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Channel Lighting with Steven Walker

Use of WALKER EFFECTS and CINEMA 4D By Ko Maruyama
There are several keys to creating 3D still images and animations for use within a separate compositor.  This week, Steven Walker, author of plugins called WALKER EFFECTS explains the process of preparing files in CINEMA 4D for use with his After Effects plugins.

Cinema 4D Channel Lighting Tutorial

This tutorial explains how to use Cinema 4D to create render passes that can be used with Walker Effects Channel Lighting in After Effects. A sample 3D scene is provided that demonstrates the use of XPresso to control lighting and materials to facilitate setting up render passes. No special plug-ins or modules are needed in Cinema 4D. For After Effects you will need the Channel Lighting plug-in which can be downloaded as part of the free Walker Effects Professional Demo.

If you have not done so already, please download the required project files: c4dlighting.zip

Steven does not rush through the tutorial with a numbered process that takes 10 steps.  Instead he explains the processes which he completes through the project so that you might understand the concept behind the comp.




Here is an exerpt from his tutorial (reprinted with permission)

Introduction to Lighting Passes     

Before you continue further with this tutorial, it is recommended that you read the Introduction to Lighting Passes.

What About Cinema 4D's Built-in Render Passes?    

You may wonder why lighting passes cannot just be done using Cinema 4D's built-in render passes. There are several issues. First, there is no way to define different groups of lighting. You can create a lighting pass, but only one that represents the whole scene. Second, there are other special considerations that come up that really require total control over the setup. By using XPresso, the built-in multi-pass rendering is skipped and passes are created explicitly.

Project Layout

If you haven't already looked at the sample project, now would be a good time to do so. The first thing you should notice is the organization of the project. A good hierarchical organization of project nodes is critical. Everything is grouped into a few high-level nodes: Cameras, Lighting, Scene.



The primary node that interests us is Lighting. There are 3 direct children of the Lighting group: Ambient Light, Light Instance and Scene Lights.

Ambient Light

This light is used by the Lighting expression to produce the diffuse color pass or otherwise known as an ambient color pass. By setting one light to be 100% ambient and turning off all other lights, every visible surface is rendered at full illumination. To the eye it looks like everything is self-luminant with its material color.

To make an ambient light, you must
turn on the Ambient Illumination checkbox in the Details tab.


For all other purposes ambient light is generally useless, as it serves only to flatten out the color of an image. Nobody should ever misuse ambient light that way!

Light Instance    

This light is referenced by the XPresso script on the Lighting group but is never rendered. The XPresso script uses an iterator to modify lights in the scene and the Light Instance is used as a placeholder to prevent confusing it with a real light in the scene. Do not delete it as it will break the script.

Scene Lights    

This group contains all the lights in the scene. It is possible to setup the scene a different way, but it really simplifies things to have all the lights together in one place. The Scene Lights group contains 3 additional groups: Sun, Sky Dome and Glow. These lights will be rendered into the respective red, green and blue channels.



All the lights in the scene are grouped into 3 categories.

Lighting Limitations    

There is no limitation on the number of lights when using Channel Lighting. There is however a limitation to the number of lighting groups. Channel Lighting can support up to 6 different lighting passes, but a typical image can only store 3 channels (RGB). Therefore to render more than 3 sets of lights would require additional setup and more scripting in Cinema 4D.

The XPresso Script    

Applied to the Lighting node in the Objects panel you will see an XPresso script tag.



The XPresso tag is displayed in the right column in the Objects view.

Double-click the tag icon to open the XPresso Editor.



The XPresso editor contains a visible script in a flowchart-like format. Data travels from left to right.

XPresso is a visual scripting language based on nodes with published input and output values. You create relationships between objects by connecting one output to the input of another. If you are not familiar with XPresso it may be worthwhile taking a break from here and consulting the Cinema 4D documentation to get more familiar with it. XPresso is useable by even the most math-a-phobic!


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Related Keywords:Cinema 4D, Tutorials, Steven Walker, After Effects, Walker Effects

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