Cinema 4D Handbook: Chapter 6, Part II


All through September I am going through the Cinema 4D, r10 Handbook in hopes of gaining a new skill and better understanding of 3D modeling. I plan to (from here on out) cover two chapters a week (longer chapters will be broken into multiple posts). Stay tuned for new chapters.

Chapter 6: Lighting, Part II

The first part of Chapter 6 covered “real world” lighting set-ups (3-Point Lighting and Environment Lighting). This second part covers lighting situations that are unique to 3D. Just like the first half of the chapter, these tutorials focus less on technical skill and more on theory, and I’m going to treat this post as such (definitions and ideas).

Tutorial 6.3: Global Illumination

Global Illumination calculates the amount of bounced light in a scene. Through GI you can create hyper-realistic images. However, the trade-off is that your render times shoot through the roof. This tutorial covered some ways to optimize the scene for maximum quality with minimal render time.

Auto Light
When you haven’t added any lights to a scene the Auto Light turns on. The Auto Light activates to make sure you can see your scene even if there aren’t any other lights active. It attaches to the camera, and can be turned off in the render settings.
To Turn Off Auto Light:
1) Open Render Settings. Render> Render Settings
2) Click into the “Options” tab.
3) Uncheck Auto Light. *NOTE: If you turn the Auto Light off, and have no other active lights in the scene, it will render as a dark image.

Light Intensity
In the Attributes Manger of any light, you can adjust the intensity (make the light brighter or more dim). When you work with GI it is helpful to raise the intensity over 100%. Having a high intensity will make it easier to light a scene with the bounce light using GI. If you’re trying to mimic sunlight, then an Infinite Light works well. To see the effects of the high intensity bounce light, you need to turn Global Illumination on.
To Turn On Global Illumination:
1) Open Render Settings. Render> Render Settings
2) Click into the “Global Illum.” tab.
3) Check Global Illumination.

Global Illumination
When you go into the Render Settings for Global Illumination, there are a lot of options. “So what’s the magical formula to make it all work? Well, there isn’t one, except patience and trial and error.” I’m a big fan of this concept. Nothing helps you learn something as much as guess and check. But, it helps to know what some of the options mean.
Standard: refers to the type of GI calculation. It defaults to standard, but other settings may work in different scenes.
Strength: refers to how strong the bounced light will appear in the scene. A setting of “0” would mean there was no bounced light, but the GI would still calculate for it.
Accuracy: a lower accuracy number will render fast, but will reduce quality. A high number will reduce noise and artifacts, but will render slower.
Diffuse Depth:  refers to the number of bounces that a light ray will make. High numbers mean longer render times.
Stochastic Samples:  is the number of rays in the scene. High numbers mean higher quality, but longer render times.
Min. Resolution: will reference areas in a scene that the computer doesn’t have to spend a lot of time calculating. EX: the middle of a wall.
Max. Resolution: raises or lowers the parts of a scene that the computer needs to take more time calculating. EX: corners and object intersections.

Ambient Occlusion
Ambient Occlusion darkens the area of Max Resolution, essentially giving shadows to the places normally covered by GI.” Ambient Occlusion helps to lower the render times when using GI.
To Turn on Ambient Occlusion:
1) Open Render Settings. Render> Render Settings
2) Go in “Ambient Occl.” tab and check “Apply to Scene.”

Materials Illumination
GI is greatly effected by materials. Every material has an “Illumination” Channel. Inside of the Illumination Channel, there is an option for Strength, this option can increase or decrease the amount of light that the material will produce. Increasing numbers for the materials doesn’t hugely effect render times, and you can go over 100% for the settings.
To Check the Material Illumination Settings:
1) Double-click on the material in the Materials Manager.
2) Click on the Illumination tab.

With Global Illumination turned on you can create extremely realistic images. But, “just remember that GI is usually a beast that needs to be tames.” There is a high learning curve, and it takes a fair amount of guess and check.

Tutorial 6.4: HDRI Lighting and Shadow Catching

HDRI’s (High Dynamic Range Images) helps to make realistic lighting when compositing 3D objects into a picture of a real place. HDRI scenes are composed of four components: a background with the picture applied, a sky with the HDRI applied, a floor with the same image as the background, and a 3D object. To set up this type of scene, you need to create a plane, sky, and background. You also need to have materials that you load images into.

Material Setup
To Load the Background Image:
1) Create a material and double-click on it to open its editor.
2) In the Color Channel, click on the Texture bar and navigate to the BG image and load it in.

To Load the HDRI:
1) Create a second material and double-click on it to open its editor.
2) In the Color Channel, click on the Texture bar and navigate to the HDR image and load it in.
3) Click on the HDR image in the Texture bar to edit it.
4) Change HDR Gamma to 1. This reduces the light that the HDRI will generate.
5) Load the HDRI into the Luminance Channel, and adjust its Gamma setting to 1.

To Link Materials to Objects:
1) Choose the BG Material, drag and drop it onto the BG object in the Objects Manager.
2) Drop the HDRI Material onto the Sky object.
3) Drop the BG Material onto the Plane object.

At this point the materials are all linked. But, in order for the shadow catching to work right, the projection type for the Plane’s material needs to change. By changing the projection for the Plane, you wont be able to distinguish between the background from the plane, because they have the same material.
To Set the Frontal Projection:
1) Select the material tag for the Plane Object inside of the Objects Manager.
2) In the Attributes Manager, change the “Projection Type” to Frontal.

Compositing Tag
If you were to render the image now, the image from the Sky Object would override the background image. To hide the Sky Image, but maintain the HDRI material, you use a Compositing Tag. You also want to make sure that you have Global Illumination turned on.
To Add the Compositing Tag:
1) In the Objects Manage, right-click on the Sky Object. Navigate to Compositing. Cinema 4D Tags> Compositing
2) In the new tag’s Attribute Manager uncheck “Seen by Camera.”
3) Turn on Global Illumination in the Render Settings. Render> Render Settings

Illumination Channel
Because the HDRI is lighting the whole scene the Plane Object is brighter than the rest of the object and is visible. It is there to catch the shadows, but it needs to look like the background image. To adjust it so it interacts with the lighting differently, you adjust its Illumination Channel.
To Edit the Saturation on the Illumination Channel:
1) Open the Background Material from the Materials Manager.
2) Click into the Illumination Channel.
3) Change the “Saturation” to “0.”

Shadow Catching
The Plane Object will now catch the shadows created by an object and the HDRI lighting. “Because the HDRI was made in the same location as the primitives, the light they receive matches closely to the picture.” If you need to change the angle of the shadows you can move the HDRI.

Stochastic Renders
“Another setting to consider when rendering with HDRI is changing from the Standard GI method Stochastic.” Stochastic renders slower, but it looks at each individual pixel and can add noise and grain. When you’re compositing, noise and grain can help a lot.

The book says, “3D artists often overlook lighting, but it is just as important as good modeling and texturing.” The same is true with film. Lighting can make or break the mood of a scene. I really enjoyed this chapter and I plan to play around with lighting a lot with future models. Chapter 7 is on the basics of animating, and I’ll be working on it tonight. Hopefully it’ll be up tomorrow.

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