# Blender 3D: Noob to Pro/Using a texture to make a material partially transparent

|previous=Using Textures
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To understand the collaboration of textures and material we will use the
opacity of a material - the alpha value - as an example. We will show
how to set the opacity/transparency of a material with different types
of textures.

The Alpha value of the material is set with the *A*(lpha) slider in the
Material panel. This is the basic Alpha value. If *Alpha* is 1, the
material is fully opaque, if *Alpha* is 0, the material is fully
transparent.

Now you change that basic Alpha value with a texture.

1.  If the basic Alpha value is 1 you can only lower it with a texture,
    because 1 is the maximum value anyway.
2.  If the basic Alpha value is 0 you can only increase it with a
    texture.

The target value of Alpha that can be achieved with the texture is set
with the **DVar** button in the *Map To* panel. If *Alpha* is 0 and
*DVar* is 0 than nothing will happen. You can set either:

1.  *Alpha* to 1 and *DVar* to 0, then the texture will lower the Alpha
    value, or you can set
2.  *Alpha* to 0 and *DVar* to 1, then the texture will increase the
    Alpha value.

Both methods are possible and equal in the result, but for clarity we
will always use method number 1. There are more combinations possible,
so it may be that you find tutorials with different settings.

## Using a greyscale texture - white for opaque

!**Image 1a:** Greyscale Image of
leaf{width="200"}
In **Img. 1a** the black areas shall become transparent, the white areas
shall become opaque.

-   Load the image as *Image* texture, turn off *Use Alpha*.
-   Set the *Alpha* value in the material buttons to 1. This is the
    default value anyway.
-   Activate *ZTransp* (or *RayTransp* if you need refraction)
-   The *Map To* panel:
    -   Turn off *Col* (or else the texture would also affect the color
        of the material)
    -   Turn on *Alpha* inverse, you have to click it twice. We need
        inverse here, because the texture shall affect the material from
        its black parts. (**Noob Note**: *On blender 2.63 you need to
        set a specific \'Alpha\' value (the one located under
        \'influence-\>diffuse) to -1, as the alpha button referenced in
        this step no longer exists in 2.63.*)
    -   Turn on *Spec* inverse (you don\'t want your transparent
        sections to show specular highlights) (**Noob Note**: *As far as
        I could tell, the equivalent to doing this on blender 2.63 is to
        set a specific \'Intensity\' value (located under
        Influence-\>Specular) to -1.*)
    -   Set the *DVar* value to 0. The default value is 1.

framed\|**Image 1b:** Material settings for the
texture Now
let\'s take a look at the texture.

-   Where the texture has a value of 0 (e.g. black) it will affect the
    Map To values fully (because we have used inverse).
-   Where the texture has a value of 1 (e.g. white) it will do nothing.
-   Where the texture has a value in between 0 and 1 it will affect the
    Map To values partially.

!**Image 1c:** Result of applying the Greyscale Image to a
plane{width="200"}
The result is shown in **Img. 1c**, the texture applied to a plane
rendered against a white world background.

If your texture is inverted, i.e. black shall become opaque and white
transparent, simply use the normal *Alpha* and *Spec* setting in the
*Map To* panel. (**Noob Note** *If you don\'t see the white \'shine\' on
the maple leaf, move the default point lamp (lighting source) closer to
the plane mesh to which the texture and material are assigned.*)

That\'s it. It\'s basically the same for all settings, the only problem
that remains is sometimes to know which value a texture will give if you
use transparent textures or colored textures. 

**_For 2.7 blenderers out there:_** To obtain the
results I had a hard time and finally came across (almost accidentally)
to uncheck the \'use alpha\' button in the image sub panel of the
texture menu. Then, you can get the results as above.

## Using a partially transparent texture to make the material transparent

!**Image 2a:** Using a partially transparent
texture{width="200"}
Often we have a partially transparent texture, and want to directly use
that transparency of the texture to make the material transparent too.
We have now to think a bit about the values that are generated by the
texture itself: If we load the image texture with *Use Alpha*, the Alpha
value of the image is used as input value for *Alpha* and *Spec* in the
*Map To* panel. So a fully transparent pixel in the image has an Alpha
value of 0, a fully opaque pixel has an Alpha value of 1. This is
exactly the same situation as above, simply turning on *Use Alpha* and
*Premul*(tiply Alpha in Advance) will give use the same result as with
the greyscale image.  framed\|**Image 2b:**
Texture settings for a RGB/Alpha
texture So:

-   Turn on *Use Alpha* in the *Map Image* panel of the texture buttons.
-   Turn on *Premul* in the *Image* panel. This is necessary to get real
    partial transparent borders.
-   Turn on *Col* in the *Map To* panel additionally.

!**Image 2c:** The
result{width="200"}
The rendering result is pretty similar to **Img. 2a**, only that it is
affected by lighting (and casts shadows).

Don\'t forget to turn on *TraShadow* in the *Shaders* panel for the
object that is **receiving** the shadow. (**Noob Note:** In Blender 2.6x
you also need to check the \"Receive Transparent\" box in the shadow
section of the material for the object receiving shadows or you will get
a black square shadow.)

(**Noob Note:** *In this case add a plane colored white just below the
\"leaf.\" This is the object the you should turn on* **TraShadow** *with
as this is the object that will receive the shadow. This is also
providing that you have a light source properly positioned.*)
 
