/*****************************************************************************************
*                                                                                       *
* OpenSpace                                                                             *
*                                                                                       *
* Copyright (c) 2014-2016                                                               *
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* or substantial portions of the Software.                                              *
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#include <modules/globebrowsing/rendering/frustrumculler.h>

namespace {
	const std::string _loggerCat = "FrustrumCuller";
}

namespace openspace {

	//////////////////////////////////////////////////////////////////////////////////////
	//							PATCH RENDERER											//
	//////////////////////////////////////////////////////////////////////////////////////
	FrustrumCuller::FrustrumCuller()
	{

	}

	FrustrumCuller::~FrustrumCuller() {
		
	}


	bool FrustrumCuller::isVisible(const RenderData& data, const vec3& point, const glm::vec2& marginScreenSpace) {

		mat4 modelTransform = translate(mat4(1), data.position.vec3());
		mat4 viewTransform = data.camera.combinedViewMatrix();
		mat4 modelViewProjectionTransform = data.camera.projectionMatrix()
			* viewTransform * modelTransform;

		vec2 pointScreenSpace = transformToScreenSpace(point, modelViewProjectionTransform);
		return testPoint(pointScreenSpace, marginScreenSpace);
	}


	bool FrustrumCuller::isVisible(const RenderData& data, const LatLonPatch& patch, double radius) {
		// An axis aligned bounding box based on the patch's minimum boudning sphere is
		// used for testnig
	
		// Calculate the MVP matrix
		mat4 modelTransform = translate(mat4(1), data.position.vec3());
		mat4 viewTransform = data.camera.combinedViewMatrix();
		mat4 modelViewProjectionTransform = data.camera.projectionMatrix()
			* viewTransform * modelTransform;

		// Calculate the patch's center point in screen space
		vec4 patchCenterModelSpace = vec4(radius * patch.center().asUnitCartesian(), 1);
		vec4 patchCenterProjectionSpace = modelViewProjectionTransform * patchCenterModelSpace;
		vec2 pointScreenSpace = (1.0f / patchCenterProjectionSpace.w) * patchCenterProjectionSpace.xy;
		
		// Calculate the screen space margin that represents an axis aligned bounding 
		// box based on the patch's minimum boudning sphere
		double boundingRadius = radius * patch.minimalBoundingRadius();
		vec4 marginProjectionSpace = vec4(vec3(boundingRadius), 0) * data.camera.projectionMatrix();
		vec2 marginScreenSpace = (1.0f / patchCenterProjectionSpace.w) * marginProjectionSpace.xy;

		// Test the bounding box by testing the center point and the corresponding margin
		return testPoint(pointScreenSpace, marginScreenSpace);
	}





	bool FrustrumCuller::testPoint(const glm::vec2& pointScreenSpace,
		const glm::vec2& marginScreenSpace) const 
	{
		
		const vec2& p = pointScreenSpace;

		vec2 cullBounds = vec2(1) + marginScreenSpace;
		return ((-cullBounds.x < p.x && p.x < cullBounds.x) &&
				(-cullBounds.y < p.y && p.y < cullBounds.y));
	}


	glm::vec2 FrustrumCuller::transformToScreenSpace(const vec3& point, 
		const mat4x4& modelViewProjection) const 
	{
		vec4 pointProjectionSpace = modelViewProjection * vec4(point, 1.0f);
		vec2 pointScreenSpace = (1.0f / pointProjectionSpace.w) * pointProjectionSpace.xy;
		return pointScreenSpace;
	}


}  // namespace openspace