After clipping and division by w, depth coordinates range from -1 to 1, corresponding to the near and far clipping planes. depthRange specifies a linear mapping of the normalized depth coordinates in this range to window depth coordinates. Regardless of the actual depth buffer implementation, window coordinate depth values are treated as though they range from 0 through 1 (like color components). Thus, the values accepted by depthRange are both clamped to this range before they are accepted.

The initial setting of (0, 1) maps the near plane to 0 and the far plane to 1. With this mapping, the depth buffer range is fully utilized.

It is not necessary that the near value be less than the far value. Reverse mappings such as (1, 0) are acceptable.

A 2-dimensional position, measured in pixels.

A 2-dimensional size, measured in pixels.

Controls the affine transformation from normalized device coordinates to window coordinates. The viewport state variable consists of the coordinates (x, y) of the lower left corner of the viewport rectangle, (in pixels, initial value (0,0)), and the size (width, height) of the viewport. When a GL context is first attached to a window, width and height are set to the dimensions of that window.

Let (xnd, ynd) be normalized device coordinates. Then the window coordinates (xw, yw) are computed as follows:

xw = (xnd + 1) (width / 2) + x

yw = (ynd + 1) (heigth / 2) + y

Viewport width and height are silently clamped to a range that depends on the implementation, see maxViewportDims.

The implementation-dependent maximum viewport width and height.

A matrix stack.

Controls which matrix stack is the target for subsequent matrix operations. The initial value is (Modelview 0).

Push the current matrix stack down by one, duplicating the current matrix, excute the given action, and pop the current matrix stack, replacing the current matrix with the one below it on the stack (i.e. restoring it to its previous state). The returned value is that of the given action. Note that a round-trip to the server is probably required. For a more efficient version, see unsafePreservingMatrix.

A more efficient, but potentially dangerous version of preservingMatrix: The given action is not allowed to throw an exception or change the current matrix mode permanently.

If rescaleNormal contains Enabled, normal vectors specified with normal are scaled by a scaling factor derived from the modelview matrix. rescaleNormal requires that the originally specified normals were of unit length, and that the modelview matrix contains only uniform scales for proper results. The initial value of rescaleNormal is Disabled.

If normalize contains Enabled, normal vectors specified with normal are scaled to unit length after transformation. The initial value of normalize is Disabled.