Applying an Alphamap

If you want parts of your model to be transparent then you can use an alphamap. Areas on an alphamap where the colour is darker is where the material will appear less transparent. Where the alphamap is lighter the material will be more transparent.

The example I have provided is simple but it explains all the processes you need to go through to get the correct results.

Here we have a standard square composed of two triangles; on it is a texture of a monkey's face. What I want to do with it is make it semi-transparent, about 50% transparent. This is perhaps the easiest kind of transparency to achieve. So here are the steps I followed to gain this degree of transparency.

1. When you have the texture applied to the face, load the texture into a paint program such as Photoshop or Paint Shop Pro (I have used Photoshop).

2. We need to create the alphamap from this texture so what we do is inverse the colours. To do this in Photoshop, click on Image->Adjust->Levels. The levels box will appear. What we want to do is move the sliders on the gradient bar at the bottom to either end, swapping them around. When this is done (your picture should now look sickening) click 'OK'. This effect can also be achieved by clicking Image->Adjust->Invert, or Ctrl+I.

3. You should now have an inverted colour map (shown below) which you can use as an alphamap for your model. So save the inverted texture somewhere (preferably in the same directory as your model). Optionally (to reduce memory usage) you can then make the image grayscale by clicking Image->Mode->Grayscale. (I usually leave the image with inverted colours because a truly inverted colour without loss of colour information gives true ratio transparency; in this case 50-50).

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4. Go into MilkShape 3D and click the alphamap button on the Materials tab in the Toolbox. Browse for your texture and open it once you have located it.

The alphamap should now be applied and you should see the difference in your 3D viewport (of not select the group the material is to be applied to and click apply in the materials tab.

This applied a 50-50 transparency (50% foreground texture - 50% background). To achieve variations on this you can darken and lighten the alphamap in your chosen paint package. In Photoshop use the Levels window as mentioned before, and slide the slider on the white gradient side closer to the darker side to get a less transparent alphamap. Slide the slider on the dark side closer to the light side to get a more transparent alphamap. Alternatively you can use the Transparency slider below the Emmisive button on the Toolbox: Model panel, however this tends to oversaturate the final material.