Ramp Shaders

Ramp Shaders
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by Kenneth Styrberg

Relevant to Blender v2.34

Introduction

In many real life situations - like skin or metals - the color of diffuse and specular reflections can differ slightly, based on the amount of energy a surface receives or on the light angle of incidence.

The new Ramp Shader options in Blender now you allow to set a range of colors for a Material, and define how the range will vary over a surface, and how it blends with the 'actual color' (typically from material or as output of texture).

Since texture calculations in Blender happen before shading, the Ramp Shader can completely replace texture or material color. But by use of the mixing options and Alpha values it is possible to create an additional layer of shading in Blender materials.

Interface

The Ramps panel is located in the Material context (F5). Here you can use the top two buttons to show either settings by pressing Show Col Ramp for diffuse or Show Spec Ramp for specular ramps. (Figure 10.15, “Ramps Panel.”).

Figure 10.15. Ramps Panel.

Pressing the button Colorband enables Ramp Shaders. By default it opens with 2 colors, with the first having Alpha = 0, and no color. And the second having Alpha = 1 and a cyan color. (Figure 10.16, “Ramps Panel Colorband.”).

Figure 10.16. Ramps Panel Colorband.

Add - Adds a new color in the middle of the colorband with neutral grey as default color.
Cur - Displays the current selected color number on the colorband.
Del - Deletes the current position.
E/L/S - Defines the type of interpolation between the Ramp Shader color and the Material color. E - Ease or Qubic, L - Linear and S - B-Spline.
Alpha - Defines how much of the Ramp Shader effect will be seen. An Alpha value of 0 means that the Ramp Shader is totally transparent and will not be seen in the final material. A value of 1 sets the Ramp Shader opaque. If you defined colors with different Alpha values, they will be interpolated between each other to get a smooth transition between different transparency settings. You can preview the Alpha settings on the color band with the checker board pattern behind the colorband. If pattern is visible then the transparency is less than 1.
R/G/B - The current color RGB values. You can LMB on the color field under the Pos field to choose a color using the Color Picker.

The current color is marked with a slightly thicker bar in the colorband. To select a color position you can either press LMB on the desired color position, or step the current color number up and down with the right and left arrows in the Cur field. You can also SHIFT-LMB in the field and enter the required color number manually.

You can move the position of a color by simply pressing the LMB and dragging over the colorband. There is also a Pos field where you can move the position with the left and right arrows or SHIFT-LMB in the field and enter the position manually.

Note

If you reorder the positions of the colors, they will be renumbered so that they always start with 0 from the left and increment to the right.

The two pop-up buttons and the value slider in the bottom of the panel defines how the Ramp Shaders work:

Input

Figure 10.17. Input popup menu.

Shader - The value as delivered by the basic shading formula (like Lambert or Phong) defines the color. Here the amount of light doesn't matter for color, only the direction of the light.
Energy - As Shader, but now also lamp energy, color and distance, is taken into account. This makes the material change color when more light shines on it.
Normal - The surface normal, relative to camera, is used for the Ramp Shader. This is possible with a texture as well, but added for convenience.
Result - All three previous options work per lamp, this option only does it in the end of all shading calculation. This allows full control over the entire shading, including 'Toon' style results. Using alpha values here is most useful for tweaking a finishing touch to a Material.

Method

Figure 10.18. Method popup menu.

The Method menu has several options for blending type: Mix, Add, Subtract, Multiply, Screen, Divide, Difference, Darken and Lighten.

Method options gives an option to choose how the blending between the color from Input and the Ramp Shader will be done.

Factor

Figure 10.19. Factor slider.

The Factor slider denotes the overall factor of the Ramp Shader effect: 0 means no effect and 1.0 means full effect.

Example

Let us make a simple example using Ramp Shaders.

1. Remove default cube object from scene and add a Monkey mesh! (SHIFT-A -> Add -> Mesh -> Monkey). Press Subsurf and set display and render Subsurf Subdivision level to 2. Press Set Smooth to get a nice smooth Monkey! All this in Edit context. (F9).

2. Now press TAB to exit EditMode. Press F5 to enter Material context. In the Material panel press Add New to add a new material! Change the parameters in the Shaders tab as Figure 10.20, “Shader settings.”.

Figure 10.20. Shader settings.

3. Press Ramps tab to open the Ramp Shader panel. Press Colorband to activate the Ramp Shader effect. Now try to set the parameters as Figure 10.21, “Ramp Shader settings.”. Remember to set the Input to Normal. The second color to the right is set to Alpha = 0 and the color to pure black!

Figure 10.21. Ramp Shader settings.

4. In the Ramps tab press Show Spec Ramp and try to set the parameters as Figure 10.22, “Specular Ramp Shader color 0.” and Figure 10.23, “Specular Ramp Shader color 1.”.

Figure 10.22. Specular Ramp Shader color 0.

Figure 10.23. Specular Ramp Shader color 1.

Here is the rendered result of the settings we just entered above. In Figure 10.24, “No Ramp Shader.” there is no Ramp Shader active. In Figure 10.25, “Color Ramp.” the Color Ramp is activated and finally in Figure 10.26, “Both Color and Specular Ramp.” both Color Ramp and Specular Ramp are activated!

Remember here we have just demonstrated one effect of the Ramp Shader. There is much more to explore, try changing the Input and Method parameters, to see totally different results from the ones we have just seen in this example.

Figure 10.24. No Ramp Shader.

Figure 10.25. Color Ramp.

Figure 10.26. Both Color and Specular Ramp.

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