Samstag, 9. Januar 2010

QMC optimized | Oversampling by material Pt.1

Now let's have a look at the other Oversampling method which is set up via the material manager.


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Remember when it's set to "oversampling" the oversampling is determined by the rendersettings which we dealt with on previous posts. "per-pixel QMC Sampling" is redundant when rendering with QMC-GI.
So we only have the "QMC Sampling" left. The C4D online help recommends to use this Oversampling method for small lightsources so I was especially curious how it works out with the according scenes.
Before improving rendertime/ quality I did a lot of testrenderings to examine how oversampling via materialmanager affects the general outcome.

Here's what I found out along doing these testrenders:
What first struck me is the different result when using Oversampling via Rendersettings versus Oversampling via Materialmanager. The latter will give you a much more defined and contrasty illumination. Pixelsharp shadows are possible. This can result in a more dramatic look:


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At some spots Materialmanager Oversampling appeals somewhat unrealisitc to me. Take a look at the last pic. The area where the GI portals meet the floor there's a brightly illuminated area (Rendersettings Oversampling) that's missing in the Material Manager Oversampling rendering.

The "QMC Sampling" Oversampling will give you clearer shadow/ light definition (primary bounce) but it can not make up for an overall low samplecount (grain) that shows elsewhere in the picture (secondary and further bounces). Take a look at the following examples:

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Note the crisp shadowline at the right! This scenario has a lot of areas that are influenced by first bounce rays thus profiting a lot from the Material Manager Oversampling. Even though the lights are pretty big and the manual recommends to use Material Manager Oversampling for smaller lighsources it was faster to render than with the Rendersettings Oversampling enabled.
More in depth renderspeed/ quality comparisons is what we're going to take a look at next.


Samstag, 2. Januar 2010

QMC optimized | Oversampling in different Scenarios, highly detailed

What happens if some heavy detail is introduced to the existing lighting scenarios?
The GI testscene offers two checkboxes to add intricate detail on the table as well as on the upper right wall.


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With all these nurnies no wonder rendertimes went up (about threefold, therefore I decreased the resolution to keep me sane..)
Also here making use of oversampling did a good job reducing rendertimes while maintaining quality.


The relative speedgain compared to the undetailed scenes was generally maintained or diminished. Only few were a bit faster to render. But nevertheless oversampling was always faster to render than its non-oversampled equivalent with our provided level of detail. I guess there will be a certain amount of detail where oversampling cannot play out its advantage anymore and relying on other optimizations is advisable. But that needs still to be verified.
So far oversampling has been proved to be very beneficial!

Check out the diagrams for a precise comparison of the different scenarios without/ with detailed geometry: