HP Workstation zx2000 OpenGL 1.1 Reference for HP-UX 11.x - Page 109

Chapter 4 D glDisable This token enables HP's occlusion-testing extension. If any geometry is rendered while occlusion culling is enabled, and if that geometry would be visible (i.e., rendering it would affect the Z-buffer), the occlusion test state bit is set, indicating that the rendered object is visible. This is typically done to increase performance: if every pixel of a bounding box would be "behind" the current Z-buffer values for those pixels (i.e., the bounding box is entirely occluded), anything you would draw within that bounding box would also be behind the current Z values, and therefore you can cull it (i.e., avoid processing that geometry through the pipeline). Note that this enable has no effect on the current render mode, or any other OpenGL state. GL_POINT_SMOOTH If enabled, draw points with proper filtering. Otherwise, draw aliased points. See glPointSize. GL_POLYGON_OFFSET_FILL If enabled, and if the polygon is rendered in GL_FILL mode, an offset is added to depth values of a polygon's fragments before the depth comparison is performed. See glPolygonOffset. GL_POLYGON_OFFSET_LINE If enabled, and if the polygon is rendered in GL_LINE mode, an offset is added to depth values of a polygon's fragments before the depth comparison is performed. See glPolygonOffset. GL_POLYGON_OFFSET_POINT If enabled, an offset is added to depth values of a polygon's fragments before the depth comparison is performed, if the polygon is rendered in GL_POINT mode. See glPolygonOffset. GL_POLYGON_SMOOTH If enabled, draw polygons with proper filtering. Otherwise, draw aliased polygons. For correct anti-aliased polygons, an alpha buffer is needed and the polygons must be sorted front to back. GL_POLYGON_STIPPLE If enabled, use the current polygon stipple pattern when rendering polygons. See glPolygonStipple. GL_RESCALE_NORMAL_EXT When normal rescaling is enabled, a new operation is added to the transformation of the normal vector into eye coordinates. The normal vector is rescaled after it is multiplied by the inverse modelview matrix and before it is normalized. The rescale factor is chosen so that in many cases normal vectors with unit length in object coordinates will not need to be normalized as they are transformed into eye coordinates. GL_SCISSOR_TEST If enabled, discard fragments that are outside the scissor rectangle. See glScissor. GL_STENCIL_TEST If enabled, do stencil testing and update the stencil buffer. See glStencilFunc and glStencilOp. GL_TEXTURE_1D 109