Order-Independent Transparency

Order-independent transparency \(OIT\) corrects the display of transparent objects that are drawn out of order.

OIT is useful when creating the following:

Concave geometry – When you create concave geometry, such as a glass, wine glass, or glass sculpture, some triangles may cover the same pixels and are drawn on top of each other. OIT solves the out-of-order issues that appear from certain angles.
Intersecting geometry – When you create intersecting geometry, such as hair planes, some triangles may intersect in separate draws. OIT properly orders the triangles for each pixel.
Transparent objects inside transparent objects – This includes liquids inside of glasses, holograms, or x-ray style effects.

To further demonstrate, see the following images.


OIT is not needed in the following example. Drawing object 1, then object 2, and finally object 3 works.	OIT is needed in the following example. Drawing object 1 and then object 2 will not work because certain pixels from object 1 must be in front of pixels from object 2 \(and vice versa\).	OIT is needed in the following example. Object 2 is long and its center point is in front of object 1, but it must draw behind object 1.	OIT is needed in the following example. Certain parts of object 1 draw behind other parts of the object, and you cannot control which draws first.

Configuring Order-Independent Transparency for Lumberyard

You can configure OIT with the console or create a level configuration file with this setting.

Specify the value for r_AlphaBlendLayerCount to the number of transparency layers that OIT can solve. A value of 1 is sufficient to solve most out-of-order transparency issues.

Valid values: 0 – 4

0 = Disables OIT

Specify the value for the r_AlphaBlendLayerCount console variable
Specify the value for the level.cfg file in the lumberyard_version\dev\project_name\Levels\level_name directory.

For more information, see Configuring Console Variables.

OIT requires the following:

Hardware requirements: DirectX 12_1 feature level compatible graphics card \(NVIDIA Maxwell & Pascal, 4th generation Intel core processors\).
Software requirements: DirectX 11.3 and 12 runtime on Windows 10 compiled with Windows 10 SDK.

To set the Windows 10 SDK for Lumberyard

With a text editor, open the user_settings.options file in the lumberyard_version\dev\_WAF_ directory.
Under the [Windows Options] section, set win_vs2017_winkit to your version of the Windows 10 SDK \(for example, *10\.1\.17134\.12*\).
Build your game project. For more information, see Building Lumberyard projects.