florida.c

来自「OpeNGL超级宝典源代码. OpeNGL超级宝典源代码.」· C语言 代码 · 共 262 行

// Florida.c
// OpenGL SuperBible
// Demonstrates polygon tesselation
// Program by Richard S. Wright Jr.
#include "../../Common/OpenGLSB.h"	// System and OpenGL Stuff
#include "../../Common/GLTools.h"   // OpenGL Tools library
#include <math.h>

// Nuke CALLBACK for everybody but Windows
#ifndef WIN32
#define CALLBACK
#endif


/////////////////////////////////
// Coast Line Data
#define COAST_POINTS 24
GLdouble vCoast[COAST_POINTS][3] = {{-70.0, 30.0, 0.0 },
                                    {-50.0, 30.0, 0.0 },
                                    {-50.0, 27.0, 0.0 },
                                    { -5.0, 27.0, 0.0 },
                                    {  0.0, 20.0, 0.0 },
                                    {  8.0, 10.0, 0.0 },
                                    { 12.0,  5.0, 0.0 },
                                    { 10.0,  0.0, 0.0 },
                                    { 15.0,-10.0, 0.0 },
                                    { 20.0,-20.0, 0.0 },
                                    { 20.0,-35.0, 0.0 },
                                    { 10.0,-40.0, 0.0 },
                                    {  0.0,-30.0, 0.0 },
                                    { -5.0,-20.0, 0.0 },
                                    {-12.0,-10.0, 0.0 },
                                    {-13.0, -5.0, 0.0 },
                                    {-12.0,  5.0, 0.0 },
                                    {-20.0, 10.0, 0.0 },
                                    {-30.0, 20.0, 0.0 },
                                    {-40.0, 15.0, 0.0 },
                                    {-50.0, 15.0, 0.0 },
                                    {-55.0, 20.0, 0.0 },
                                    {-60.0, 25.0, 0.0 },
                                    {-70.0, 25.0, 0.0 }};

// Lake Okeechobee
#define LAKE_POINTS 4
GLdouble vLake[LAKE_POINTS][3] = {{ 10.0, -20.0, 0.0 },
                                  { 15.0, -25.0, 0.0 },
                                  { 10.0, -30.0, 0.0 },
                                  {  5.0, -25.0, 0.0 }};


// Which Drawing Method
#define DRAW_LOOPS      0
#define DRAW_CONCAVE    1
#define DRAW_COMPLEX    2
int iMethod = DRAW_LOOPS;   // Default, draw line loops

////////////////////////////////////////////////////////////////////
// Reset flags as appropriate in response to menu selections
void ProcessMenu(int value)
    {
    // Save menu identifier as method flag
    iMethod = value;
        
    // Trigger a redraw
    glutPostRedisplay();
    }
    
////////////////////////////////////////////////////////////////////
// Tesselation error callback
void CALLBACK tessError(GLenum error)
    {
    // Get error message string
    const char *szError = gluErrorString(error);
    
    // Set error message as window caption
    glutSetWindowTitle(szError);
    }
    
///////////////////////////////////////////////////
// Called to draw scene
void RenderScene(void)
    {
    int i;                  // Loop variable
      
    // Clear the window
    glClear(GL_COLOR_BUFFER_BIT);
         
    switch(iMethod)
        {
        case DRAW_LOOPS:                    // Draw line loops
            {
            glColor3f(0.0f, 0.0f, 0.0f);    // Just black outline
            
            // Line loop with coastline shape
            glBegin(GL_LINE_LOOP);
            for(i = 0; i < COAST_POINTS; i++)
                glVertex3dv(vCoast[i]);
            glEnd();

            // Line loop with shape of interior lake
            glBegin(GL_LINE_LOOP);
            for(i = 0; i < LAKE_POINTS; i++)
                glVertex3dv(vLake[i]);
            glEnd();
            }
            break;
            
        case DRAW_CONCAVE:              // Tesselate concave polygon
            {
            // Tesselator object
            GLUtesselator *pTess;
            
            // Green polygon
            glColor3f(0.0f, 1.0f, 0.0f); 
            
            // Create the tesselator object
            pTess = gluNewTess();
            
            // Set callback functions
            // Just call glBegin at begining of triangle batch
            gluTessCallback(pTess, GLU_TESS_BEGIN, glBegin);
            
            // Just call glEnd at end of triangle batch
            gluTessCallback(pTess, GLU_TESS_END, glEnd);
            
            // Just call glVertex3dv for each  vertex
            gluTessCallback(pTess, GLU_TESS_VERTEX, glVertex3dv);
            
            // Register error callback
            gluTessCallback(pTess, GLU_TESS_ERROR, tessError);
            
            // Begin the polygon
            gluTessBeginPolygon(pTess, NULL);
            
            // Gegin the one and only contour
            gluTessBeginContour(pTess);

            // Feed in the list of vertices
            for(i = 0; i < COAST_POINTS; i++)
                gluTessVertex(pTess, vCoast[i], vCoast[i]); // Can't be NULL
                
            // Close contour and polygon
            gluTessEndContour(pTess);
            gluTessEndPolygon(pTess);
            
            // All done with tesselator object
            gluDeleteTess(pTess);
            }
        break;
    
        case DRAW_COMPLEX:          // Tesselate, but with hole cut out
            {
            // Tesselator object
            GLUtesselator *pTess;
            
            // Green polygon
            glColor3f(0.0f, 1.0f, 0.0f); 

             // Create the tesselator object
            pTess = gluNewTess();
            
            // Set callback functions
            // Just call glBegin at begining of triangle batch
            gluTessCallback(pTess, GLU_TESS_BEGIN, glBegin);
            
            // Just call glEnd at end of triangle batch
            gluTessCallback(pTess, GLU_TESS_END, glEnd);
            
            // Just call glVertex3dv for each  vertex
            gluTessCallback(pTess, GLU_TESS_VERTEX, glVertex3dv);
            
            // Register error callback
            gluTessCallback(pTess, GLU_TESS_ERROR, tessError);

            // How to count filled and open areas
            gluTessProperty(pTess, GLU_TESS_WINDING_RULE, GLU_TESS_WINDING_ODD);
            
            // Begin the polygon
            gluTessBeginPolygon(pTess, NULL); // No user data
            
            // First contour, outline of state
            gluTessBeginContour(pTess);
            for(i = 0; i < COAST_POINTS; i++)
                gluTessVertex(pTess, vCoast[i], vCoast[i]);
            gluTessEndContour(pTess);
            
            // Second contour, outline of lake
            gluTessBeginContour(pTess);
            for(i = 0; i < LAKE_POINTS; i++)
                gluTessVertex(pTess, vLake[i], vLake[i]);
            gluTessEndContour(pTess);
            
            // All done with polygon
            gluTessEndPolygon(pTess);
            
            // No longer need tessellator object
            gluDeleteTess(pTess);            
            }
        break;
        }
        
    // Swap buffers
    glutSwapBuffers();
    }


// This function does any needed initialization on the rendering
// context. Basically, just make a blue background
void SetupRC()
    {
    // Blue background
    glClearColor(0.0f, 0.0f, 1.0f, 1.0f );
    }


////////////////////////////////////////////////////////////////
// Reset projection
void ChangeSize(int w, int h)
    {
    // Prevent a divide by zero
    if(h == 0)
        h = 1;

    // Set Viewport to window dimensions
    glViewport(0, 0, w, h);

    // Reset projection matrix stack
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();

    // Establish clipping volume (left, right, bottom, top, near, far)
    gluOrtho2D(-80, 35, -50, 50);


    // Reset Model view matrix stack
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    }

//////////////////////////////////////////////////////////////////
int main(int argc, char* argv[])
	{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
	glutInitWindowSize(500, 400);
	glutCreateWindow("Tesselated Florida");
	
	// Create the Menu
	glutCreateMenu(ProcessMenu);
	glutAddMenuEntry("Line Loops",DRAW_LOOPS);
	glutAddMenuEntry("Concave Polygon",DRAW_CONCAVE);
    glutAddMenuEntry("Complex Polygon",DRAW_COMPLEX);
	glutAttachMenu(GLUT_RIGHT_BUTTON);
	
	glutReshapeFunc(ChangeSize);
	glutDisplayFunc(RenderScene);
	SetupRC();
	glutMainLoop();

	return 0;
	}