Problems with different kinds of reflections

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Old 05 May 2013   #1
Problems with different kinds of reflections

Hello, i'm doing my bachelors degree project with which i encountered a problem. I am using Mental ray, and when i apply a standart material with raytrace reflections i get really neat reflections but some distortions in the bottom. When i use an architecture material like a mirror or someting reflective i dont get the distortions but the reflections are not as nice. Any ideas how to fix the raytrace problems or to achieve the same reflections via other means? Thanks in advice

this one is on standart with raytrace reflections


this one is an arhicetural material - mirror


this is the wireframe. the thing i notice is the reflections are distorted by the poligons. as if it is not smooth but it is. and when i add more smoothness it's still distorted


another question i have: the object is a scaled sphere and then i split it in 3 parts by detaching the mesh. I never moved any part of the object and in the render the boundaries of the objects can be seen. is there a way to avoid that? to look smooth without interuptions?

Last edited by Devailo1 : 05 May 2013 at 08:08 PM.
 
Old 05 May 2013   #2
Unless you really need to use a standard material I would just use the MR material

If you want to fix the seam where you separated the mesh, before separating the mesh, apply the Edit Normals modifier, and then select all of the normals and click Make Explicit
That will basically force the normals to always remain the same.
However, you can't simply detach parts of the mesh, otherwise it will ruin the normals. Instead, select the part you want to break off, then make a copy of the whole object, delete the selection from the original and then go to the copy and invert your selection and delete. You can delete polygons just fine, but you can't detach them, so that's a way to get around it.
After that, since the normals are explicit they won't change.
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Old 05 May 2013   #3
Originally Posted by darthviper107: *Trick to split objects but without Normal seam*


Awesome, never thought of that and never used Make Explicit before.
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Old 05 May 2013   #4
You can also do a normal map from your smooth surface, but this is a better solution. Had to use it to do some game stuff where objects were getting split but needed to look like whole objects
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Old 05 May 2013   #5
i really did not understand what i did with those normals but it worked thanks for that. Now about the reflection. It doesnt really matter which reflection i use i just want to have the effect of the standart raytrace reflection, becouse the other one just doesnt look that good

what i mean is not the quallity, but the effect. In the standart version the reflected mountains look really far and bent as for the mental ray reflections, they look closer and normal-er how can i do that far bent effect with a mental ray material?

Last edited by Devailo1 : 05 May 2013 at 09:13 PM.
 
Old 05 May 2013   #6
Assuming nothing has changed in the scene between the two, my guess would be that the "Mirror" preset has some small degree of Anistropy applied - this is the effect you get on, for example, the underside of CDs and on galvanized alluminium, where reflections are distorted (sometimes a little, sometimes hugely so that they're little more than a flat line). Try making an Arch and Design material, but don't load a preset - instead, just make sure the reflection value is set to 100 and the colour is white - see how it looks then. If they look too distorted (like the "Mirror" preset" then perhaps it's the raytrace map which has the anistropy - eitherway, try playing with the anistropy parameters in the Arch&Design material.
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Old 05 May 2013   #7
Originally Posted by DanGrover: Assuming nothing has changed in the scene between the two, my guess would be that the "Mirror" preset has some small degree of Anistropy applied - this is the effect you get on, for example, the underside of CDs and on galvanized alluminium, where reflections are distorted (sometimes a little, sometimes hugely so that they're little more than a flat line). Try making an Arch and Design material, but don't load a preset - instead, just make sure the reflection value is set to 100 and the colour is white - see how it looks then. If they look too distorted (like the "Mirror" preset" then perhaps it's the raytrace map which has the anistropy - eitherway, try playing with the anistropy parameters in the Arch&Design material.


i tried it but anistrophy changes just how the object is highlighted, not the way it reflects the environment.
another interesting fact is that in the material editor - the material spheres with the background colors - both look the same but in the scene when rendering are completely different.


fullsize picture

in the render the left one is the standart raytrace material and the right one is the arch&design
i want to have the distant reflections like in the standart raytrace but to avoid those artefacts on top and bottom of the left object.

edit: when i use a raytrace material instead of a standart material with raytrace for reflections, i get the same results like with arch & design - the close reflections. i've been experimenting with lots of things and i always get the same reflectoins and cannot achieve the distant reflections achieved by the standart material and a raytrace reflection.

edit 2: ok this is really weird. when i apply the 2 different types of reflection to spheres they get the same result


so the problem seems to come from the mode. the capsule is a scaled sphere. when i try a sphere with more segments and then scale it and apply the raytrace reflections, the problems still occur. I am really baffled now.

Last edited by Devailo1 : 05 May 2013 at 03:05 PM.
 
Old 05 May 2013   #8
Perhaps you need to reset Xform on the sphere after scaling it
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Old 05 May 2013   #9
Originally Posted by darthviper107: Perhaps you need to reset Xform on the sphere after scaling it


it almost worked...when i reset the xform the reflection was just like i wanted it(with all kinds of mental ray materials), but again the faces on top and bottom could be told apart as if it was faceted. i dont think its about the smoothing because in the middle the problem does not occur and all 3 parts are from the same object with the same settings and smoothings.I have no idea whats wrong.

when i turned on realistic shading in the viewport the problem can be seen.
weird thing is the 2 object reacted differently on the reset xform.

Last edited by Devailo1 : 05 May 2013 at 06:22 PM.
 
Old 05 May 2013   #10
Reset Xform probably resets the normals
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Old 05 May 2013   #11
well i dont know what to do anymore..i will have to change the idea..i really dont understand why this is happening.

edit: i believe i tried everything. i modeled the capsule just to avoid the scaling of a sphere and there were no distortions but the reflections were the "close distance" type with all kind of materials. so the other one "far distance" reflection might be a bug. If there was only a way to control how things were reflected..

Last edited by Devailo1 : 05 May 2013 at 11:42 PM.
 
Old 05 May 2013   #12
I tried replicating your problem, but couldn't. Left one is a standard material with raytrace, right one is A&D. Top image - mrSky and geometry, bottom image - IBL with hdri.

http://img407.imageshack.us/img407/1935/testrefl.jpg
 
Old 05 May 2013   #13
i did a test by checking how the reflections react by the scaling in a short animation(its too short so im gonna show you 4 pics of it)

it seems that the reflections map scale with the object in the case of the arch & design or other more advanced maps. as the standart raytrace refletion doesn't scale but it gets the edges on top and bottom.






is there a way to reset the maps or someting? still when i tried it with modeling the capsule instead of scaling a sphere the refletions were again scaled.
 
Old 05 May 2013   #14
I've loosely followed this thread and I might not get what the problem is but since you can't get rid of it try the following:

select the object with the weird reflections/normals, go to the utility tab, choose 'more', then 'channel info', then click on the 'channel info' button. In the window that now comes up, there'll be several entries, right click on the last one and choose 'clear'. Render. If it didn't help, clear the last entry again and render.
Please report here if it helped, I'd be interested to see if that was the problem.

Sometimes, when I import obj files I get similar normal problems that are persistent and cannot be deleted with the edit normals modifier, this is the only working method to get rid of them.
 
Old 05 May 2013   #15
tried it and nothing changed.

i tried a desperate method but failed. i tried blending the 2 kinds of reflections becouse the one is perfect in the middle and the other one on the ends. But i couldnt. Here is a peculiar thing though. Looking exaclty the same in the material editor but when put together, they look different.

 
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