medium uses another interal medium, the second one won't be imported into c4d.

Use the Fast skin material form indigo marterial lib to check this problem.

This is how it should looks like:
skin.jpg
Its setting:
skin_internalM.jpg
skin_internalM's_internalM.jpg

This is how it is in c4d:
skin_c4d.jpg
skin_mat_c4d.jpg
skin_mat_c4d.jpg (3.62 KiB) Viewed 309 times
In C4d, the first internal medium's internal medium channel is unchecked:
skin_internalM_c4d.jpg
And in this channel, there is no data setting there.


Indigo version:
Indigo for Cinema 4D 4.2.21

I've tried several versions, all have same problems.

Tyler
Posts: 53
Joined: Thu Oct 18, 2018 12:03 pm

Re: 2 Bugs for material with Interal medium

Post by Tyler » Sat Nov 10, 2018 12:01 am

as i remember, it keeps the correct properties if you import the mat trough a new shader using "external" and your mat.

butaixianran
Posts: 9
Joined: Fri Jan 02, 2015 3:58 pm

Re: 2 Bugs for material with Interal medium

Post by butaixianran » Sat Nov 10, 2018 5:51 am

I did some further test, may find the key problem for Bug 1.

For example, in indigo, apple juice mat's internal medium uses SSS, and the gain value for absorption is 52.0702, the gain value for scattering is 4.127.

After importing this mat into C4d, the Gain value for absorption now is 5207% and gain value for scattering is 412.7%。
before turn gain value down.jpg

But, as my testing, gain value of 1.0 in indigo, does not have the same render result as gain value of 100% in C4d.

And, I found out, gain value of 1.0 in indigo actually has the same render result as gain value of 10% in C4d.


So, for this apple juice mat example, I update its gain value from 5207% and 412.7% to 520.7% and 41.27% in C4d.
after turn gain value down.jpg

Now, I have the same apple juice as it was in indigo.

Pls fix this bug, thanks.

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fused
Developer
Posts: 3554
Joined: Fri Sep 22, 2006 7:19 am
Location: Berlin, Germany
3D Software: Cinema 4D

Re: 2 Bugs for material with Interal medium

Post by fused » Tue Nov 13, 2018 4:23 am

Hi butaixianran,

I'm not sure the gain problem is a bug, but I will investigate to make sure.

Regarding the missing medium, I will make sure to fix that one.

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fused
Developer
Posts: 3554
Joined: Fri Sep 22, 2006 7:19 am
Location: Berlin, Germany
3D Software: Cinema 4D

Re: 2 Bugs for material with Interal medium

Post by fused » Wed Nov 14, 2018 12:25 am

Ok I looked into this.

Bug 1:

What you describe is not actually a bug, but is something related to scale. A gain of 5207% corresponds to 52.0702. The imported values for the absorption spectrum and the values then passed to the renderer are correct.

However, I did find a bug related to the scattering rgb spectrum where the values passed to the renderer were not inversed when they should have been - I fixed that.

Absorption depeneds on the distance traveled through the medium, so scale matters. The reason the juice material (and other materials) dont show up properly in the preview is to do with the scale of the preview scenes. I'm adding a "preview scale" option to to the "extra options" in the material.

Bug 2:

The issue here was that the diffuse transmitter material types medium was not imported. Fixed that as well.

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