/* -*-c++-*- */
/* osgEarth - Geospatial SDK for OpenSceneGraph
* Copyright 2020 Pelican Mapping
* http://osgearth.org
*
* osgEarth is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* 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.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program.  If not, see <http://www.gnu.org/licenses/>
*/
#ifndef OSGEARTH_UTIL_LOG_DEPTH_BUFFER_H
#define OSGEARTH_UTIL_LOG_DEPTH_BUFFER_H  1

#include <osgEarth/Common>
#include <osg/Camera>

namespace osgEarth { namespace Util
{
    /**
     * Installs and controls a logarithmic depth buffer that improves
     * rendering of close and far objects in the same view without
     * z-fighting artifacts.
     *
     * Note: Only works with perspective projections. For an orthographic
     * projection it is a NOP.
     *
     * Note: If you have any RTT cameras that deal with depth data,
     * they need to use a log buffer as well! (e.g., ClampingTechnique)
     *
     * Another Note: For this to work properly, sufficient tessellation
     * of objects very close to the camera is necessary. Huge polygons
     * that intersect the near plane are likely to be clipped in their
     * entirely. Increasing the tessellation can resolve that issue.
     */
    class OSGEARTH_EXPORT LogarithmicDepthBuffer
    {
    public:
        /** Constructs a logarithmic depth buffer controller. */
        LogarithmicDepthBuffer();

        /**
         * Whether to write to gl_FragDepth. (default = true)
         * Pro: accurate clipping near the camera regardless of weak tessellation
         * Con: writes to gl_FragDepth defeats early-Z testing on the GPU (hurting
         *      performance in fill-limited scenarios)
         *
         * Set this before calling install().
         */
        void setUseFragDepth(bool value);
        bool getUseFragDepth() const { return _useFragDepth; }

        /** is it supported on this platform? */
        bool supported() const { return _supported; }

        /** Installs a logarithmic depth buffer on a camera. */
        void install(osg::Camera* camera);

        /** Uninstalls a logarithmic depth buffer from a camera. */
        void uninstall(osg::Camera* camera);

    protected:
        osg::ref_ptr<osg::NodeCallback> _cullCallback;
        bool _supported;
        bool _useFragDepth;
    };

} }

#endif // OSGEARTH_UTIL_LOG_DEPTH_BUFFER_H