Differential D1044 Diff 3315 manual/composite_nodes/types/converter/color_ramp.rst

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manual/composite_nodes/types/converter/color_ramp.rst


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				ColorRamp Node
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				The ColorRamp Node is used for mapping values to colors with the use of a gradient.
				It works exactly the same way as a
				:doc:`Colorband for textures and materials </render/blender_render/materials/properties/ramps>`,
				using the Factor value as a slider or index to the color ramp shown,
				and outputting a color value and an alpha value from the output sockets.

				By default,
				the ColorRamp is added to the node map with two colors at opposite ends of the spectrum.
				A completely black black is on the left
				(Black as shown in the swatch with an Alpha value of 1.00)
				and a whitewash white is on the right. To select a color,
				:kbd:`LMB` click on the thin vertical line/band within the colorband.
				The example picture shows the black color selected, as it is highlighted white.
				The settings for the color are shown above the colorband as (left to right): color swatch,
				Alpha setting, and interpolation type.

				To change the hue of the selected color in the colorband,
				:kbd:`LMB` click on the swatch,
				and use the popup color picker control to select a new color.
				Press :kbd:`Return` to set that color.

				To add colors,
				hold :kbd:`Ctrl` down and :kbd:`Ctrl-LMB` click inside the gradient.
				Edit colors by clicking on the rectangular color swatch, which pops up a color-editing dialog.
				Drag the gray slider to edit Alpha values. Note that you can use textures for masks
				(or to simulate the old "Emit" functionality)
				by connecting the alpha output to the factor input of an RGB mixer.

				To delete a color from the colorband, select it and press the Delete button.

				When using multiple colors,
				you can control how they transition from one to another through an interpolation mixer.
				Use the interpolation buttons to control how the colors should band together: Ease, Cardinal,
				Linear, or Spline.

				Use the A: button to define the Alpha value of the selected color for each color in the range.


				Using ColorRamp to create an Alpha Mask
				=======================================

				A powerful but often overlooked feature of the ColorRamp is to create an Alpha Mask,
				or a mask that is overlaid on top of another image, and, like a mask,
				allows some of the background to show through.
				The example map below shows how to use the Color Ramp node to do this:


				.. figure:: /images/Manual-Compositing-ColorRamp_alpha.jpg

				Using the ColorRamp node to create an alpha mask


				In the map above, a black and white swirl image, which is lacking an alpha channel,
				is fed into the ColorRamp node as a Fac tor. (Technically,
				we should have converted the image to a value using the RGB-to-BW node, buy hey,
				this works just as well since we are using a BW image as input.)

				We have set the ColorRamp node to a purely transparent color on the left end of the spectrum,
				and a fully Red color on the right. As seen in the viewer,
				the ColorRamp node puts out a mask that is fully transparent where the image is black.
				Black is zero, so ColorRamp uses the 'color' at the left end of the spectrum,
				which we have set to transparent.
				The ColorRamp image is fully red and opaque where the image is white (1.00).

				We verify that the output image mask is indeed transparent by overlaying it on top of a
				pumpkin image. For fun, we made that AlphaOver output image 0.66 transparent so that we can,
				in the future, overlay the image on a flashing white background to simulate a scary scene with
				lighting flashes.


				Using ColorRamp to Colorize an Image
				====================================

				The real power of ColorRamp is that multiple colors can be added to the color spectrum.
				This example compositing map takes a boring BW image and makes it a flaming swirl!


				.. figure:: /images/Manual-Compositing-ColorRamp_Colorize.jpg

				In this example, we have mapped the shades of gray in the input image to three colors, blue,
				yellow, and red, all fully opaque (Alpha of 1.00). Where the image is black,
				ColorRamp substitutes blue, the currently selected color. Where it is some shade of gray,
				ColorRamp chooses a corresponding color from the spectrum (bluish, yellow, to reddish).
				Where the image is fully white, ColorRamp chooses red.