/**
 * \file fog.h
 * Fog operations.
 * 
 * \if subset
 * (No-op)
 *
 * \endif
 */

/*
 * Mesa 3-D graphics library
 *
 * Copyright (C) 1999-2001  Brian Paul   All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */


#ifndef FOG_H
#define FOG_H


#include "util/glheader.h"

struct gl_context;

extern void _mesa_init_fog( struct gl_context * ctx );

/**
 * The fixed-function vertex program stores the *signed* eye-space Z in
 * gl_FogFragCoord and defers the abs() of the GL_EYE_PLANE_ABSOLUTE_NV
 * distance mode to the fragment stage, so that it is applied per fragment
 * rather than baked into the interpolated per-vertex value (mesa #15407).
 *
 * Returns true when the fog coordinate reaching the fragment stage was
 * produced that way -- i.e. fixed-function vertex processing feeding the
 * GL_FRAGMENT_DEPTH / GL_EYE_PLANE_ABSOLUTE_NV fog coordinate -- meaning the
 * fragment stage must take abs() of gl_FogFragCoord.
 */
extern bool
_mesa_fog_coord_needs_deferred_abs(const struct gl_context *ctx);

#endif
