How did I break the "Fast Glossy Interpolation"?

[robkar97]

I have this strange problem I can't figure out how to solve, other than doing a Reset. Some way I have disabled the blurry reflections made through "Fast (Interpolate")... they just render out like a perfect mirror - even though the glossiness is 0.5. I've ticked the checkbox, set it to lookup 3-5 points and form 1 to 1/5 of the resolution. The Glossy samples are left at 0, since I want it to render quickly.

 

If I disable Fast (Interpolate) and crank up the glossy samples, it renders nicely but takes a long time.

 

After a File > Reset, it works the way I'm used to.

 

What am I missing!?

 

Robert

[pixelperfectg]

The Glossy samples are left at 0, since I want it to render quickly.

 

If I disable Fast (Interpolate) and crank up the glossy samples, it renders nicely but takes a long time.

Sounds like you answered your own question. Increase the samples. If you want glossy interpolated samples, leave interpolated checked...but you'll still need to increase the samples.

[robkar97]

Hmmm... the Help files (Arch and design material chapter) claims that to obtain very fast rendering glossy reflections, "Glossy samples" can be left at 0 (true mirror) and yet the interpolation will create the impression of blurriness... or have I misunderstood something?

[pixelperfectg]

or have I misunderstood something?

I believe it's a misunderstanding.

 

This is what the help file states on the subject:

"For slightly blurry but also very weak reflections, you can “cheat” by applying a lower Reflection Glossiness value for broader highlights while setting Reflection Glossy Samples to 0. This shoots only one mirror ray for reflections, but if they are very weak, the viewer can often not really tell."

 

-and-

 

"Note: If you set Glossy Samples to 0, the reflections take the form of a “perfect mirror” and only one ray is shot, regardless of the actual value of Glossiness . You can use this to boost performance for surfaces with very weak reflections. The highlight still respects the Glossiness value."

 

Therefore, if your lights are generating specular highlights (they do by default) those highlights will respect the glossiness values and spread out as you decrease the glossiness value. However, the 'actual' reflections will not blur.

 

For stronger glossy reflections, you'll have to use samples regardless of whether you're using the interpolation method of calculation or not.

Edited June 29, 2008 by pixelperfectg

[robkar97]

Ok, this would explain things! Thanks!