MAXON Computer Cinema 4D Tutorials: Caustics

Tips & Techniques - Lighting

Lighting:
Caustics
Download:
Project Works with:
XL Requires:
Version 7+

With the release of XL Version 7 comes a powerful new set of features to create more realistic imagery. Among these new features are caustics, which are formed by light being reflected or transmitted by a number of specular (shiny) surfaces before interacting with a diffuse (light scattering) surface. The light cast onto a dining table by a wine glass is one of the most common examples of caustics. This tutorial is more of a quick start guide for helping new users set up the basics to add caustic effects to their images.

Step 1: In order to generate caustics, you need three basic elements: a refractive or reflective object, a light to cast photons, and a surface for the caustics to be cast onto. Begin by creating a simple scene to test out different settings. Start by generating some caustics from a metal object.

Open a new scene and create a Tube Object (Objects=>Primitive=>Tube). This object will act as a reflective, metal ring. Double click on the Tube icon to open its settings. Change the Inner Radius to 190m, Rotation Segments to 50, Height to 50m, and Cap Segments to 3. Leave all the other settings as default and click OK.

Step 2: Create a Floor Object for the caustics to be cast onto (Objects=>Scene=>Floor). Now move the Tube so it rests on the Floor. With the Tube Object selected, enter 25m for the Position along the Y Axis in the Coordinates Manager.

Step 3: The next step is to create the materials for the scene. Start by adding a New Material in the Material Manager (File=>New Material). Double click on the text 'New' below the material icon and change the name to 'Copper'. Click OK.

Open the settings for the Copper material by double clicking on the material icon. This material will use four channels: Color, Reflection, Environment, and Specular. Select the Color channel and change the settings so you have a dark brown color, the settings shown here are R=35% G=25% B=15% Br=80%.

Select the Reflection channel and be sure it is active by checking the small box next to the channel name. The reflective property of an object greatly affects the caustic effects that it generates, so you want to have a strong reflection to really bring out the caustics. The reflection color should be a lighter brown; the settings here are R=60% G=35% B=10% Br=85%.

Select and activate the Environment channel. You will load a jpeg image to use for this channel. Change all the RGB settings to 0%. Click the Image button and direct the path to the reflection.jpg file that is included in the zipped project file. Change the Sampling to Circle, change the Mix setting to Multiply, and move the slider to 50%. Select and activate the Specular channel and change the Width to 80% and the Height to 60%.

Before you save this material, check the Illumination settings at the bottom. The Caustics settings should already be active, as well as the Global Illumination options. The GI settings won't affect render times since they will not be activated in the final render settings.

Step 4: Create one more material for the Floor (File=>New Material). Change the name of this material to 'Floor'. You could create a detailed material to add to the realism of the scene, but to speed up render times and concentrate on the caustics, use a simple, white material. Open the Material Settings and select the Color channel. Slide the Brightness up to 100%. Click OK.

Step 5: Apply the Floor material to the Floor by dragging it onto the Floor Object in the Object Manager and releasing. When the Texture dialog opens, leave all the settings as default and click OK.

Repeat the same steps for the Copper material. Apply it to the Tube Object. Be sure the Projection is set to UVW and click OK.

Step 6: Finally, add a Light to the scene (Objects=>Scene=>Light). Move the Light to the following Position in the Coordinates Manager: X=0m Y=500m Z=-700m. Double click on the Light icon in the Object Manager. Set the Brightness to 100% and change the Type to Spot(Round). Turn on Hard Shadows as well. Go to the Details tab and change the Outer Angle to 40.

Select the Caustics tab. Since there is no Volumetric Light, only check the box for Surface Caustics. Set the Strength to 150% and the number of Photons to 600000. Click OK to close the window. Lastly, change the Rotation of the P Axis to -35 in the Coordinates Manager.

Step 7: This will be the basic setup of the scenes. Now to set up the Render Settings (Render=>Render Settings).

Under the General Settings tab, set Antialiasing to Best. Under the Output tab, set the Resolution to 640x480. Select the Caustics tab. Since there is no Volumetric light in the scene, only check the box for Surface Caustics and set the Strength to 90%. Leave the other settings as default. If you wish to save the image to compare different settings later, go back to the Save tab, check the box for Save Image and click the Path button to direct where the file will be saved. When the Render Settings are complete, click OK.

Final image from scene 1

Now to render out this image. Before you do, make the Tube Object editable (Structure=>Make Editable). Position the Tube in the center of the main View Window. Use the Frame Active Object command (Edit=>Frame Active Object). Then begin rendering this scene (Render=>Render to Picture Viewer). While you're waiting, continue on to set up the next scene.

Scene 2:

The second scene will be a small fishtank. Caustics will be visible on the surface of the water as well as the bottom of the tank.

click to view Quicktime movie

Step 8: Create a Cube Object (Objects=>Primitive=>Cube). Change the name of the Cube to 'Glass'. Open the settings by double clicking the icon next to the name. Change the Size settings to X=700m Y=400m Z=400m. Leave the Segments at 1 segment each and click OK. Make the Glass Editable (Structure=>Make Editable).

Step 9: With the Polygon Tool active (Tools=>Polygons), select the top polygon of the Cube and Bevel it in slightly (Structure=>Bevel). In the Active Tool Dialog, enter Extrusion=0m Inner Offset=20m. Finally, Extrude the same polygon in to finish the glass (Structure=>Extrude). In the Active Tool dialog, change the Offset to -380m and click Apply.

Step 10: Add some sand to the bottom of the tank. Create one more Cube (Objects=>Primitive=>Cube) and rename it 'Sand'. Change the Size settings to X=660m Y=20m Z=360m, and click OK. Using the Coordinates Manager, Move the Sand to Y=-190m.

Step 11: To create the body of water, add a Cube object to the scene(Objects=>Primitive=>Cube). Click on the text next to the Cube twice and rename it 'Water'. Double click on the Cube icon, change the Size settings to Width=660m Height=320m Depth=360m, with 50 segments each and click OK. Position the water +10m on the Y axis in the Coordinates Manager.

Step 12: To create materials, you will use the SLA shaders included with the release of XL 7. Start with the most important material in this scene, the water material. Add a new material to the scene (File=>New Material) and rename it 'Water'. Open this material's settings. Select the Color channel and enter the following values: R=85% G=90% B=100% Br=100%.

Select the Transparency channel and be sure it is active by checking the box to the right of the channel name. Change the Brightness to 89%. On the right, check the box for Fresnel and enter 1.33; this is the Refractive Index of water.

When light passes from one object to another, it is refracted because the speed of light varies in the two mediums. The basic formula for finding the index of refraction(n) of an object is (n=c/v), where c=the speed of light in a vacuum, and v=the speed of light in another medium.

Select and activate the Reflection channel. Change the Brightness to 25%. Select and activate the Specular channel. Change the settings to Width=65% Height=45% Falloff=5%.

Select the Displacement channel. Here, you will use bhodiNUT 3D Noise to add ripples to the water. Select the bhodiNUT 3D Noise shader from the triangle pulldown menu to the right of the Image field. With the 3D Noise channel shader loaded, click the Edit button. Change the following settings: Global Scale=200%, Noise=Wavy Turbulence, Octaves=0, Animation Speed=1.7, Cycles=0, High Clip=80%, Brightness=10%, and Contrast=25%. Set the X, Y and Z Scale to 150% as well. Click OK to save these settings. Back on the Displacement channel settings, set the Strength to 40% and Maximum Height to 15m. Click Refresh to save these settings.

Step 13: The next material is for the glass. Use the bhodiNUT Volume shader BANJI (File=>New 3D Shader=>bhodiNUT Volume=>bhodiNUT BANJI). The default settings for this shader create a simple glass texture, sufficient to use in this tutorial, just change the name of the material to 'Glass'.

Step 14: Create another material for the gravel (File=>New Material) and rename it 'Sand'. Open this material's settings and select the Color channel. Click the Image button and load the image gravel.jpg into the Color channel. Select and activate the Bump channel. Click the Image button and load the file gravel_bump.jpg into the Bump channel. Change the Strength to 70% as well.

Finally, select the Specular channel and eneter the following settings: Width=25% Height=10% Falloff=5%. Click Refresh to save this material.

Step 15: Now apply each material to it's respective object. Start with the Glass. Drag and drop this material onto the Glass object. When the settings dialog opens, change the Projection to Flat and click OK. Next, apply the Water material. When the settings dialog opens, make sure the Projection is set to UVW Mapping and click OK. Repeat the same steps for the Sand material.

Step 16: The next element needed for the scene is a Light (Objects=>Scene=>Light). Change the Position of the Light to X=-500m Y=1200m Z=-500m in the Coordinates Manager.

Step 17: Double click on the Light icon to open it's settings. Under the General tab, set the Brightness to 80% and Shadow to Soft.

Select the Caustics tab. Turn on Surface Caustics by checking the Enable box on the left. Set Energy to 150% and Photons to 600000. Click OK to save these settings.

Step 18: Add a camera to get a good perspective of the tank(Objects=>Scene=>Camera). Move the Camera into position; in the Coordinates Manager, enter X=-200m Y=500m Z=-900m H=-13 and P=-30.

Step 19: Open the Render Settings dialog (Render=>Render Settings). Under the General tab, change Antialiasing to Best. Select the Output tab and change the Resolution to 640x480.

Select the Save tab. Click the Path button and choose where you would like your file to be saved. Set Format to JPEG or whatever format you would like to save the image as. Next, go to the Antialiasing tab and set the Threshold to 75%.

Select the Caustics tab. Activate Surface Caustics by clicking the box and set the Strength to 150%.

Step 20: Once the Render Settings are complete, click OK to save the new Render Settings. Before you start rendering, view the scene through the Camera Object. Switch to Perspective View (View=>View 1) and with the Camera selected in the Object Manager, choose Camera=>Link Active Object. Now you are ready to render a clean image (Render=>Render to Picture Viewer).

This scene has also been set up to output a small animation as well, though it will take longer to render out. If you wish to render an animation as well, change the following Render settings: under General, change Filter to Animation; under Output, change Resolution to 320x240, Frame to All Frames, Frame Rate to 15; and under the Save tab, change the Format to Quicktime Movie Small. Be sure to click OK to save these settings.