OpenGL での描画結果が表示されない

前提・実現したいこと

OpenGL でNURBS 曲面を作成しております．
合計１６点の制御点での実装はできたのですが，それ以上制御点数を
増やすとエラーは出ないのですが，描画結果が表示されません．
どのような原因が考えられるでしょうか．

回答お待ちしております．

#include <GL/glut.h>
#include <stdlib.h>
#include <math.h>

GLfloat ctlpoints[6][6][3] = {
{{0,0,0},
{0,0.33,0},
{0,0.66,0},
{0,1,0}},
{{6,0,2},
{6,0.33,2},
{6,0.66,2},
{6,1,2}},
{{3,0,4},
{3,0.33,4},
{3,0.66,4},
{3,1,4}},
{{0,0,4},
{0,0.33,4},
{0,0.66,4},
{0,1,4}},
{{-3,2,2},
{-3,2.33,2},
{-3,2.66,2},
{-3,3,2}},
{{3,2,0},
{3,2.33,0},
{3,2.66,0},
{3,3,0}}
};
int showPoints = 0;
GLfloat knotu[8] = { 0,0,0,0,1,1,1,1 };
GLfloat knotv[8] = { 0,0,0,0,1,1,1,1 };

GLUnurbsObj* theNurb;

void init(void)
{
GLfloat mat_diffuse[] = { 0.7, 0.7, 0.7, 1.0 };
GLfloat mat_specular[] = { 1.0, 1.0, 1.0, 1.0 };
GLfloat mat_shininess[] = { 100.0 };

glClearColor(1.0, 1.0, 1.0, 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);  /* 法線の計算 */
glEnable(GL_NORMALIZE);    /* 正規化 */



theNurb = gluNewNurbsRenderer();  /* NURBS オブジェクトを作成 */
gluNurbsProperty(theNurb, GLU_SAMPLING_TOLERANCE, 100.0);
gluNurbsProperty(theNurb, GLU_DISPLAY_MODE, GLU_FILL);

}

double xAngle = 0.0, yAngle = 0.0;
void display(void)
{
int i, j;

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glPushMatrix();
glRotated(xAngle, 1, 0, 0);
glRotated(yAngle, 0, 1, 0);
glScalef(0.5, 0.5, 0.5);

gluBeginSurface(theNurb);
gluNurbsSurface(theNurb, 10, knotu, 10, knotv, 4 * 3, 3,
	&ctlpoints[0][0][0],  6,4, GL_MAP2_VERTEX_3);
gluEndSurface(theNurb);

if (showPoints) {
	glPointSize(5.0);
	glDisable(GL_LIGHTING);
	glColor3f(1.0, 0.0, 0.0);
	glBegin(GL_POINTS);
	for (i = 0; i < 6; i++)
		for (j = 0; j < 4; j++)
			glVertex3f(ctlpoints[i][j][0],
				ctlpoints[i][j][1],
				ctlpoints[i][j][2]);
	glEnd();
	glEnable(GL_LIGHTING);
}
glPopMatrix();
glFlush();

}

void resize(int w, int 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);

}

void keyboard(unsigned char key, int x, int y)
{
switch (key) {
case 'c':
case 'C':
showPoints = !showPoints;
glutPostRedisplay();
break;
case '\33':
case 'q':
case 'Q':
exit(0);
break;
default:
break;
}
}
int xStart, yStart;
bool mouseFlag = GL_FALSE;
void myMouseFunc(int button, int state, int x, int y)
{
if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN)
{
xStart = x;
yStart = y;
mouseFlag = GL_TRUE;
}
else
{
mouseFlag = GL_FALSE;

}

void myMouseMotion(int x, int y)
{
int xdis, ydis;
double a = 0.5;

if (mouseFlag == GL_FALSE)return;

xdis = x - xStart;
ydis = y - yStart;

xAngle += (double)ydis * a;
yAngle += (double)xdis * a;

xStart = x;
yStart = y;
glutPostRedisplay();

}

int main(int argc, char** argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutCreateWindow(argv[0]);
init();
glutReshapeFunc(resize);
glutDisplayFunc(display);
glutKeyboardFunc(keyboard);
glutMouseFunc(myMouseFunc);
glutMotionFunc(myMouseMotion);
glutMainLoop();

return 0;

}

行動規範の内容に同意します

回答1件

ベストアンサー

NURBS曲面は使ったことがなく、ちょこっと検索しただけの回答で申し訳ないですが、ノットの数が狂っているんじゃないでしょうか?
制御点が

C
1GLfloat ctlpoints[6][4][3] = {
2    {{ 0, 0, 0}, { 0, 0.33, 0}, { 0, 0.66, 0}, { 0, 1, 0}},
3    {{ 6, 0, 2}, { 6, 0.33, 2}, { 6, 0.66, 2}, { 6, 1, 2}},
4    {{ 3, 0, 4}, { 3, 0.33, 4}, { 3, 0.66, 4}, { 3, 1, 4}},
5    {{ 0, 0, 4}, { 0, 0.33, 4}, { 0, 0.66, 4}, { 0, 1, 4}},
6    {{-3, 2, 2}, {-3, 2.33, 2}, {-3, 2.66, 2}, {-3, 3, 2}},
7    {{ 3, 2, 0}, { 3, 2.33, 0}, { 3, 2.66, 0}, { 3, 3, 0}}
8};

のとき、U方向の階数が6なら...

C
1GLfloat knotu[12] = {
2    0, 0, 0, 0, 0, 0,
3    1, 1, 1, 1, 1, 1
4};

C
1    gluBeginSurface(theNurb);
2    gluNurbsSurface(theNurb, 12, knotu, 8, knotv, 4 * 3, 3,
3                    &ctlpoints[0][0][0], 6, 4, GL_MAP2_VERTEX_3);
4    gluEndSurface(theNurb);

U方向の階数が4なら...

C
1GLfloat knotu[10] = {
2    0, 0, 0, 0,
3    0.33,
4    0.66,
5    1, 1, 1, 1
6};

C
1    gluBeginSurface(theNurb);
2    gluNurbsSurface(theNurb, 10, knotu, 8, knotv, 4 * 3, 3,
3                    &ctlpoints[0][0][0], 4, 4, GL_MAP2_VERTEX_3);
4    gluEndSurface(theNurb);