#pragma once
#include "RenderTechnique.h"

/**
	@brief Base abstract class __declspec( dllexport ) of rendering a hierarchical particle system.

	A hierarchical particle system is a particle system made out of a smaller particle system. 
	It renders an image of the smaller particle system and multiplies this image to achieve a bigger particle system.
	This way fewer computation is needed to simulate large number of particles, while the trick is usually unnoticable.
*/
class __declspec( dllexport ) HierarchicalParticleSystemTechnique : virtual public RenderTechnique
{
public:
	/**
		@brief Constructor.

		@param startFrame				adds an offset to the current frame number to help evenly distribute updates between frames
		@param impostorUpdateInterval	update frequency of the impostor texture (image of the smaller system)
		@param impostorResolution		resolution of the impostor texture
		@param useDistCalc				flag to skip impostor update if object is far away (//not used)
		@param perspectiveRendering		sets if the impostor should be rendered with a perspective projection or orthogonal
		@param parentRenderable			the object to operate on
		@param parentTechniqueGroup		the TechniqueGroup this RenderedTechnique is attached to
	*/
	HierarchicalParticleSystemTechnique(
							unsigned long startFrame,
							unsigned long impostorUpdateInterval,
							unsigned int impostorResolution,
							bool useDistCalc,
							bool perspectiveRendering,
							ElementaryRenderable* parentRenderable,
							TechniqueGroup* parentTechniqueGroup
							);
	virtual ~HierarchicalParticleSystemTechnique();

	//inherited
	void update(unsigned long frameNum);
	//inherited
	void runChanged(RenderingRunType runType, RenderingRun* run);
	//inherited
	void runUpdated(RenderingRunType runType, RenderingRun* run);

protected:
	/**
			@brief update frequency of the impostor texture (image of the smaller system)
	*/
	unsigned long impostorUpdateInterval;
	/**
			@brief resolution of the impostor texture
	*/
	unsigned int impostorResolution;
	/**
			@brief offset in frame number used during update
	*/
	unsigned long startFrame;	
	/**
			@brief flag to skip impostor update if object is far away (//not used)
	*/
	bool useDistCalc;
	/**
			@brief sets if the impostor should be rendered with a perspective projection or orthogonal
	*/
	bool perspectiveRendering;
	/**
			@brief Creates the ChildParticleSystemRenderingRun needed by this technique.

			@return pointer to the ChildParticleSystemRenderingRun created instance
	*/
	virtual RenderingRun* createChildPSysRenderingRun()=0;	
	/**
			@brief Called if the impostor rendering run changed.

			@param run pointer to the new ChildParticleSystemRenderingRun instance to use
	*/
	virtual void impostorChanged(RenderingRun* run) = 0;
	/**
			@brief Called if the impostor rendering run is updated.

			@param run pointer to the updated ChildParticleSystemRenderingRu.
	*/
	virtual void impostorUpdated(RenderingRun* run) = 0;
	
};