移植 NURBS 图面

  • 项目

下表列出了用于绘制 NURBS 图面及其等效 OpenGL 函数的 IRIS GL 函数。

IRIS GL 函数 OpenGL 函数 含义
bgnsurface gluBeginSurface 开始图面定义。
nurbssurface gluNurbsSurface 指定图面属性。
endsurface gluEndSurface 结束图面定义。

 

下表列出了 Surface 类型的 IRIS GL 参数及其等效的 OpenGL 参数。

IRIS GL 类型 OpenGL 类型 含义
N_V3D GL_MAP2_VERTEX_3 多项式曲线。
N_V3DR GL_MAP2_VERTEX_4 合理曲线。
N_C4D GL_MAP2_COLOR_4 控制点在 (R、G、B、A) 窗体中定义颜色图面。
N_C4DR
N_T2D GL_MAP2_TEXTURE_COORD_2 控制点是纹理坐标。
N_T2DR GL_MAP2_TEXTURE_COORD_3 控制点是纹理坐标。
GL_MAP2_NORMAL 控制点是正常值。

 

有关可用计算器类型的详细信息，请参阅 glMap2。

下面的代码示例绘制剪裁的 NURBS 图面：

/* 
 *  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 <GL/gl.h> 
#include <GL/glu.h> 
#include "aux.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_LEQUAL); 
    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 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 myReshape(GLsizei w, GLsizei h) 
{ 
    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_RGBA | AUX_DEPTH); 
    auxInitPosition (0, 0, 500, 500); 
    auxInitWindow (argv[0]); 
    myinit(); 
    auxReshapeFunc (myReshape); 
    auxMainLoop(display); 
}