When you define the color of an object’s material, you should work with a white light because colored light sources affect the material’s appearance. You can color your light source afterward to achieve the final look of the scene.
Every light is defined by a light shader. All light sources need a light shader, such as the built-in soft_light shader or a custom light shader you built and linked in with the Softimage SDK. A light’s shader describes the light’s color, falloff, and other settings.
Regardless of which light shader you are defining (even custom ones), you can edit its properties in its property editor. The properties you can define depend on the particular shader: they include the light color, attenuations, and spotlight directions.
You can edit and perform a number of operations on a light shader:
• You can save properties as light shader presets and apply them to another light shader of the same type in your scene. See Saving and Loading Shader Presets [ Material and Shader Basics ].
• You can animate a light’s properties so that the values change over time. For example, you can make a light gradually change color or grow dim. For more information on how to do this, see Animating with Keys [ Animation ].
• You can detach a light shader and replace it with another shader of the same type. For information on attaching and detaching shaders, see Applying and Editing Shaders [ Material and Shader Basics ].
The color of a light controls the color of the rays emitted by the light. The final result depends on both the color of the light and the color of objects.
For example, a red object reflects red light, but absorbs blue and green light. On the other hand, a yellow object reflects both red and green light, but absorbs blue light. If you illuminate a yellow object with a blue light, it appears dark. Objects illuminated by white light appear in their natural colors.
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When you define the color of an object’s material, you should work with a white light because colored light sources affect the material’s appearance. You can color your light source afterward to achieve the final look of the scene. |
To set a light’s color
1. Select a light in the viewport and choose Modify > Shader on the Render toolbar to display the selected light’s property editor.
2. In the light’s property editor, set a color for the light.
The current color is shown in the box to the left of the color sliders and under the light’s name. You can set the color using the color sliders or by opening the Color editor. You can also toggle between the RGB, HSV, and HLS color channels.
3. Do one of the following:
- Drag the color sliders to change the strength of each red, green, and blue channel independently, or type a numerical value directly in the space provided.
The slider values range between 0 and 1, but you can enter higher values yourself. Hold the Ctrl key to move all sliders at once.
or
- Click the color box to the left of the sliders to open the Color editor. For information on using the color editor, see Defining Color Properties [ Interface and Tools ].
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You can also drag and drop a color from one color box to another. For example, if you have two property editors open, click on a color box and drag its “color chip” from one property editor to another. Drop the “chip” directly onto the color box you wish to edit. |
The intensity of a light is controlled indirectly through the strength of its separate color channels. If you want to adjust the strength of a light without changing its color, you can use the HSV or HLS color models and adjust V (value) or L (lightness).
Click on the RGB button beneath the color box of a light’s property editor. To set values higher than 1 for a stronger light, type directly in the box to the left of the slider.
Falloff refers to the diminishing of a light’s intensity over distance, also called attenuation. This mimics the way light behaves naturally. These options are available only with point and spotlights.
You can set the distance at which the light begins to diminish, as well as the distance at which the falloff is complete (darkness). This means you can set the values so the falloff affects only those features you want. In addition, you can control how quickly or slowly the light diminishes.
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A light’s falloff parameters are sometimes defined in conjunction with a depth-fading shader or an atmosphere shader, such as in a smoky bar or heavy fog. See Shader Basics [ Material and Shader Basics ] for more information on applying and defining shaders. |
You can set the falloff value using the light’s property editor or its 3D manipulators.
To set the falloff from a property editor
1. Select a light in a viewport.
2. Choose Modify > Shader from the Render toolbar to display the selected light’s property editor.
3. In the Light property editor, select the Falloff option.
4. Set the required Falloff Start and Stop distance values in the Attenuation controls.
5. On the General tab, choose what type of falloff you want: Linear or Use Exponent:
- Linear falloff is sharper and less realistic. When selected, the Exponent parameter is automatically set to 1.
- Use Light Exponent falloff is an inverse square falloff, which is more natural and realistic.
This option uses the value in the Exponent field to determine the falloff. The default value is 2. A high value such as 5 causes light to fall off very quickly, whereas a smaller value such as 0.1 makes the falloff more gradual.
6. Show whether you want the light to be diffused or not by selecting either the Diffuse Only or the Diffuse and Specular option.
Diffusing softens the light and removes its specular highlight; that is, specular values are no longer computed.
To set the falloff using 3D manipulators
1. Select the spotlight or point light for which you want to set the falloff.
2. Press b to display the light’s 3D manipulators.
3. Press Tab until the light’s start and end falloff manipulators appear.
4. The exterior cone-angle control displays a light blue start falloff disc (if falloff is already activated, you see this before displaying the 3D manipulators).
Ctrl+click the disc at the base of the white cone angle cone to activate the falloff.
5. Click and drag this disk toward or away from the light to set the Start value.
6. The exterior Cone Spread control also displays a magenta end falloff disk at its base. Click and drag this disk toward or away from the camera to set the End value.
7. Shift+click and drag either disk to increase or decrease both Start and End Falloff values simultaneously. The distance between the planes of each disk remains the same.
8. To deactivate falloff, Ctrl+click either the start or end falloff disk.
Autodesk Softimage v.7.5