Homework 3: Define and Implement the Asciimation Class

In the previous parts, you saw the BoundingBox, Sprite and Display classes. Now it's time to put them together in the Asciimation class, which will manage the overall animation.

What the Asciimation Class Does

The job of the Asciimation twofold:

• It acts as a framebuffer, storing the content that needs to be shown on the display.
• It acts as a sprite manager, putting the content of one or more Sprite objects into the framebuffer at the right locations.

Your Task

Helpful Hints

Accessing a Static Member

You can access a class's static member variable using the class name and the scope-resolution operator; for example, ClassName::variableName.

Initializing the Sprite

Remember that the default constructor for the Sprite class is disabled! When (and how) should we initialize the Sprite data member so that not having a default constructor won't cause us problems?

Once you've finished this step, you should be able to compile and link everything again—but you will still get warnings about unused variables because you haven't implemented everything needed in the Asciimation class yet.

Use the Member-Initialization List

To receive full idioms points, your constructor must properly use the member-initialization list. You can read about this expectation in Section 4.1 of the CS 70 Idioms Page, and you can read more about member-initialization lists in the lessons and in Chapter 1.1 of the Unofficial CS70 textbook.

Name Your Data Members Correctly

You should name your Sprite data member sprite_ to be consistent with other parts of the starter code.

Background: How Animation Works

Animation is a medium in which successive still images are rapidly presented one-after-another to give viewers the impression of smooth movements. To understand how this process works, imagine being presented with a still photograph of an object in motion. Then, a short while later, imagine you were shown another image of the same motion in progress (and then another, and another). As the delay between seeing the photographs decreases, the depicted motion would begin to appear smoother—it would be as if you were watching the original motion itself rather than a series of snapshots. The point at which a viewer perceives smooth motion from successively presented still images is known as the flicker-fusion threshold. It occurs for most humans when these images (known as frames) are presented at a rate of about 10–15 still images per second.

In traditional animation, frames might be drawn directly onto celluloid (“cel” animation), photographed physical objects (as in plasticine or clay animation), or “rendered” with computers (where each frame is computed from various data sources). But for this assignment we will be using the terminal to display our animation.

What's Already Done

We've given you an implementation for the play member function in the Asciimation class. It controls a loop to update and display a movie until the user exits by pressing q. You shouldn't need to modify this code at all, but you should read through it and make sure you understand how it works.

The content that is displayed by play is determined by a few other member functions of the Asciimation class:

• clearContents wipes out whatever was on the screen in the previous step by stepping through the character array and replacing everything with spaces.
• updateContents copies characters from the movie's sprite to its character array. It should first call clearContents. Then it should loop through all of the characters in the sprite using its getCharAt function, placing each character at the right spot in the movie's character array.
• copyToScreen copies characters from the movie's character array to the screen. It should use the ncurses function mvaddch to copy each element of the movie's character array to the right spot on the screen.

Your Task

Complete the implementation of these three functions to make the display system work:

1. clearContents: This private member function should loop through the entire character array and set each character to a space (' ').

2. updateContents: This function should:

3. First call clearContents to clear the display
4. Then loop through each row and column of the sprite
5. For each character, check if it would be visible on screen (considering the sprite's position)

6. If visible, copy the character from the sprite to the appropriate position in the movie's character array

7. copyToScreen: This function should:

8. Loop through each position in the movie's character array
9. Use mvaddch to place each character at the correct screen position

mvaddch(5, 10, 'X');  // Places an 'X' at row 5, column 10

index = row * width + column

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