Bizarre grain

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Old 06 June 2013   #16
if you could replace the geo with simpler cylinders or something so we could look at it maybe we' could see whats going on. Obviously not the hdri, you say it's doing it with other maps anyways right.
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Old 06 June 2013   #17
Originally Posted by LucentDreams: if you could replace the geo with simpler cylinders or something so we could look at it maybe we' could see whats going on. Obviously not the hdri, you say it's doing it with other maps anyways right.


Yeah, I'll do that tomorrow. It would be strange if it had something to do with this geometry.
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Old 06 June 2013   #18
Could possibly be a funky normal tag?
Were the gears imported form a CAD app?
 
Old 06 June 2013   #19
When a surface is curved, the curvature causes that part of the object to receive light and reflections from a large portion of the surrounding image. When a surface is flat, it is picking out a very small part of the sky object to base its illumination off of, this is likely what is causing your grain imho.

Seeing as the entire object is the same blurred metal texture though, you can potentially save a helluva lot of render time in this animation. Now this will depend on what else might have to happen in the project, but if it were me...:

Disable GI / indirect illumination, its adding very little to the scene. On that object, 80% of what youre looking at is just reflections on the surface, throw in a pair of large area lights and its going to make very little difference to the visual image but will save you a ton of render time.

Next, open your hdri in photoshop and blur the living crap out of it, and save it as a new version. Instead of using blurred reflections in the render engine (sloooooooooooow) just pre-blur the reflective image and use that as the sky (faaaaaast) Use a second crisp copy of the image as the background in the render.

Thirdly, this model would take post-DOF very nicely. Just add a depth map and blur it in photoshop/AE afterwards.

If you do the first two, your render times will plummet, if you do the third too, your render time will probably be 1/100th of the original, and youll be grain-free.
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Old 06 June 2013   #20
Why do you use GI when you're objects seem to be 100% reflective?
GI contributes to the diffuse component of a surface,
the reflective one is untouched.
 
Old 06 June 2013   #21
First of all sorry about the Indirect Illumination thing, i did not realize that you were referring to the Physical Renderer sub group with that, but now it is making perfect sense.

Originally Posted by typografschaft: Why do you use GI when you're objects seem to be 100% reflective? GI contributes to the diffuse component of a surface, the reflective one is untouched.


At least the standard gi engine does. It does produce reflective/refractive caustics without the raytracing caustic engine. I am not sure about the physical renderer though.

Have you enabled GI-Area Light for the HDRI material ? If so, increase your shadow subdivisions to at least 2 (or turn it off, as there is almost no shadow contribution in your image). The last screenshot without DOF also suggests that blurry sampling is having troubles to unify the incoming reflection rays (distant flat areas and areas facing other objects). Have you tried to increase the blurriness subdivisions by the factor 1.5 to 2.0 ?
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Old 06 June 2013   #22
Originally Posted by Troyan: Here it is with no DOF. Same issue. Setting the blurry reflection samples higher does help reduce the grain, but again, why would there be absolutely no grain at all on some parts and silly amount of grain on others? Same texture, reflecting the same environment, same everything. Shouldn't there be uniform grain across everything, especially surfaces that are right next to each other?


The angle of incidence is responsible for reflections seen. Hence, rotating the hdri will change
that angle and the reflections on the surfaces.

How are you mapping the material ... uvw, spherical, frontal ? On the sample attached, the
cube on the right is tiled at 25% to minimize any aberrations. The other primitives are 100%
and mapping set to cubic. Simple noise is in the bump channel.

If I were troubleshooting this, I'd dupe the texture and apply it to any flat surface geom,
less any fx like reflection, etc. That should give you no grain at all. Last, for a model like
this I'd pull the default options of ray depth, reflection and shadow back to 6-5-6 rather than
15-5-15

As mentioned, a stripped down scene would help identify other options.

Edit:
Image without bump 5% blurry reflections
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Last edited by vid2k2 : 06 June 2013 at 02:08 PM.
 
Old 06 June 2013   #23
Originally Posted by imashination: When a surface is curved, the curvature causes that part of the object to receive light and reflections from a large portion of the surrounding image. When a surface is flat, it is picking out a very small part of the sky object to base its illumination off of, this is likely what is causing your grain imho.


Agreed, except that there isn't that kind of grain in the map. Plus, as you watch the animation, the grain is not static. It's like TV static, its constant. Especially the first few frames where the camera is sitting still are just beginning the movement, the noise is constant in it's movement and doesn't speed up as the camera does, which would make sense if it were reflecting noise from the map. Or when you say "base it's illumination off of" are you saying this is a light issue?

Originally Posted by imashination: Seeing as the entire object is the same blurred metal texture though, you can potentially save a helluva lot of render time in this animation. Now this will depend on what else might have to happen in the project, but if it were me...:

Disable GI / indirect illumination, its adding very little to the scene. On that object, 80% of what youre looking at is just reflections on the surface, throw in a pair of large area lights and its going to make very little difference to the visual image but will save you a ton of render time.


True but this is a camera projection scene, so there is a floor, walls, pillars and ceiling and the camera movement is not set in stone. I may start near the ground at the base of the engine and swoop up or come down from an above shot. I can't texture those with the map in the illumination channel as I want the floor to receive shadows (once I do a better job with lighting) and HDRI lighting lights all of those elements evenly. Will the physical renderer cast floor lighting on the engine without GI/indirect? However, I'll give that a try. Also, it may be moot as I'll probably replace the reflective texture on the engine block with a non-reflective aluminum (or aluminium ) texture and then I'll want that nice HDRI lighting where AO isn't quite enough.

Originally Posted by imashination: Next, open your hdri in photoshop and blur the living crap out of it, and save it as a new version. Instead of using blurred reflections in the render engine (sloooooooooooow) just pre-blur the reflective image and use that as the sky (faaaaaast) Use a second crisp copy of the image as the background in the render.


Solves the blurry environment reflection but I need the parts that are reflecting each other to be blurry also. Also, this is a projection map scene made from a backplate, I'm not using a panorama for the background.

Originally Posted by imashination: Thirdly, this model would take post-DOF very nicely. Just add a depth map and blur it in photoshop/AE afterwards.


Agreed, I rendered a new test out last night with OpenEXR multipass and no baked DOF in the RGB.

Originally Posted by imashination: If you do the first two, your render times will plummet, if you do the third too, your render time will probably be 1/100th of the original, and youll be grain-free.


Hopefully. About to drop in some simple objects and render them and see what happens. I'll post those findings shortly.

This kind of felt like the Roy Batty scene in Blade Runner confronting his maker . "I want less grain, ******."
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Old 06 June 2013   #24
Originally Posted by littledevil: First of all sorry about the Indirect Illumination thing, i did not realize that you were referring to the Physical Renderer sub group with that, but now it is making perfect sense.



At least the standard gi engine does. It does produce reflective/refractive caustics without the raytracing caustic engine. I am not sure about the physical renderer though.

Have you enabled GI-Area Light for the HDRI material ? If so, increase your shadow subdivisions to at least 2 (or turn it off, as there is almost no shadow contribution in your image). The last screenshot without DOF also suggests that blurry sampling is having troubles to unify the incoming reflection rays (distant flat areas and areas facing other objects). Have you tried to increase the blurriness subdivisions by the factor 1.5 to 2.0 ?


I don't know what you're saying here. Enable GI-Area Light for the HDRI material? lighting is a blurred HDRI map applied to a sky object and the same map, unblurred, for reflections applied to a separate sky object. Both have the necessary compositing tags for their roles.

I've cranked up blurriness subdivisions to 4, and although better, there's still an unexpected amount of grain.
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Old 06 June 2013   #25
Originally Posted by vid2k2: The angle of incidence is responsible for reflections seen. Hence, rotating the hdri will change
that angle and the reflections on the surfaces.

How are you mapping the material ... uvw, spherical, frontal ? On the sample attached, the
cube on the right is tiled at 25% to minimize any aberrations. The other primitives are 100%
and mapping set to cubic. Simple noise is in the bump channel.

If I were troubleshooting this, I'd dupe the texture and apply it to any flat surface geom,
less any fx like reflection, etc. That should give you no grain at all. Last, for a model like
this I'd pull the default options of ray depth, reflection and shadow back to 6-5-6 rather than
15-5-15

As mentioned, a stripped down scene would help identify other options.

Edit:
Image without bump 5% blurry reflections


The material is mapped UV. Being it's a simple texture with only a reflective and specular channel (no color or bump) I wouldn't think mapping would have any affect? The noise in my images is coming from blurring the reflections. If I put blurring to 0, there's no noise in the flat surfaces.

I'd love to provide a scene, but the maps are commercial and the model is proprietary. It is a CAD conversion, I'm not sure I ever specified that. so I can't provide them. I'll do some simple primitive tests then post a scene with my metal.
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Old 06 June 2013   #26
Quick render of primitives. Interesting. I'll post a stripped down scene shortly.
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File Type: jpg Sphere-And-Cube.jpg (91.9 KB, 48 views)
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Old 06 June 2013   #27
Gotta fix the mapping on that pillar. What a hack.
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Old 06 June 2013   #28
Stripped scene. Not sure if it will help much without the maps. Stripper
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Old 06 June 2013   #29
Originally Posted by Troyan: I don't know what you're saying here. Enable GI-Area Light for the HDRI material?


Material.Illumination.GiAreaLight - enabling this option will cause your material to cast shadows like an area light. large objects will have very soft shadows and will therefore need a very high subdiv to be rendered noise free. in c4d r13 and lower there are multiple settings in the material dialog, in r14 the sampling has been unified with the gi-engine (also for the standard renderer). the option is disabled by default.

however it seems to be an exclusive blurriness problem considering your test scene. one reason why i do not like the physical renderer is, that its values are completely meaningless to me. for the standard renderer i know 32 blurriness samples are low 512 are pretty high. 4 could be a large value or a low value, i simply don't know, but if it did help i would try raising it more while lowering the AA.
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Old 06 June 2013   #30
Finally, screenshots of the lighting and reflective maps.
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File Type: jpg HDRIlightingMap.jpg (33.2 KB, 26 views)
File Type: jpg Reflective-Map.jpg (94.0 KB, 24 views)
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