This document describes GLUTetris, an OpenGL implementation of the classic Tetris game. It summarizes the key aspects of Tetris, including the goal of manipulating tetrominoes to clear horizontal lines without gaps. It also describes the OpenGL implementation, including use of lighting, textures, hierarchy and animation to replicate aspects of the original game. OpenAL is used to play background music and sound effects during game play.

1. GLUTetris
An OpenGL clone of the popular game Tetris
Prof. Marco Schaerf
Dipartimento di Informatica e Sistemistica
Giovanni Murru
Master in AI and Robotics
Computer Graphics Course

2. The Tetris Game
 Created in 1984 by Alexey Pajitnov, a computer engineer, with the help
of Dmitry Pavlovsky and Vadim Gerasimov
 Goal of the game is to manipulate the tetrominoes moving sideways or
rotating them by 90 degrees, with the intention of creating one up to
four horizontal lines of blocks without gaps.
 When such lines are created they disappear.
 When four lines are contemporary created, a Tetris score is done.
 The tetrominoes became part of the wall when they fall in the wall or in
the down edge of the game board.
 When the wall reaches the top of the game field, the game is over.

3. The Tetromino
 Tetromino is composed by 4 blocks in different
configurations.
 They are identified with letters.
 Left to right: I,J,L,O,S,T,Z

4. Binary Identification
 Tetrominoes are identified with binary matrices.
 28 4-by-4 binary matrices
 7 types of tetrominoes * 4 possible orientations
 Element of the matrix is:
 1 if occupied by one block,
 0 otherwise
 E.g.

5. The Collision Problem (1/2)
 The wall is a binary matrix of 20-by-10 elements with
the same notation used to represent tetrominoes
 A collision between the tetromino and the wall is
detected using an algorithm that checks the presence of
conflict in the same cell.
 i.e. a 1 value is present in the wall matrix at the relative
positions of the element occupied by a 1 in the tetromino
matrix.
 First-Act-Then-Confirm-Or-Refuse approach
 Virtual Movement -> Check -> Restore or Commit

6. The Collision Problem (2/2)
 An algorithm that checks if the tetromino is going
outside the game board limits or if it is in contact with
the wall with respect to the down movement.
 Two different behaviors when the Tetromino hits the
wall:
 CASE 1: Tetromino hits the wall during down movement, then
act making the tetromino part of the wall.
 CASE 2: Tetromino hits the wall during the left, right, or
rotation movement, then act denying the movement.

7. Level, Scores, and Lines
 The level number and the game speed are concurrently
increased each 10 cleared lines.
 The score has been assigned according to the Nintendo
scoring system, which gives a reward proportional to:
 Actual level
 Number of Lines contemporary deleted
Level Points for
1 Line
Points for
2 Lines
Points for
3 Lines
Points for
Tetris
N 40*N 100*N 300*N 1200*N

8. OpenGL Layer
 GLUT toolkit has been used.
 3d environment, although tetrominoes are constrained to
move in a vertical plane.
 Light
 Textures
 Anti-aliasing
 Blending
 Hierarchical objects

9. The Lights
 Light as a sum of different contributes:
 Ambient
 Diffuse and Specular Reflection
 Emission
 3 lights:
 LIGHT0: soft ambient light
 LIGHT1: left spotlight
 LIGHT2: right spotlight
 All the lights have a white neutral color.
 Blending and Anti-Aliasing are activated

10. Textures
 The textures are mapped in the tetrominoes and a spherical
sky.
 Tetrominoes are composed by four cubes, and the same
texture is applied to each side of the cube.
 Textures in the cube are applied so that the resulting output
is a mix between the original color of the cube and the
texture.
 GL_LINEAR used for both minification and magnification,
MIPMAP is disabled
 The sky is a flipped image applied to the surface of a sphere.

11. Hierarchy (1/3)
 The hierarchy is used in the animation that occurs when the
player makes a Tetris score, namely when he simultaneously
deletes 4 lines.
 Animation that makes the game board, including tetrominoes
and wall rotate of 180 degrees wrt the up axis, while the next
tetromino is rotating wrt the horizontal axis and the current
tetromino is translating with the rest of the wall but faster,
outside the field of view.
 The animation consist in a gameboard rotating while
tetrominoes and wall are fading because of the translation
movement.

12. Hierarchy (2/3)
Application
Game
Game Field
Wall
Current
Tetromino
Next
Tetromino
Sky

13. Hierarchy (3/3)
glPushMatrix();
//rotates the entire scene
glRotatef(angle_of_scene_rot, 0, 1, 0);
//draws the game field
this->dobj->drawCampo();
glPushMatrix();
//translates the wall an the tetrominoes to obtain a fade effect
glTranslatef(0, 0, effetto_scomparsa);
//draws the wall
this->dobj->drawWall(this->w);
glPushMatrix();
//translate the current tetromino so that it fades faster
glTranslatef(effetto_scomparsa_tetromino,0,0);
if(!this->game_over)
this->dobj->drawTetromino(this->t);
glPopMatrix();
glPushMatrix();
//rotates the next tetromino
glRotatef(effetto_rot_next_tetro, 1, 0, 0);
this->dobj->drawNextTetromino(this->next_t);
glPopMatrix();
glPopMatrix();
glPopMatrix();

14. Sounds
 Use of OpenAL library, a 3D cross platform audio API.
 Three themes songs:
 Original Nintendo Themes
 Sound when Game is Over
 Sound goes in pause when the game is put in pause.
 Sound is stopped when M is pressed

15. The End…