More About Opacity Mapping

This article was written by Polystyrene!

Opacity maps are used to tell Create Mode which parts of your product you want to be seen and which you want to be invisible – it basically cuts out parts of the texture.

The Rules:

  • Your opacity map must be the exact same size as your texture map
  • Black = invisible/shows skin
  • White = what is seen
  • Grey = sheer (darker grey = more clear; lighter grey = more solid)
  • Only use blending if your product has sheer/ semi see-through parts. This is because of blending clashing – if you have a blended material in front of another blended material, it often causes one of them to disappear. This is why your avi sometimes goes bald when you stand it behind windows. So it’s best to leave blending turned off whenever possible.Example 1 – Clothing

Example 1 – Clothing

For this example, let’s make a skintight tank top. We’ll derive from a skintight top, such as this one. This top covers all of the upper body and arms, so to turn it into a tank top we need to use an opacity map to cut out the parts we don’t need.

First of all, here is a guide to show you which bits of the template correspond to which bits of the body. This 256×512 template is used for most skintights – it wraps around the body of the avatar.

Now, for our tank top we want the “fabric” to cover these parts:

So, for our opacity map we make the parts we want to see white and the parts we want to be invisible black:

To put the opacity map into Create Mode, go to the Materials section in the Meshes tab. You can see where the texture and opacity maps go. Click the Edit button over the opacity map slot, choose your opacity map, then click Open. To add your texture click on the Edit button over the texture slot, choose your texture map, then click Open.

Click “Apply Changes” and you’ll see that your opacity map has changed the skintight top into a tank top!

Example 2 – Backdrop Furniture

For this example we’ll make a backdrop/enhancer. Derive from a flat plane, such as this one. This product is basically a wall, which uses an opacity map to cut parts out and turn it into something!

Say we want to create a word plane with the word “Hello!”, we’ll make an opacity map with the word in white and the rest black:

If we want to make the word red we can use a red texture map the exact same size as the opacity map:

Put in the opacity map and texture map just like in the first example. Make sure that blending is turned off by unchecking the Use blending tick box;

Click “Apply Changes” and you’ll get a floating “Hello!”
Now say that we want to make something a bit more fancy – we will add a flame effect to the opacity map. Because we want this effect to be semi see-through, we use shades of grey:

Put the new opacity map into Create Mode. And this time we want blending to be turned on, so that we can see the semi see-through parts:

Click “Apply Changes” and you’ll get the floating “Hello!” with a flame effect:

A note about ‘Blending Mode’

Under the drop down menu you can change the settings for Blending Mode. Most of the time when we need blending we will be using ‘Composite’ – this simply makes the texture transparent (for example, the lenses in a pair of glasses).

The other setting is ‘Additive’ – Additive blending literally takes the texture and “adds” light values to it based on values in your opacity map. The more additive textures you have in front of one another, the brighter and brighter they get. This is handy for things like shafts of light.

These are all very basic examples, but opacity map can be used to create all sorts of products, from simple shapes to complex designs – just play around and use your imagination!

Have fun!

Updated on July 21, 2023

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