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- [Narrator] Hi, this is the
last video of this section,

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Updating the Game Engine
to Use Thomas and Bob.

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In the previous video,

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we looked at building
Thomas and Bob classes.

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In this video, we'll be updating Engine.h,

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the input function, the update function,

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and also we'll draw Bob and Thomas.

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In order to be able to run the game

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and see our new characters,

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we have to declare instances of them,

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call their spawn functions,

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update them each frame
and draw them each frame.

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Let's start with declaring
their instances now.

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So, open up the Engine.h file

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and add the include directives first.

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#include "Thomas.h"

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#include "Bob.h"

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Now, inside private section,
after "TextureHolder th,"

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write a comment "//Thomas
and his friend , bob"

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then "Thomas m_Thomas;"

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and "Bob m_Bob;"

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So, we have an instance
of both Thomas and Bob

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which are derived from playable character.

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Now, we'll add the ability to
control the two characters.

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The code we'll add will
go in the input part.

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Of course, for this project,

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we have a dedicated input function.

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Open up "Input.cpp" and
add this highlighted code.

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Note that the code has
all the functionalities

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contained with Thomas and Bob classes.

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All the code has to do is
add an include directive

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for each of the Thomas and Bob classes.

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Then, within the input function,

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the code just calls the pure
virtual Handle input functions

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on m_Thomas and m_Bob.

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The reason we wrap each of
the calls in an "if" statement

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is because they return it
true or false based upon

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whether a new jump has just
been successfully initiated.

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We will handle playing
the jump sound effects

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in section four, Sound
Specialization and HUD.

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Let's move on to updating
the update function

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to spawn and update the
playable character instances.

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This is broken down into two parts.

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First, we need to spawn Bob and Thomas

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at the start of a new level.

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And second, we need to update

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by calling their update
functions each frame.

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We need to call the spawn
functions of our Thomas

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and Bob objects in a few different places

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as the project progresses.

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Most obviously, we need to
spawn the two characters

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when a new level begins.

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In this section, as the number
of tasks we need to perform

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at the beginning of a level increases,

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we will write a LoadLevel function.

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For now, lets just call spawn on m_Thomas

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and m_Bob in the update function,

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as seen in this highlighted code.

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Add the code but keep
in mind that this code

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will eventually be deleted and replaced.

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The entire code is wrapped
in an "if" statement

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that checks whether a
new level is required.

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Then this code simply calls
spawn and passes in a location

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in the game world along with the gravity.

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The actual spawning code will be moved

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to a dedicated LoadLevel
function but the "if" condition

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will be part of the finished project.

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Also, m_TimeRemaining is set
to an arbitrary 10 seconds.

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And here, we set
m_NewLevelRequired to false.

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Next, we update Thomas and Bob.

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So, inside the "if" loop
for condition m_Playing,

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add a comment, "//Update Thomas"

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then "m_Thomas.update(dtAsSeconds);."

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Similarly, "//Update Bob"

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"m_Bob.update(dtAsSeconds);"

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All we do here is call
their update functions

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and pass in the time this frame has taken.

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Now that the characters can move,

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we need to update the
appropriate view objects

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to center around the characters

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and make them the center of attention.

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Of course, until we have some
objects in our game world,

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the sensation of actual
movement will not be achieved.

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Add this highlighted code

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just after "End if playing" comment.

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The code handles the
two possible situations.

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First, the "if (m_SplitScreen)"
condition positions

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the left hand view around m_Thomas

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and here it positions the
right hand view around m_Bob.

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The "else" clause that executes

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when the game is in full screen mode

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tests to see if "m_Character1" is true.

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If it is, then the full
screen view "m_MainView"

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is centered around Thomas.

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Otherwise, in an "else" condition,

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it is centered around Bob.

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You probably remember that
the player can use the E key

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to toggle split screen mode
and the Q key to toggle

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between Bob and Thomas
in full screen mode.

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We coded this in the input
function of the Engine class

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back in the previous section,

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Abstraction and Code Management;
Making Better Use of OOP.

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Now, let's draw Bob and Thomas.

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Make sure the "Draw.cpp" file is open

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and then if not equal
to "m_SplitScreen" after

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"m_Window.setView" write a comment,

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"//Draw Thomas"

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"m_Window.draw(m_Thomas.getSprite ());"

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In the same way, draw Bob.

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"m_Window.draw(m_Bob.getSprite ());"

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Notice that we drew both Thomas
and Bob for the full screen.

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Now, we'll draw them for left and right.

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After "m_Window.setView" write comment,

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"//Draw bob"

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"m_Window.draw(m_Bob.getSprite());"

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Similarly, draw Thomas.

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"m_Window.draw(m_Thomas.getSprite());"

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Here, we have drawn Thomas
and Bob for left view.

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Now, note the very subtle
difference in the way

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that we draw the character
in split screen mode.

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When drawing the left side of the screen,

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we switch the order the
characters are drawn

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and draw Thomas after Bob.

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So, Thomas will always
be on top on the left

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and Bob on the right.

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This is because the player
controlling Thomas is catered for

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on the left and Bob on the right.

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You can run the game by clicking on

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"Local Windows Debugger" button.

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You can move Bob with
the help of arrow keys.

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See he moves towards left and right.

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If you press the Q key to
switch focus from Bob to Thomas,

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you can move Thomas using keys A and D.

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I'm moving Thomas to the left using key A

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and to the right using D key.

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If you move either of the
characters left or right,

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you will see them move
relative to each other.

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Now, try pressing the E key
to toggle between full screen

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and split screen.

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This is the split screen.

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Then try moving both characters
again to see the effect.

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You can see that Thomas is always centered

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in the left hand window

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and Bob is always centered
in the right hand window.

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If you leave the game running long enough,

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the characters will re-spawn

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in their original
positions every 10 seconds,

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as you can see here.

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This is the beginning of the
functionality we will need

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for the finish game.

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This behavior is cause by
"m_TimeRemaining" going below zero

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and then setting the

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"m_NewLevelRequired" variable to "true."

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Also note that we can't see
the full effect of movement

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until we draw the details of the level.

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In fact, although it can't be seen,

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both characters are continuously falling

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at 300 pixels per second.

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As the camera is centering
around them every frame

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and there are no other
objects in the game world,

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we cannot see this downward movement.

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If you want to demonstrate
this to yourself,

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in "Update.cpp" just change
the call to "m_Bob.spawn"

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Change this 100 to zero
and gravity to zero.

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Now that Bob has no gravitational effect,

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he'll move an upward direction.

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Thomas will visibly fall away from him.

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We will add some playable
levels to interact with

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in the next section.

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In this video, we've
update the game engine

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to use Thomas and Bob.

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Amazing!

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In this section,

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we started off by learning
inheritance and polymorphism.

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Then looked at abstract classes

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and building the playable character class.

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Lastly, we explored building
the Thomas and Bob classes

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and updating the game engine
to use Thomas and Bob.

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Awesome!

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In the next section, we'll learn

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"Building Playable Levels
and Collision Detection."