Introduction to Game Programming. 9/14/17: Conditionals, Input

Transcription

1 Introduction to Game Programming 9/14/17: Conditionals, Input

2 Micro-review Games are massive collections of what-if questions that resolve to yes or no Did the player just click the mouse? Has our health run out? Are we within half a meter of the red door and holding the red key? These are boolean (bool) values true or false

3 Micro-review We frequently make the determination of whether something is true or false by making comparisons ==,!=, <, <=, >, >= We can chain comparisons together to ask more complex questions!, &&, Now that we have the condition, how do we ask the question with it?

4 Conditional Statements Control Flow Within Your Programs if if / else if / else if / else switch Make use of braces { }

5 Conditional Statements if Performs code within braces if the condition within parentheses is true if (true) { print( "This line will print." ); if (false) { print( "This line will NOT print." ); // The output of this code will be: // This line will print. All the code within the braces of the if statement executes

6 Conditional Statements Combining if statements with boolean operations bool night = true; bool fullmoon = false; if (night) { print( "It's night." ); if (!fullmoon) { print( "The moon is not full." ); if (night && fullmoon) { print( "Beware werewolves!!!" ); if (night &&!fullmoon) { print( "No werewolves tonight. (Whew!)" ); // The output of this code will be: // It's night. // The moon is not full. // No werewolves tonight. (Whew!)

7 Conditional Statements Combining if statements with comparison operators if (10 == 10 ) { print( "10 is equal to 10." ); if ( 10 > 20 ) { print( "10 is greater than 20." ); if ( 1.23f <= 3.14f ) { print( "1.23 is less than or equal to 3.14." ); if ( 1.23f >= 1.23f ) { print( "1.23 is greater than or equal to 1.23." ); if ( 3.14f!= Mathf.PI ) { print( "3.14 is not equal to + Mathf.PI + "." ); // + can be used to concatenate strings with other data types. // When this happens, the other data is converted to a string. } Beware of accidentally using = in an if statement!

8 Conditional Statements if / else Performs one action if true, and another if false bool night = false; if (night) { print( "It's night." ); } else { print( "What are you worried about?" ); // The output of this code will be: // What are you worried about?

9 Conditional Statements if / else if / else Possible to chain several else if clauses bool night = true; bool fullmoon = true; if (!night) { // Condition 1 (false) print( "It s daytime. What are you worried about?" ); } else if (fullmoon) { // Condition 2 (true) print( "Beware werewolves!!!" ); } else { // Condition 3 (not checked) print( "It's night, but the moon is not full." ); // The output of this code will be: // Beware werewolves!!!

10 Conditional Statements Nested if statements bool night = true; bool fullmoon = false; if (!night) { print( "It s daytime. Why are you worried about?" ); } else { if (fullmoon) { print( "Beware werewolves!!!" ); } else { print( "It's night, but the moon isn't full." ); // The output of this code will be: // It's night, but the moon isn't full.

11 Conditional Statements switch an alternative to several if statements Can only compare for equality Can only compare a single variable against literals int num = 3; switch (num) { // The variable in parentheses is being compared case (0): // Each case is a literal that is compared against num print( "The number is zero." ); break; // Each case must end with a break statement. case (1): print( "The number is one." ); break; case (2): print( "The number is two." ); break; default: // If none of the other cases are true, default will happen print( "The number is more than a couple." ); break; } // The switch statement ends with a closing brace. // The output of this code is: The number is more than a couple.

12 Conditional Statements switch can "fall through" to other cases int num = 3; switch (num) { case (0): print( "The number is zero." ); break; case (1): print( "The number is one." ); break; case (2): print( "The number is a couple." ); break; case (3): // case (3) falls through to case (4) case (4): // case (4) falls through to case (5) case (5): print( "The number is a few." ); break; default: print( "The number is more than a few." ); break; // The output of this code is: The number is a few.

13 Reading Input

14 Questions We Ask Is a key being pressed/held? Was a key just pressed or released? Where is the mouse cursor? Input.GetKey(key); Input.GetKeyDown(key); Input.GetKeyUp(key); Input.mousePosition; Vector3 \_( ツ )_/ Is a mouse button being pressed/held? Was a mouse button just clicked or released? Input.GetMouseButton(button); Input.GetMouseButtonDown(button); Input.GetMouseButtonUp(button);

15 What Do We Pass In For key or button? Do we want direct or indirect input? Direct: I want to know if the space bar was just pressed Input.GetKeyDown(KeyCode.Space); Indirect: I want to know if the key that s mapped to the jump command was just pressed Input.GetKeyDown( Jump );

16 How Do We Map Inputs to Commands? Input.GetAxis( Horizontal );

17 Kaboom!

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19 Data Tree sprite Apple sprite Basket sprite Score text High score text Sounds

20 Rules create three baskets at start when an apple collides with a basket, destroy the apple and increase the score when an apple falls off the bottom of the screen, delete all apples and remove the topmost basket if the deleted basket is the final basket, reset the level baskets follow the mouse create apples at a fixed time interval apples fall if the current score exceeds the high score, set the high score to match the current score tree constantly moves, occasionally changing direction

21 GameObjects and Components (Transforms are assumed) Apple Basket AppleTree Manager Sprite Renderer Collider2D Rigidbody2D custom script to track whether it s off screen Sprite Renderer Collider2D custom script to move to mouse cursor, destroy colliding apple, and set score Sprite Renderer custom script to move and to Instantiate apples Score custom script to destroy all apples and track baskets High Score Text Text

22 Homework #1(a) Tree drops apples once per second (InvokeRepeating()) Set basket(s) to horizontal mouse position (set transform.position to a new Vector3()).05% of frames, tree changes direction Random.value (returns float between 0f and 1f) Bring to class on Monday (not graded yet)