/***********************************************************************/ /* */ /* NAME : Terry Fleury PROGRAM : mp0 */ /* NET ID : cs318ta1 COURSE : CS318 - Fall 1999 */ /* DUE DATE : September 10, 1998 */ /* PURPOSE : The purpose of this program is to introduce the class */ /* to the basics of OpenGL. The program produces a */ /* spirograph using a certain number of line segments. */ /* The number of vertices can be an odd integer between */ /* 3 and 99 (inclusive). We also make the user input a */ /* "step size" to tell which vertices to connect. A */ /* "step size" of 1 makes successive vertices connected, */ /* while a step size of 2 would skip vertices, making */ /* more of a star pattern. The "step size" must be */ /* greater than 0 but less than the number of vertices. */ /* INPUT : Two command line parameters (integers) to specify the */ /* number of line segments/vertices and step size to draw */ /* the spirograph. For example, take the following input: */ /* mp0 5 2 */ /* This would draw a standard star with 5 vertices, */ /* connecting every other vertex with a line segment. */ /* Type 'q' to quit. */ /* */ /***********************************************************************/ #include #include #include #include /*************************/ /* FUNCTION PROTOTYPES */ /*************************/ void Initialize(void); void SetCameraPosition(void); void UpdateDisplay(void); void DrawSpirograph(void); void KeyPressed(unsigned char,int,int); void CheckParameters(int,char**); void ReshapeWindow(int,int); void QuitProgram(void); void PrintHelp(void); /**********************/ /* GLOBAL CONSTANTS */ /**********************/ const float TWOPI = 6.28318530718; /**********************/ /* GLOBAL VARIABLES */ /**********************/ int NumVertices; /* Number of circle vertices - command line parameter */ int StepSize; /* Which vertices to connect - command line parameter */ /***********************************************************************/ /* Initialize is called at program invocation and sets up the main */ /* window. */ /***********************************************************************/ void Initialize(void) { /* Initialize the window and color mode */ glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB); glutInitWindowSize(600,600); glutCreateWindow("CS318 MP0 - Solution"); glClearColor(0.0,0.0,0.0,0.0); /* Background is black */ SetCameraPosition(); } /***********************************************************************/ /* SetCameraPosition is called by several procedures to move the */ /* camera to the correct viewing position, and then sets GL_MODELVIEW */ /* to allow drawing of objects on the screen. For this MP, we view */ /* a 2D "circle" of radius 1 centered about the origin. */ /***********************************************************************/ void SetCameraPosition(void) { /* Set the viewing transformation */ glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluOrtho2D(-1.05,1.05,-1.05,1.05); glMatrixMode(GL_MODELVIEW); } /***********************************************************************/ /* UpdateDisplay is called by the main event loop to refresh the */ /* contents of the display and to show the spirograph. */ /***********************************************************************/ void UpdateDisplay(void) { glClear(GL_COLOR_BUFFER_BIT); /* Clear the main window */ DrawSpirograph(); /* Do the actual drawing of the spirograph */ glFlush(); /* Flush all output to the main window */ } /***********************************************************************/ /* DrawSpirograph is called by UpdateDisplay to draw the figure */ /* using the correct number of line segments and step size (stored in */ /* the global variables NumVertices and StepSize). The first vertex */ /* of the figure is located at (1,0), and subseqent vertices are */ /* located equidistant on a unit circle, proceeding counterclockwise. */ /***********************************************************************/ void DrawSpirograph(void) { int vert = 0; /* Counter for vertices around the figure */ float rad; /* Radians for position along unit circle */ glColor3f(1.0,1.0,1.0); /* Set the drawing color to white */ /* Loop around the circle (which is 2*PI around) plotting */ /* points at equidistant points along the unit circle. */ glBegin(GL_LINE_LOOP); while (vert != NumVertices) { rad = (float)vert * TWOPI / (float)NumVertices; glVertex2f(sin(rad),cos(rad)); vert += StepSize; if (vert > NumVertices) vert -= NumVertices; } glEnd(); } /***********************************************************************/ /* ReshapeWindow is called if the main window needs to be resized. */ /* Note that this function is not really needed for this MP, but is */ /* given here for subsequent MPs. */ /***********************************************************************/ void ReshapeWindow(int Width, int Height) { SetCameraPosition(); glViewport(0,0,Width,Height); } /***********************************************************************/ /* QuitProgram is called to exit gracefully. */ /***********************************************************************/ void QuitProgram(void) { exit(0); } /***********************************************************************/ /* KeyPressed is called whenever a key is pressed by the user. We */ /* check to see if the user hit 'q' or 'Q'. If so, we quit. */ /***********************************************************************/ void KeyPressed(unsigned char Key, int X, int Y) { if (toupper(Key) == 'Q') QuitProgram(); } /***********************************************************************/ /* CheckParameters reads in the number of line segments specified on */ /* the command line and stores it in the global variable NumVertices. */ /* The step size is stored in the global variable StepSize. Then, */ /* we check to see if NumVertices is an odd integer between 3 and 99 */ /* (inclusive), and StepSize is between 1 and (NumVertices-1) */ /* (inclusive). If any of these conditions fail, we print out a */ /* "usage" message and quit. */ /***********************************************************************/ void CheckParameters(int argc, char* argv[]) { if ((argc != 3) || ((NumVertices = atoi(argv[1])) < 3) || (NumVertices > 99) || ((NumVertices % 2) != 1) || ((StepSize = atoi(argv[2])) < 1) || (StepSize >= NumVertices)) { printf("Usage: mp0 \n"); printf(" - The number of vertices for spirograph.\n"); printf(" This number must be an odd integer between 3 and 99.\n"); printf(" - Tells which vertices to connect with lines.\n"); printf(" A 'stepsize' of 1 would connect consecutive points\n"); printf(" to generate a 'circle'.\n"); printf(" This number must be between 1 and (vertices-1).\n"); QuitProgram(); } } /***********************************************************************/ /* PrintHelp is called at program startup to print out a short help */ /* message on how to use the program. */ /***********************************************************************/ void PrintHelp(void) { printf("CS318 - MP0 - OpenGL Introduction\n"); printf("Type 'q' or 'Q' to Quit Program\n"); fflush(NULL); /* Make sure all output shows up */ } /**************************/ /* BEGIN MAIN PROGRAM */ /**************************/ int main(int argc, char* argv[]) { glutInit(&argc,argv); /* Check to see if the user specified the number of vertices and step size */ CheckParameters(argc,argv); PrintHelp(); Initialize(); /* Set up main window and variables */ /* Set the GLUT Callback Functions */ glutKeyboardFunc(KeyPressed); glutReshapeFunc(ReshapeWindow); glutDisplayFunc(UpdateDisplay); glutMainLoop(); return 0; /* Required by ANSI C */ } /**************************/ /* END MAIN PROGRAM */ /**************************/