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Blurry Reflection

Blurry Reflections are cause by setting the Sharpness settings on the Material Wizard to a low value.

A high value (1.00) set the reflection to be perfect - e.g. for mirrors. A value such as 0.90 lets in a little blur. And lower values let in more and more blur.

More blur requires more passes

For this scene, I have intense light coming in through the window. The direct sun goes to the left, and the center reflection is reflection from the sky. I have set sharpness to 0.15 which creates a very blurry - but sometimes realistic - reflection.

5 passes

After just 5 passes, you can see how the renderer created the blurriness. It has sampled the window reflection as 5 separate pieces - one for each pass. With high blur (low Sharpness), and a low number of passes the looks very unrealistic.

Blurry test-15-5.jpg

40 passes

Even after 40 passes, the effect is not realistic:

Blurry test-15-40.jpg

1,000 passes

However, after 1,000 passes the blur has converged much better and is producing the result desired.

Blurry test-15-1000.jpg

Conclusion: Special lighting effects are going to require lots of passes to have time to converge properly.

Another Example

Here is a sample where the road is marked to have blurry reflection.

The final image, here after 500 passes, has a very blurry effect.

CARP CREEK D SKT-500.jpg

Here is how this is done:

After the first pass, these is just one single sharp reflection on the road:

CARP CREEK D SKT-1.jpg

However, in the second pass a second sharp reflection is generated - creating a choppy effect.

CARP CREEK D SKT-2.jpg

But after this is repeated, over and over, the final blurry reflection is created:

CARP CREEK D SKT-500-crop.jpg

See also