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reflections going through object - steep normals

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tas3d: Member; 120 posts; Joined: Jan. 2012; Offline

Oct. 15, 2013 11:34 p.m.

Hey,

Take a look at the screengrab, here is what happens.

A Grid with Mountain SOP, then Facet to get normals. Applied material with mirror like reflections.

Behind this Grid is Torus with red material applied.

Then what happens is, normals of grid are so steep, that they reflect incident rays towards Torus, and I can see it in reflections! Im new to Mantra, is it normal ? How can I avoid such reflections. ?

Cheers!

Attachments:
snapshot6.jpeg (171.2 KB)
steepNormals.hipnc (1.5 MB)

Michal Tas Maciejewski @ www.vfxtricks.com


tmdag: Member; 168 posts; Joined:; Offline

Oct. 17, 2013 9:03 p.m.

You have to untick “Ensure Face Pointing Forward” in shader settings.

I have attached scene file explaining what is happening.

Cheers!

Attachments:
steepNormalsSolved.hipnc (1.5 MB)

Albert


Sadjad Rabiee: Member; 1391 posts; Joined: Dec. 2010; Offline

Oct. 19, 2013 5:24 a.m.

Thanks tmdag

But I have same problem and your solution not worked correctly !

Maybe this is a bug in my Houdini Version : 12.5.469 Linux

https://www.youtube.com/c/sadjadrabiee [www.youtube.com]
Rabiee.Sadjad@Gmail.Com


tas3d: Member; 120 posts; Joined: Jan. 2012; Offline

Oct. 19, 2013 5:20 p.m.

it sovled my problem, if I raise Reflection Angle to >0. thanks for that!

But the issue still exists if I apply even slightest bump map. Then I get red color all over the place.

any ideas ?

Attachments:
bump.jpg (58.3 KB)
steepNormalsBump.hipnc (1.5 MB)

Michal Tas Maciejewski @ www.vfxtricks.com


Sadjad Rabiee: Member; 1391 posts; Joined: Dec. 2010; Offline

Oct. 20, 2013 5:31 a.m.

I think turn off “Ensure Faces Point Forward” parameter is not very good idea !
Because it's just work on the front side of the grid !
If you render back side , you can see very wrong result !

Can you find another solution !? :?

https://www.youtube.com/c/sadjadrabiee [www.youtube.com]
Rabiee.Sadjad@Gmail.Com


Sadjad Rabiee: Member; 1391 posts; Joined: Dec. 2010; Offline

Oct. 20, 2013 5:36 a.m.

In my project I need to render double side correctly ,because i have a cloth simulation instead of static grid or ground !

Edited by - Oct. 20, 2013 05:41:26

https://www.youtube.com/c/sadjadrabiee [www.youtube.com]
Rabiee.Sadjad@Gmail.Com

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