// ----------------------------------------------------------------

// From Game Programming in C++ by Sanjay Madhav

// Copyright (C) 2017 Sanjay Madhav. All rights reserved.

//

// Released under the BSD License

// See LICENSE in root directory for full details.

// ----------------------------------------------------------------

#include "SplineCamera.h"

#include "Actor.h"

Vector3 Spline::Compute(size_t startIdx, float t) const

{

// Check if startIdx is out of bounds

if (startIdx >= mControlPoints.size())

{

return mControlPoints.back();

}

else if (startIdx == 0)

{

return mControlPoints[startIdx];

}

else if (startIdx + 2 >= mControlPoints.size())

{

return mControlPoints[startIdx];

}

// Get p0 through p3

Vector3 p0 = mControlPoints[startIdx - 1];

Vector3 p1 = mControlPoints[startIdx];

Vector3 p2 = mControlPoints[startIdx + 1];

Vector3 p3 = mControlPoints[startIdx + 2];

// Compute position according to Catmull-Rom equation

Vector3 position = 0.5f * ((2.0f * p1) + (-1.0f * p0 + p2) * t +

(2.0f * p0 - 5.0f * p1 + 4.0f * p2 - p3) * t * t +

(-1.0f * p0 + 3.0f * p1 - 3.0f * p2 + p3) * t * t * t);

return position;

}

SplineCamera::SplineCamera(Actor* owner)

:CameraComponent(owner)

,mIndex(1)

,mT(0.0f)

,mSpeed(0.5f)

,mPaused(true)

{

}

void SplineCamera::Update(float deltaTime)

{

CameraComponent::Update(deltaTime);

// Update t value

if (!mPaused)

{

mT += mSpeed * deltaTime;

// Advance to the next control point if needed.

// This assumes speed isn't so fast that you jump past

// multiple control points in one frame.

if (mT >= 1.0f)

{

// Make sure we have enough points to advance the path

if (mIndex < mPath.GetNumPoints() - 3)

{

mIndex++;

mT = mT - 1.0f;

}

else

{

// Path's done, so pause

mPaused = true;

}

}

}

// Camera position is the spline at the current t/index

Vector3 cameraPos = mPath.Compute(mIndex, mT);

// Target point is just a small delta ahead on the spline

Vector3 target = mPath.Compute(mIndex, mT + 0.01f);

// Assume spline doesn't flip upside-down

const Vector3 up = Vector3::UnitZ;

Matrix4 view = Matrix4::CreateLookAt(cameraPos, target, up);

SetViewMatrix(view);

}

void SplineCamera::Restart()

{

mIndex = 1;

mT = 0.0f;

mPaused = false;

}