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Rendr Quality

 
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sasidhargs
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PostPosted: Mon Apr 09, 2012 5:47 am GMT    Post subject: Rendr Quality Reply with quote

Hi, I am new to houdini
pl . give me an appropriate setttings for mantra node to gt more sharp image - I tried so many settings but not able get the optimum antialiasing.

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jeff
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PostPosted: Mon Apr 09, 2012 10:43 am GMT    Post subject: Reply with quote

Try increasing Shading Quality for Micropolygon rendering on object(s) or the global Shading Quality Multiplier on the ROP. Careful with values above 3.
Try a different sharper Pixel Filter in the ROP Output tab (big effect on textures) like catmull-rom at 2x2 or blackman at 2x2 but watch out for ringing.
Try increasing Pixel Samples in ROP Samples tab to improve geometry sampling for raytrace/pbr.

----

Mantra along with RenderMan and the other REYES based render engines at their default settings can be described as having a soft look. At production film resolutions, 2k - 4k, the soft look starts to get sharp and fits in well with live action film plates. If you are using Apprentice, you are very limited in resolution. HD is not as limited and just shy of 2k which is a decent resolution.

Resolution always wins.
Then there's the old school apporach of rendering at 2x final resolution at lower filter settings, then scaling down in comp with filters chosen to suit as a last ditch solution.

You have control over the final look though: what is sharp and what is soft.

With any render engine, when you are referring to blur vs. sharp, it can mean two things:

- Geometry filtering
- Texture/Pattern filtering

See the attached Houdini scene file for a simple set-up to test geometry vs texture filtering. One object is a simple patch to test texture filtering, the other is an array of fine lines to test geometry filtering.
Warning: If you use IPR to preview micropolygon rendering settings, turn off the Preview option. Preview option uses raytracing even if your specified ROP is set to micropolygon rendering. Leave Preview on for raytrace or PBR renders.

Geometry filtering comes up as an issue when you have a lot of very fine displacements on geometry, very fine or thin geometry facing the camera, rendering a lot of curves as in fur/hair. Silouette edges of geometry are directly affected by geometry filtering.
Look at:
- Shading Quality when using Micropolygon render engine.
- Pixel Filter on the Mantra ROP's Properties > Output tab.
- Pixel Samples when using raytracing and pbr render engines.

Texture filtering comes up as an issue when you have texture maps with a lot of information (fine text is an example), very high frequency in procedural noise, basically anything that defines a color on a piece of geoemtry.
Look at:
- Pixel Filter on the Mantra ROP's Properties > Output tab.
- Pixel Samples for all render engines
- Shading Quality for Micropolygon rendering
- Material Shader Color Map Filter applied to the texture look-up.

As you can see, most every control on Geometry Filtering will also improve the texture/pattern filtering as well. This is especially true with Shading Quality.

MicroPolygon rendering is quite different than raytrace, PBR or volume rendering. It is still unique to have a renderer with quite a few engines and balancing all the various parameters to determine image quality is challenging. Houdini tries to overload parameters with like behaviour to work similarly across the four key render engines.

http://www.sidefx.com/docs/houdini12.0/rendering/renderquality


Shading Quality
You can find the shading quality parameter on each object's Render > Shading Quality parameter.
When using Micropolygon Rendering, this parameter plays a large role in the render pipeline. It determines how finely Mantra needs to cut up or dice the geoemtry wrt the camera plane. By default a value of 1 results in your geometry being diced in to the size of a pixel. This pixel is then sampled by firing rays at it (sample rate).
The smaller the micro-polygons, the smaller the geometry is diced, the sharper or more accurate the surface will be. Each micropolygon is then sampled by firing rays at the tiny bit of surface to determine the final color.
Smaller geometry = more rays = higher quality = much more memory consumed = slower render times.
This definitely improves geometry quality at a cost.
A value of 2 means that you now have four tiny surface patches for every pixel. A value of 2 means 9 small patches. A value of 3 is bordering on extreme. A value of 5 is insane imho! Unfortuately some shaders are written in a haphazard way with imperfect internal filtering and can only be solved by extreme shading quality values.

Pixel Filter
The Pixel Filter is run on the full 32 bit pixel data to soften the final result to reduce/eliminate any high frequency noise generated by Mantra. It defaults to Gaussian 2x2, a good default but somewhat soft. If you don't believe me, try gaussian 6x6. LOL!
Experiment with Catmull-Rom 2x2, Blackman 2x2 or if this a still image, go all the way with an all out sharpening filter like sinc 2x2 but in no way use sinc for a sequence and you have been warned. Even Catmull-Rom and Blackmann can cause ringing in sequences. If you've used Photoshop then you have run across filter artefacts when resizing images. Same goes here.

Geometry Filter Width.
For very fine geometry such as hair/fur, this will add opacity for very thin geoemtry.

Look here:
http://www.sidefx.com/docs/houdini12.0/props/mantra
to read about the render properties mentioned above for more info.


Hope this helps you out.



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sasidhargs
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PostPosted: Tue Apr 10, 2012 12:21 am GMT    Post subject: Rendering Quality - exercise Reply with quote

Than Q Jeff ,
I got full work to do , since you gave me a big list of exercises to do.

I will study each and every point you mentioned and post the details.

thanks for scene file. Very Happy

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sjmcc1
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PostPosted: Tue Apr 10, 2012 4:13 pm GMT    Post subject: Reply with quote

I just want to say thank you for such a thorough and detailed explanation. I definitely just learned some things.
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sjmcc1
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PostPosted: Tue Apr 10, 2012 4:13 pm GMT    Post subject: Reply with quote

I just want to say thank you for such a thorough and detailed explanation. I definitely just learned some things.
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jkunz07
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PostPosted: Tue Apr 10, 2012 5:19 pm GMT    Post subject: Reply with quote

Does anyone use sinc 3x3? I've started to use it when doing the blurring in post. I haven't tried it with a sequence but would 3x3 get rid of the ringing or artifacts that would be present in a 2x2 sequence?
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kwejk
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PostPosted: Mon Apr 16, 2012 5:38 am GMT    Post subject: Reply with quote

also higher z-importance can help with displacements at low angles. dicing the geometry more in depth. Smile
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jeff
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PostPosted: Mon Apr 16, 2012 1:32 pm GMT    Post subject: Reply with quote

Yep. z-importance is the "render ocean with displacements to the horizon" render property to help with dicing the geometry finer in the z-direction. I haven't had cause to use it any other time that I can remember.


As for sync, the larger the radius the more potential ringing you will get. Have a look at Mitchel which might behave better with larger filter sizes.

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