Clamp Direct, Clamp Indirect

Hello Everyone,

I am pretty new to 3D and I was hoping someone could help educate me on something.

I have been working through “Blender 2.6 Cycles: Materials and Textures Cookbook”. As I was going back through the setup after changing to 2.7 I noticed that “Clamp” is now 2 different settings, “Clamp Direct, and Clamp Indirect”.

I was wondering if someone could explain the difference between the two of them, and how those 2 differ from the original “Clamp” setting?

Thanks in advance

See this

Thank you very much, the video was very helpful.

If you’re still having trouble, basically Clamp Direct will clamp the intensity of pixels being hit directly by light sources. This means bright highlights and reflections. Generally you won’t want to clamp this value much, if at all, as these values are important to a linear color pipeline and post production/comp. Indirect clamping will clamp pixels being hit by reflected light. This is a VERY handy tool to have for most scenes. Light paths that bounce from glossy to diffuse multiple times are difficult to resolve and often cause ultrabright pixels or fireflies that will take many passes to average out to a correct result afterwards. Things like hair, materials with fresnel interreflections, and the like are especially prone to this. Clamping this value will ensure that you don’t get any accidental bright pixels during sampling, while also ensuring that you’re not measurably affecting the dynamic range of the final image as a whole.

Thank you very much for that explanation. It is exactly what I needed.

This is a very useful feature… I made these shiny monkey heads to test it out.

  1. No Clamp:

The above render is without any clamp (Direct & Indirect set to 0). You can see the fireflies mainly around monkey’s ears.

Now let us see which of the Clamp setting (Direct or Indirect) removes those fireflies.

  1. Clamp Direct set to 1, Clamp Indirect set to default of 0:

As you can see the direct clamping has messed up the white reflections but did not remove the fireflies.

  1. Clamp Indirect set to 1, Clamp Direct set to default of 0:

The fireflies are gone…! and the white reflections are not affected.

This is a great feature… Until Blender 2.69, I used to be upset that whenever I increase clamp the white reflections get messed up.

It is not an issue anymore… because now you can target specifically the indirect clamp…!

With an Indirect Clamp value of .5 the above monkey head looks even better… No signs of fireflies:

Compared to the monkey head with no clamp:

This was impossible before Blender 2.7 with the single clamp setting…!