#include "defines.h"

#include "Water.h"

#include "shader.h"
#include "globals.h"

#include "intrin.h"

void Water::Init()
{
}

void Water::Update(const D3DXMATRIX &mView, const D3DXMATRIX &mProj)
{
	// Mirror reflection
	D3DXMATRIX mMirror;
	D3DXMatrixIdentity(&mMirror);
	mMirror._22 = -1.0f;
	mMirror._42 = 2.0f * m_fWaterLevel;
	m_ViewMatrix = mMirror * mView;

	// Extract new view position
	m_ViewPos.x = -(m_ViewMatrix._41 * m_ViewMatrix._11 + m_ViewMatrix._42 * m_ViewMatrix._12 + m_ViewMatrix._43 * m_ViewMatrix._13);
	m_ViewPos.y = -(m_ViewMatrix._41 * m_ViewMatrix._21 + m_ViewMatrix._42 * m_ViewMatrix._22 + m_ViewMatrix._43 * m_ViewMatrix._23);
	m_ViewPos.z = -(m_ViewMatrix._41 * m_ViewMatrix._31 + m_ViewMatrix._42 * m_ViewMatrix._32 + m_ViewMatrix._43 * m_ViewMatrix._33);

	// Extract camera direction
	m_ViewDir.x = m_ViewMatrix._13;
	m_ViewDir.y = m_ViewMatrix._23;
	m_ViewDir.z = m_ViewMatrix._33;

	float fEyeHeight = -(mView._41 * mView._21 + mView._42 * mView._22 + mView._43 * mView._23);

	float fReflectionClipHeight = m_fWaterLevel
		- min(max(fEyeHeight - m_fWaterLevel, 0.0f), 64.0f) / 32.0f;

	// Clip reflection
	m_ProjMatrix = ObliqueProjectionMatrix(m_ViewMatrix, mProj,
		D3DXPLANE(0.0f, -1.0f, 0.0f, fReflectionClipHeight));
}

/// Returns the sign of the given value
inline float Sign0(float v)
{
	return (v > 0.0f) ? 1.0f : ((v < 0.0f) ? -1.0f : 0.0f);
}

// Computes a projection matrix that contains the given plane as near plane
D3DXMATRIX Water::ObliqueProjectionMatrix(const D3DXMATRIX &mView, const D3DXMATRIX &mProjection, const D3DXPLANE &clipPlane)
{
	// Compute inverse transpose (orthogonal matrix)
	D3DXMATRIX mViewInverseTranspose = mView;
	mViewInverseTranspose._14 = -(mView._41 * mView._11 + mView._42 * mView._12 + mView._43 * mView._13);
	mViewInverseTranspose._24 = -(mView._41 * mView._21 + mView._42 * mView._22 + mView._43 * mView._23);
	mViewInverseTranspose._34 = -(mView._41 * mView._31 + mView._42 * mView._32 + mView._43 * mView._33);
	mViewInverseTranspose._41 = mView._14;
	mViewInverseTranspose._42 = mView._24;
	mViewInverseTranspose._43 = mView._34;
	
	// Transform plane to view space
	D3DXPLANE viewClipPlane = -clipPlane;
	D3DXPlaneTransform(&viewClipPlane, &viewClipPlane, &mViewInverseTranspose);

	// Check clip plane orientation
	if(viewClipPlane.d > -0.001f)
		return mProjection;

	// Compute view-space corner point
	D3DXVECTOR4 vFarCorner = D3DXVECTOR4(
		Sign0(viewClipPlane.a + mProjection._31) / mProjection._11,
		Sign0(viewClipPlane.b + mProjection._32) / mProjection._22,
		-1.0f,
		(1.0f + mProjection._33) / mProjection._43 );
	
	// Scale clip plane
	D3DXPLANE projClipPlane = viewClipPlane * (1.0f / D3DXPlaneDot(&viewClipPlane, &vFarCorner));

	// Modify projection matrix
	return D3DXMATRIX(mProjection._11, mProjection._12, projClipPlane.a, mProjection._14,
		mProjection._21, mProjection._22, projClipPlane.b, mProjection._24,
		mProjection._31, mProjection._32, projClipPlane.c, mProjection._34,
		mProjection._41, mProjection._42, projClipPlane.d, mProjection._44);
}