Native bindings to the OES_viewport_array extension.

OpenGL ES is modeled on a pipeline of operations. The final stage in this pipeline before rasterization is the viewport transformation. This stage transforms vertices from view space into window coordinates and allows the application to specify a rectangular region of screen space into which OpenGL ES should draw primitives. Unextended OpenGL ES implementations provide a single viewport per context. In order to draw primitives into multiple viewports, the OpenGL ES viewport may be changed between several draw calls. With the advent of Geometry Shaders, it has become possible for an application to amplify geometry and produce multiple output primitives for each primitive input to the Geometry Shader. It is possible to direct these primitives to render into a selected render target. However, all render targets share the same, global OpenGL ES viewport.

This extension enhances OpenGL ES by providing a mechanism to expose multiple viewports. Each viewport is specified as a rectangle. The destination viewport may be selected per-primitive by the geometry shader. This allows the Geometry Shader to produce different versions of primitives destined for separate viewport rectangles on the same surface. Additionally, when combined with multiple framebuffer attachments, it allows a different viewport rectangle to be selected for each. This extension also exposes a separate scissor rectangle for each viewport. Finally, the viewport bounds are now floating point quantities allowing fractional pixel offsets to be applied during the viewport transform.

Requires GLES32, EXT_geometry_shader or OES_geometry_shader.