Important Workflow Changes In Krakatoa v1.5.0 And Higher

Overview

The addition of new features in Krakatoa v1.5.0 requires some workflow changes you should be aware of when coming from Krakatoa v1.1.x.
This page will discuss the differences in lighting and shading and hopefully ease the transition of existing users.

Workflow Changes

Default Illumination

Neither version of Krakatoa supports the default lights of 3ds Max, mainly because the single behind-the-camera headlight which is the current default does not produce good shading in most cases.
In Krakatoa v1.0.0 up to v1.1.3, rendering particles without any lights assumed a Self-Illumination of 100% to make the particles visible.
In contrast, rendering particles without any lights in Krakatoa v1.5.0 and higher will produce black particles (on typically black background) with only the Alpha channel showing a visible result.
- This was necessary because v1.5.0 introduced the ability to specify and use the Self-Illumination (Emission) per-particle, making any implicit Self-Illumination a counter-intuitive idea - Emission should only be rendered if the user explicitly requested it.
- Enabling Emission is as easy as checking the >Use Emission and >Override Emission checkbuttons in the Main Controls rollout or alternatively in the Global Render Values rollout.
- Since the default Emission Override Color is White, all particles will render white unless they specify their own Emission channel in the PRT file or via KCMs.
- This approach also lets you quickly apply a map to all particles by specifying an Emission Override map (preferably a 3D procedural one, unless your particles have a valid UVW channel).
- If you prefer to get the Color of the particles rendered as Emissive, you can create a Global Channels Override set in the Global Render Values rollout and set the global KCM to copy the Color channel of all particles into their Emission channel. Uncheck the >Override Emission option but keep the >Use Emission option checked and your particles will render in their source color.
- Last but not least, you can always create a light in the scene to get the real illumination with shadow casting, but this will be generally slower since it involves attenuation processing.

Use Lighting Vs Ignore Scene Lights

Another major difference between v1.1.x and v1.5.x is how the lighting is enabled and disabled.
In Krakatoa v1.1.x and earlier, a large >USE LIGHTING button which was unchecked by default was used to switch between the above-mentioned implicit Self-Illumination mode and the use of scene lights.
In Krakatoa v1.5.x, lighting is always on so the button was removed.
- It was replaced by a smaller button >Ignore Scene Lights which simply lets the renderer assume all lights in the scene are turned off.
- Ignoring the scene lights makes sense when the user has provided explicit Emission channels to make the particles fully self-illuminated and is equivalent to deleting or turning off all lights in the scene.
- Lighting will also be ignored automatically when the >Force Additive Mode options described below is checked.

Additive Shading

In Krakatoa v1.1.x, Additive Rendering was a distinct rendering mode as opposed to Volumetric Rendering.
- Krakatoa used a different algorithm to draw the particles in that mode and mixing Volumetric with Additive rendering was not directly possible.
In Krakatoa v1.5.0, the full volumetric shading equation with Scattering (Color), Absorption and Emission terms lets the user control how much color is scattered into the eye, how much is absorbed from each color component as light passes through the particles and how much light is emitted by the particles.
- Since Additive rendering is simply fully Emissive rendering lacking Scattering and Absorption completely, it is now possible to define PER PARTICLE whether it should shade volumetrically, additively, or somewhere in-between.
- You can find more info about controlling and mixing Additive and Volumetric Shading here.
To allow the quick rendering of ALL scene particles in additive fashion though, a >Force Additive Mode option was added to the Main Controls rollout.
- When checked, the content of the Color channel will be copied internally into the Emission channel, while the Color and Absorption will be set to black, producing fully additive rendering like in v1.1.x.
- When this option is active, the content of the Emission, Color and Absorption channels will be manipulated internally, thus the >Use Emission and >Use Absorption options will be grayed out.

Conclusion

As you can see, Krakatoa v1.5.x is a lot more flexible and provides per-particle channels for the main shading values.
These improvements dictated changes in the typical rendering workflow, but this should be a small price to pay for the amazing new capabilities available to you.
Understanding the processes going on inside the renderer and the logic behind these changes should help you master the new version and lose your old habits built in the less advanced environment of Krakatoa v1.1.x.