Hi TB,
Are there plans to support light falloff in any future revs?
We already support Falloff. What did you try and what did not work?
See "CINEMA 4D Native Lights Support " in
thinkboxsoftware.com/kc4d-light-sources
Was using point lights for my setups. Thank you for the link. I need to look over the information more thoroughly.
Thank you, Bobo.
Jason
So, after some experimentation, I believe I have a better handle on how Krakatoa is handling lighting falloff.
Here is what the “Light Sources In Krakatoa For CINEMA 4D” says about lighting falloff:
Decay (Falloff)
In Krakatoa, the Falloff is exposed as an Exponent.
Supported CINEMA 4D Falloff types and their corresponding Krakatoa counterparts are:
None - no falloff (Decay Exponent 0)
Linear - linear falloff (Decay Exponent 1)
Inverse Square - inverse square falloff (Decay Exponent 2)
Step - no falloff, same as None (Decay Exponent 0)
Inverse Square Clamped - inverse square falloff, unclamped (Decay Exponent 2)
“In Krakatoa, the Falloff is exposed as an Exponent”.
Does this mean that the lighting falloff is exposed ONLY using the settings in the “Lighting and Drawing Pass” section of the Options tab?
If so, it’s just a bit different from how I am used to working with falloff and decay in Cinema 4D (with both geometry and the X-Particle shader).
As an example, see the images below. That basic scene is using a point light and a basic X-Particle material on the emitter. The point light is set to inverse square falloff and for all intents and purposes, the “closer” the light is to the particles, the hotter the effect of the light is on the particles.
This is not the effect I seem to be getting in the Krakatoa renderer. The distance of the light in relation to the particles makes no difference to how hot, or bright the lighting effect is. In fact, changing the falloff of the C4D light to anything other than “none” in the light’s falloff drop down menu actually results in no light being cast at all.
Please note, I am NOT trying to compare the X-Particle material or render to the Krakatoa renderer, rather just trying to understand how Krakatoa handles lighting falloff.
I should also note, using point lights in the scene below was probably a bad example. I was using spot lights and other types of lights in the Krakatoa scene I was experimenting with earlier, but the result was the same as indicated above.
Something is wrong in your setup, or your Krakatoa build.
The Help mentions the Exponent because we used to have (during the Beta) a Krakatoa Light Tag that would let you set cubic and higher falloffs.
Basically, No Falloff is set to Exponent of 0 (because any number to the power of 0 is 1.0, so the light would never be modified).
Linear falloff would have Exponent of 1 - the farther you go, the less light you get, in linear fashion.
Inverse Square would have Exponent of 2 - the intensity would fall off based on the square of the distance.
So Krakatoa allows you internally to fall off with the cube of the distance by setting the Exponent to 3, but this is not exposed anymore in the shipping build because we removed the Light Tag.
So I created a Sphere.
Turned into a PRT Volume.
Switched Jitter On.
Created a Point light next to it.
Set the renderer to Krakatoa, set the Density Exponent to -2, enabled background color override to blue.
*Rendered in the Picture Viewer.
RESULT: No Falloff, the sphere was lit as expected.
*I then switched the light to Linear falloff and rendered.
RESULT: The Sphere was barely visible, nearly black on the blue background due to the falloff.
*I switched to Inverse Square and rendered.
RESULT: The Sphere was pretty much black.
*I then increased the Intensity of the light from 100% to 1000% (10x stronger).
RESULT: Linear Falloff looked now similar to the No Falloff with 100%, No Falloff was overblown, and Inverse Square was still quite dark.
So it works for me. I might post screenshots a bit later…
Of course, if you are rendering in Additive or Emissive mode, the light will do nothing…
Hi Bobo,
Thank you for the response. I should have clarified my Krakatoa set-up.
I have been using a “Krakatoa PRT Loader” from a PRT sequence created from an X-Particles emitter with some turbulence. I am using Krakatoa Version 2.3.0. The result using a “Krakatoa PRT Loader” is the same as I described above. Using falloff in a light does not yield lighting results.
I have not tried using a PRT Volume as a particle source. Does Krakatoa’s falloff lighting only work with PRT Volumes, or should falloff also work with PRT Loaders?
I will try your setup with a PRT Volume and let you know if I get the same results as you have described in your set up.
Thanks,
Jason
Ah - success…
Based on your feedback here:
*I then increased the Intensity of the light from 100% to 1000% (10x stronger).
RESULT: Linear Falloff looked now similar to the No Falloff with 100%, No Falloff was overblown, and Inverse Square was still quite dark.
I increased a point light’s intensity to 3000% using linear falloff with the PRT Loader scene and started to get results.
I wasn’t pushing the intensity far enough. I should have tried that earlier, but thought smaller values in the intensity would have yielded results.
Thanks for the insight.
- Jason
They should have worked if the scene size is reasonable. The falloff in Krakatoa is kinda physical. If you have a certain light flux and change the falloff settings, the total amount of energy is distributed differently, but remains the same. In other words, with an Inverse Square, in Krakatoa the core area very close the the light will get very “hot”, but the energy of the light will be preserved. Typically, you must increase the intensity of the light to get the light to reach farther when using a falloff. What I did not understand from your screenshot is why you were even seeing any color on the particles - if a Falloff mode was enabled and intensity was low, you should have seen nearly black particles, not green ones. Hence my comment about Emission and Force Additive modes which would override the lighting.
Lighting in Krakatoa is inseparable from shadowing. In your screenshot, I could not see any shadowing of the particles by other particles. So something was definitely wrong, but without seeing the actual scene, I cannot tell what it was.
All particle sources in Krakatoa are equal, and processed the same. They are all just points with Position, Color, Density and possibly some other channels. So a PRT Volume, PRT Loader, Krakatoa XParticles source and whatever should all behave the same given the same data in their channels. Scene scale has a profound effect on the calculations though, so that is something to keep in mind…
Hi Bobo,
Thank you for the explanation of scene scale.
To clarify, the screenshots were from a scene using only X-Particles and the X-Particle shader (not using Krakatoa as renderer) to show you the type of falloff I was used to seeing with lights and decay.
I’m good now that I am seeing results using Krakatoa. Appreciate the responses and the feedback very much! Thank you!
- Jason