R16 Reflectance render times?


I thought I’d share a few thoughts on “optimizing” reflectance here. I haven’t done any benchmarks but the differences are generally noticeable without a stopwatch.

  1. Use the physical renderer and the adaptive sampler. The quality to speed ratio is just higher than the standard renderer.

  2. Increase Blurriness Subdivisions if you’re using rough reflections. These are targeted subdivisions that will improve the quality of the blurry reflections without adding more subdivision samples to the rest of the scene (where you likely don’t need them).

  3. Don’t use diffuse reflectance. This feature essentially replaces GI if you choose to use it, but it doesn’t have the same level of control over the quality/speed. It’s essentially like running QMC GI with a large diffuse depth (both in terms of quality and render speed). Instead stick to using GI and the Color channel.

  4. Consider enabling Add Grain (Slow) on your Area Lights if using the physical renderer. Not directly related to reflectance but something I’ve discovered in use. I’d never used this before since it warns (Slow) directly in the attribute. However, it’s not slow when using the physical renderer and it improves the lighting dramatically for large or complex (e.g. spline or object based) area lights. If you want to reduce the grain you can increase the Shadow Subdivisions to do that (the Samples attribute has no effect with Add Grain enabled in the physical renderer).

Those are some working tips I’ve developed. Anyone else have some suggestions?


Concerning lighting with reflectance I have found Area lights to be seriously underwhelming when using blurry reflections now roughness in reflectance. At their default setting they appear as a collection of dots when using slight amounts of roughness( say 10%), which to get rid of you have to up the samples massively and add grain as you suggest. I have yet to find a solution to this problem but have considered adding geometry to the light to create a reflecting element and switching off reflections in the light. This however is a little painful if you have loads of lights. Does anyone else have a better way? Past about 50% roughness the dots blur together quite well but it is in the lower values that you really see the issue.


I do see dots in the specular when not using Add Grain. However, those dots go away entirely with Add Grain on (although there is still, erm, grain at low sampling). The reflection seems to be fine with or without Add Grain.


Yeah, these dot are ONLY visibly if you are using the area light for specular highlights…this also happened in previous versions of C4D and is not new to R16.
One thing that might be catching you is that specular strength is default to 20% on a new reflection layer.
If you want a proper reflection of an area light you must use “seen by reflections” in the light details, AND turn down the specular strength.

That said, if you use GGX with wider speculars and area lights you can get some truly beautiful speculars.


Brilliant. That’s great advice. I agree that using it for blurry speculars with values over 50% does give you great looking materials.


Whipped up a little design in ZBrush and threw some dDosmart materials on in photoshop,
then a super quick scene in C4D. 25 minutes total.

Not only am I blown away by this new shader with it's seemingly unlimited options. 
The speed for me is incredibly fast. 

Under 30 seconds for a 1080p render. C4D's advanced render engine and I, are friends again. 



Awesome :slight_smile: I was able to get similar results with Substance Designer. I’m pretty happy with the new options, especially controlling roughness with maps.

Sure - it adds rendertime in cases with several (blurry) reflections. But that’s not a new thing.
One thing you could try is changing the “Ray Threshold” value in the render options. I had success getting faster rendertimes without losing too much quality. Of course it’s always a tradeoff between quality and speed.

Ok, Vray might be faster. But it’s still a big step forward in terms of quality and I think there will be speed optimizations in the future.


I’m wondering how exactly one could translate PBR (Albedo, Roughness, Metalicity) maps you can get from “substance painter/designer” or the likes of Marmoset etc… inside C4D.

Albedo is color, Roughness is roughness, but metalicity? what’s the equivalent, it’s not straight reflection ? is that a map for fresnel values?


Hi Eric, I’m getting into substance designer/painter atm, loving it very much.
I’m wondering if you found some answers on how to use these maps in the reflectance channel allready.

Needless to say that the ability to use the substance files directly in C4D without the use of bitmaps would be… More then welcome!!!

Regards, Robert


Not really. I didn’t play much lately with the demo. Not sure if that the correct way or not. I’m trying the metallic in the reflection strenght/mask of a very reflective map, roughness in roughness, albedo in color.


Hey thanks Eric,

I did not had the time to do so, but I guess Its about time to watch that reflectance series by Tim Clapham that I purchased a while ago. Will keep you informed if I find something useful.

Regards, Robert


Don’t know the program but isn’t that the reflection color? As in: dielectric materials reflect predominantly white while conductors have a reflectance color depending on the surface color? At least its called similar in crazybump for example…


Thanks Cristian,

Actually the metal-map is a grayscale image and dictates whether its a metal or not.
My first guess would be to use it in the layer mask, but I’m not sure.

Kind regards, Robert


Maybe create two instances of the material, one with colored reflections, the other not, and use the “metalic” map mask to drive the blend?


Hi Eric,

You got me confused here, why would you do two instances?
If you want to use a coloured reflection you can put the color in the layer color and still use the layer mask. But maybe I misunderstand?
I did some quick testing, in the first image you see a rendering with a solid grey in the layer mask to approach the same reflection as in the second image which has the metalness map in the layer mask.

Kind regards, Robert


I’m having a hard time imagining a metal that would feature such a large, smooth bevel. That takes away from believability more than any material attributes.


You got me confused here, why would you do two instances?

The idea was to use the map to blend between one layer with “metallic” characteristics, including colored reflection material, conductor fresnel and maybe “maximum” attenuation model, and another one with non “metallic” attributes : average attenuation model, white reflections and dielectric fresnel.

Does it make sense?


Yes that absolutely makes sense, I completely left out the “what would happen if its a non metal”. Thanks for showing me my black hole.

I was actually planning to dive into this and find a good scenario to work with this, but the good folks at allegorithmic told me that they are working on a plug-in for c4d. :thumbsup:

So I will wait and see what it brings.



Hey that’s great news!



Good news indeed about an upcoming Substance plugin for C4D! I love the Allegorithmic products :keenly: