// This file may be redistributed and modified only under the terms of
// the GNU General Public License (See COPYING for details).
// Copyright (C) 2003 Alistair Riddoch

#ifndef MERCATOR_FILL_DEPTH_SHADER_H
#define MERCATOR_FILL_DEPTH_SHADER_H

#include "Shader.h"

namespace Mercator {

/// \brief Shader to give the appearance of deep murky water.
///
/// Areas of terrain covered by water should be darker as less
/// distinct as they get deeper. This shader adds a uniform alpha blended
/// surface below water level which becomes more opaque as it gets deeper
/// concealing the underlying appearance of the terrain from a viewer
/// at the surface.
class DepthShader : public Shader {
private:
	/// The level of the surface of the water.
	float m_waterLevel;
	/// The depth at which the bottom becomes completely obscured.
	float m_murkyDepth;
public:
	/// Key string used when specifying the water level parameter.
	static const std::string key_waterLevel;
	/// Key string used when specifying the murky depth parameter.
	static const std::string key_murkyDepth;

	/// Default level of the surface of the water.
	static const float default_waterLevel;
	/// Default depth at which the bottom becomes completely obscured.
	static const float default_murkyDepth;

	/// \brief Constructor
	///
	/// @param waterLevel level of the surface of the water.
	/// @param murkyDepth depth at which the bottom becomes completely obscured.
	explicit DepthShader(float waterLevel = default_waterLevel,
						 float murkyDepth = default_murkyDepth);

	/// \brief Constructor
	///
	/// @param params a map of parameters for the shader.
	explicit DepthShader(const Parameters& params);

	~DepthShader() override;

	/// Accessor for the level of the surface of the water.
	float waterLevel() const { return m_waterLevel; }

	/// Accessor for the depth at which the bottom becomes completely obscured.
	float murkyDepth() const { return m_murkyDepth; }

	bool checkIntersect(const Segment&) const override;

	void shade(Surface&) const override;
};

} // namespace Mercator

#endif // MERCATOR_FILL_DEPTH_SHADER_H
