It may be a C4D related issue, but since we are meant to use very small values in certain places e.g. “Particle density 0.0001 or less and even 0.000000001”, C4D turns anything lower than 0.001 to 0
Is there a way to see the actual value?
This is indeed a current limitation in cinema 4d I am afraid. But despite showing 0, the actual value you typed in is kept/used/applied.
I will suggest a solution (hack), because if 0.0001 and 0.00000001 are displayed as 0, then we won’t be able to know what’s the actual value.
Can’t we have something like “x10^-3” to indicate how many zeros go after the decimal point?
Or maybe a text field with the actual number for feedback?
Density seems to be a very important parameter not to be visible.
I’d rather implement a general multiplier to ensure the densities and other respective values in that range get interpreted properly in the first place;)
Currently the whole scene scaling is off as well so the DOF doesn’t behave as expected…
Uhm, have you looked at the Render Settings dialog? 
3ds Max has the same issue with precision in value spinners (although it is customizable, but defaults to 3 decimal positions).
Normally, when you set up your particles, the density should NOT be set to a very low value. By default, each particle comes with a value of 1.0 unless specified otherwise, and particles generated by Krakatoa Mesh Source (aka PRT Volume in other apps) adjust their density based on the voxel size and count per voxel.
Read here, it is about KMY, but still applies to all Krakatoa implementations:
thinkboxsoftware.com/kmy-vol … rendering/
So when you start rendering your scene and the particle density is too high, you usually don’t go to each Krakatoa Source and tweak its Density via a Channel tag, you go to the Render Settings dialog and dial down (or up) the Final Pass and Lighting Pass Density settings.
Since the very beginning of Krakatoa, these settings come, as you proposed, as a base value and an Exponent. The default values are Final Pass Density 5.0, Final Pass Density Exponent -1, producing a value of 0.5. If you want a value like 0.0000005, you just change Exponent to -7 to get 6 orders of magnitude less density. This way, the relative density between all objects is retained and the global density of the scene is adjusted to match your needs.
Of course, if you want one source to have 10 times less density than another, you could put a Krakatoa Channel Set tag and set the Density to 0.1 instead of 1.0, but still leave the global scaling to the controls in the Render Settings dialog.
The Krakatoa C4D exposure currently lacks the very important workflow-wise “Use Lighting Pass Density” and “Use Emission Strength” checkboxes. They were just not implemented and they should be, I will make sure of it next week. The typical workflow is to set the Final Pass Density only, and let the Lighting Pass Density use exactly the same values. This way, there is only one set of controls to tweak that affect all global density scaling options.
Then in some cases, you might want the Lighting Pass to “see” the particles as less dense than the camera does to let more light pass through - see the tutorial about PRT Volume rendering in Maya here which applies to all Krakatoa implementations:
thinkboxsoftware.com/kmy-ren … rt-volume/
Currently in Krakatoa C4D, you have to constantly tweak 3 sets of controls (6 spinners) to keep everything in sync, and that is simply not a good workflow. So if you want your lighting to be reduced when you reduce the final pass density, you have to adjust both Final Pass and Lighting Pass controls. If you are using Emission, you also have to adjust that.
Once we get some C4D-specific documentation posted, some of these approaches will become clear. Right now, I advise you to take a look at the existing Krakatoa MX and MY documentation as the ground principles still apply, and the naming of controls is mostly the same in all implementations.
Hope this helps.
Thanks for the replies.
I’m new to Krakatoa, so you may need to bare with me.
Can we apply the same exponent value to the Particle Source Override Density as well?
Also, for the layman, how “easy” would it be to have an actual representation (not directly editable) of the decimal value next to the exponents?
e.g. Density 5, Exponent -3, actual value 0.005
That way it would be easier for a user to transfer values from Max and Maya tutorials without doing “math” in their heads.
I don’t know how easy it is to do (I assume it is, but I am not involved directly in the programming). But I am heavily involved in the UI design of the Max and Maya implementations. Neither Max not Maya have Exponent in their UIs except for the actual Render Settings dialogs, and C4D has that too. Once again, there is NO NEED to enter 0.005 or 0.000005 in the Particle Source Override Density. You should try to keep your settings around 1.0 (they default to that anyway), and use the Final Pass Density to scale up or down to match the scene scale.
If you want to have different densities between two objects, say two particle systems where the one should render 100 times less dense than the other, you can set the one to Density Override of 1.0, the other to 0.01, or the one to 10.0 and the other to 0.1, or 100.0 and 1.0. Then go to the Render Settings and tweak the Final Pass Density and Lighting Pass Density Exponents until you get the desired look. But the two systems’ densities will remain 100 times apart relatively speaking…
There are no set in stone values for the Render Settings, as they depend on the scale of the scene, the sources you use, the number of particles, the image resolution etc. So most of the test rendering time is spent fine-tuning the global density scale using Final Pass and Lighting Pass Density and especially their Exponents.