TRIM.C

/* 
 * (c) Copyright 1993, Silicon Graphics, Inc. 
 *               1993-1995 Microsoft Corporation 
 * 
 * ALL RIGHTS RESERVED 
 * 
 * Please refer to OpenGL/readme.txt for additional information 
 * 
 */ 
 
/* 
 *  trim.c 
 *  This program draws a NURBS surface in the shape of a  
 *  symmetrical hill, using both a NURBS curve and pwl 
 *  (piecewise linear) curve to trim part of the surface. 
 */ 
#include "glos.h" 
 
#include <GL/gl.h> 
#include <GL/glu.h> 
#include <GL/glaux.h> 
 
void myinit(void); 
void init_surface(void); 
void CALLBACK display(void); 
void CALLBACK myReshape(GLsizei w, GLsizei h); 
 
GLfloat ctlpoints[4][4][3]; 
 
GLUnurbsObj *theNurb; 
 
/* 
 *  Initializes the control points of the surface to a small hill. 
 *  The control points range from -3 to +3 in x, y, and z 
 */ 
void init_surface(void) 
{ 
    int u, v; 
    for (u = 0; u < 4; u++) { 
    for (v = 0; v < 4; v++) { 
        ctlpoints[u][v][0] = 2.0*((GLfloat)u - 1.5); 
        ctlpoints[u][v][1] = 2.0*((GLfloat)v - 1.5); 
 
        if ( (u == 1 || u == 2) && (v == 1 || v == 2)) 
        ctlpoints[u][v][2] = 3.0; 
        else 
        ctlpoints[u][v][2] = -3.0; 
    } 
    }                
}                
             
/*  Initialize material property and depth buffer. 
 */ 
void myinit(void) 
{ 
    GLfloat mat_diffuse[] = { 0.6, 0.6, 0.6, 1.0 }; 
    GLfloat mat_specular[] = { 0.9, 0.9, 0.9, 1.0 }; 
    GLfloat mat_shininess[] = { 128.0 }; 
 
    glClearColor (0.0, 0.0, 0.0, 1.0); 
    glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse); 
    glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular); 
    glMaterialfv(GL_FRONT, GL_SHININESS, mat_shininess); 
 
    glEnable(GL_LIGHTING); 
    glEnable(GL_LIGHT0); 
    glDepthFunc(GL_LESS); 
    glEnable(GL_DEPTH_TEST); 
    glEnable(GL_AUTO_NORMAL); 
    glEnable(GL_NORMALIZE); 
 
    init_surface(); 
 
    theNurb = gluNewNurbsRenderer(); 
    gluNurbsProperty(theNurb, GLU_SAMPLING_TOLERANCE, 50.0); 
    gluNurbsProperty(theNurb, GLU_DISPLAY_MODE, GLU_FILL); 
} 
 
void CALLBACK display(void) 
{ 
    GLfloat knots[8] = {0.0, 0.0, 0.0, 0.0, 1.0, 1.0, 1.0, 1.0}; 
    GLfloat edgePt[5][2] = /* counter clockwise */ 
    {{0.0, 0.0}, {1.0, 0.0}, {1.0, 1.0}, {0.0, 1.0}, {0.0, 0.0}}; 
    GLfloat curvePt[4][2] = /* clockwise */  
    {{0.25, 0.5}, {0.25, 0.75}, {0.75, 0.75}, {0.75, 0.5}}; 
    GLfloat curveKnots[8] =  
    {0.0, 0.0, 0.0, 0.0, 1.0, 1.0, 1.0, 1.0}; 
    GLfloat pwlPt[4][2] = /* clockwise */  
    {{0.75, 0.5}, {0.5, 0.25}, {0.25, 0.5}}; 
 
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 
    glPushMatrix(); 
    glRotatef(330.0, 1.,0.,0.); 
    glScalef (0.5, 0.5, 0.5); 
 
    gluBeginSurface(theNurb); 
    gluNurbsSurface(theNurb,  
        8, knots, 
        8, knots, 
        4 * 3, 
        3, 
        &ctlpoints[0][0][0],  
        4, 4, 
        GL_MAP2_VERTEX_3); 
    gluBeginTrim (theNurb); 
    gluPwlCurve (theNurb, 5, &edgePt[0][0], 2, GLU_MAP1_TRIM_2); 
    gluEndTrim (theNurb); 
    gluBeginTrim (theNurb); 
    gluNurbsCurve (theNurb, 8, curveKnots, 2,  
        &curvePt[0][0], 4, GLU_MAP1_TRIM_2); 
    gluPwlCurve (theNurb, 3, &pwlPt[0][0], 2, GLU_MAP1_TRIM_2); 
    gluEndTrim (theNurb); 
    gluEndSurface(theNurb); 
         
    glPopMatrix(); 
    glFlush(); 
} 
 
void CALLBACK myReshape(GLsizei w, GLsizei h) 
{ 
    if (!h) return; 
    glViewport(0, 0, w, h); 
    glMatrixMode(GL_PROJECTION); 
    glLoadIdentity(); 
    gluPerspective (45.0, (GLdouble)w/(GLdouble)h, 3.0, 8.0); 
 
    glMatrixMode(GL_MODELVIEW); 
    glLoadIdentity(); 
    glTranslatef (0.0, 0.0, -5.0); 
} 
 
/*  Main Loop  
 */ 
int main(int argc, char** argv) 
{ 
    auxInitDisplayMode (AUX_SINGLE | AUX_RGB | AUX_DEPTH16); 
    auxInitPosition (0, 0, 500, 500); 
    auxInitWindow ("NURBS Surface"); 
    myinit(); 
    auxReshapeFunc (myReshape); 
    auxMainLoop(display); 
    return(0); 
}