Gambas Documentation - /comp/gb.opengl/gl/frontface

# Gl.FrontFace (gb.opengl)

Static Sub FrontFace ( Mode As Integer )

Define front- and back-facing polygons.

### Parameters

mode

  Specifies the orientation of front-facing polygons. Gl.CW and Gl.CCW are accepted. The initial value is Gl.CCW.

### Description

In a scene composed entirely of opaque closed surfaces, back-facing polygons are never visible. Eliminating these invisible polygons has the obvious benefit of speeding up the rendering of the image. To enable and disable elimination of back-facing polygons, call Gl.Enable and Gl.Disable with argument Gl.CULL_FACE.

The projection of a polygon to window coordinates is said to have clockwise winding if an imaginary object following the path from its first vertex, its second vertex, and so on, to its last vertex, and finally back to its first vertex, moves in a clockwise direction about the interior of the polygon. The polygon's winding is said to be counterclockwise if the imaginary object following the same path moves in a counterclockwise direction about the interior of the polygon. Gl.FrontFace specifies whether polygons with clockwise winding in window coordinates, or counterclockwise winding in window coordinates, are taken to be front-facing. Passing Gl.CCW to mode selects counterclockwise polygons as front-facing; Gl.CW selects clockwise polygons as front-facing. By default, counterclockwise polygons are taken to be front-facing.

### Errors

Gl.INVALID_ENUM is generated if mode is not an accepted value.

### Associated Gets

Gl.Get with argument Gl.FRONT_FACE

### See also

- Gl.CullFace,

See original documentation on OpenGL website