Image Map Shader - Effects Tab

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Image Map Shader - Effects Tab

The Effects tab contains settings related to transparency and translucency.

There are some additional settings in TG v3.1.02.0 and newer, Invert Alpha Transparency and Use alpha/transparency for direct blending. Use alpha/transparency for direct blending is a particularly useful new option. Previously it was a bit involved to blend an image with underlying surfaces using the alpha channel of the image itself. You would need to create another image map shader using the same image file and then use that as a mask for the shader. Now you just need to check Use alpha/transparency for direct blending. This can blend the image to underlying surfaces using either the alpha channel from the image or using transparency generated using a key colour.


  • Alpha as opacity: Check this to use the alpha channel of the image for opacity/transparency.
  • Alpha as colour: If this is checked the alpha channel of the image replaces the RGB channels. This effectively displays the alpha channel as a greyscale image.

  • Create transparency: If this is checked then the shader will generate transparency based on a colour from the image. The colour used for transparency is set with the Transparency key parameter.

  • Transparency key: This sets the colour used to generate transparency. For example if you want green areas to be transparent you would set the alpha key to green.

  • Key tolerance: This controls how many shades of colour similar to the Transparency key colour are used to generate opacity.

  • Invert alpha/transparency (TG3): Check this to invert the alpha/opacity/transparency for the image. This will change opaque areas to transparent and vice versa.

  • Use alpha/transparency for direct blending (TG3): If this is checked the alpha channel of the image or generated transparency is used to blend the image with underlying surfaces. If this is not checked then transparency acts a bit like a cookie cutter which puts a hole in the underlying surfaces, preventing them from rendering at all. However when this is checked the image is blended with the underlying surfaces instead of cutting them away, so the colours of the underlying surfaces show through. Here are some example renders:

    Image map alpha no blend.jpg

    Image map alpha opacity.jpg

    Image map alpha direct blend.jpg

    Image with no blending

    Image using alpha as opacity

    Image using direct blending

    These renders are using the shader as a surface layer on the terrain. The red areas of the image being used in the shader are semi transparent. The left render shows the image without any blending. The middle render shows what happens when you check Alpha as opacity. The grey area is the inside of the planet. The image alpha channel has cut a hole in the terrain. The right hand image shows what happens when Use alpha/transparency for direct blending is checked. As you can see the red area is now blended with the underlying surface instead of cutting a hole.

    It's important to note that Use alpha/transparency for direct blending will override the Alpha as opacity setting. If you have Alpha as opacity checked and then check Use alpha/transparency for direct blending you will always get the direct blending behaviour.

  • Translucent: Check this to enable translucency. The slider to the right controls the amount of translucency. Translucency gives an effect of light filtering through a surface. As an example, you might use translucency on a leaf texture to simulate light passing through it. It's not the same thing as opacity/transparency. Translucency is explained in more detail here.

  • Translucency tint: This colour tints the translucency effect. This is explained further here.

Back to: Image Map Shader

A shader is a program or set of instructions used in 3D computer graphics to determine the final surface properties of an object or image. This can include arbitrarily complex descriptions of light absorption and diffusion, texture mapping, reflection and refraction, shadowing, surface displacement and post-processing effects. In Terragen 2 shaders are used to construct and modify almost every element of a scene.

A parameter is an individual setting in a node parameter view which controls some aspect of the node.