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

# Gl.ClipPlane (gb.opengl)

Static Sub ClipPlane ( Plane As Integer, Equation As Float[] )

Specify a plane against which all geometry is clipped.

### Parameters

plane

  Specifies which clipping plane is being positioned. Symbolic names of the form Gl.CLIP_PLANEi, where i is an integer between 0 and Gl.MAX_CLIP_PLANES -1 , are accepted.

equation

  Specifies the address of an array of four double-precision floating-point values. These values are interpreted as a plane equation.

### Description

Geometry is always clipped against the boundaries of a six-plane frustum in x, y, and z. Gl.ClipPlane allows the specification of additional planes, not necessarily perpendicular to the x, y, or z axis, against which all geometry is clipped. To determine the maximum number of additional clipping planes, call Gl.GetIntegerv with argument Gl.MAX_CLIP_PLANES. All implementations support at least six such clipping planes. Because the resulting clipping region is the intersection of the defined half-spaces, it is always convex.

Gl.ClipPlane specifies a half-space using a four-component plane equation. When Gl.ClipPlane is called, equation is transformed by the inverse of the modelview matrix and stored in the resulting eye coordinates. Subsequent changes to the modelview matrix have no effect on the stored plane-equation components. If the dot product of the eye coordinates of a vertex with the stored plane equation components is positive or zero, the vertex is in with respect to that clipping plane. Otherwise, it is out.

To enable and disable clipping planes, call Gl.Enable and Gl.Disable with the argument Gl.CLIP_PLANEi, where i is the plane number.

All clipping planes are initially defined as (0, 0, 0, 0) in eye coordinates and are disabled.

### Notes

It is always the case that Gl.CLIP_PLANE i = Gl.CLIP_PLANE0 + i.

### Errors

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

Gl.INVALID_OPERATION is generated if Gl.ClipPlane is executed between the execution of Gl.Begin and the corresponding execution of Gl.End.

### Associated Gets

Gl.GetClipPlane

Gl.IsEnabled with argument Gl.CLIP_PLANEi

### See also

- Gl.Enable

See original documentation on OpenGL website