问题
I am taking a computer graphics class that teaches us how to use OpenGL with the glut libraries. I have an idea for a final project that involves lighting and textures being put on a dinosaur model that I found online. My first step is to simplify the existing online code so I can begin working on my project.
Unfortunately, the online code for this model is broken, and I cannot seem to figure it out. I am not sure what gluTessCallback does, but my program is very upset with two lines of this code that is making it impossible to run this program on Visual Studio 2012.
Below is the code, and I have indicated which two lines are giving me the trouble.
typedef enum {
RESERVED, BODY_SIDE, BODY_EDGE, BODY_WHOLE, ARM_SIDE, ARM_EDGE, ARM_WHOLE,
LEG_SIDE, LEG_EDGE, LEG_WHOLE, EYE_SIDE, EYE_EDGE, EYE_WHOLE, DINOSAUR
} displayLists;
GLfloat angle = -150; /* in degrees */
GLboolean doubleBuffer = GL_TRUE, iconic = GL_FALSE, keepAspect = GL_FALSE;
int moving, begin;
int W = 300, H = 300;
GLdouble bodyWidth = 2.0;
int newModel = 1;
GLfloat body[][2] = { { 0, 3 },{ 1, 1 },{ 5, 1 },{ 8, 4 },{ 10, 4 },{ 11, 5 },
{ 11, 11.5 },{ 13, 12 },{ 13, 13 },{ 10, 13.5 },{ 13, 14 },{ 13, 15 },{ 11, 16 },
{ 8, 16 },{ 7, 15 },{ 7, 13 },{ 8, 12 },{ 7, 11 },{ 6, 6 },{ 4, 3 },{ 3, 2 },
{ 1, 2 } };
GLfloat arm[][2] = { { 8, 10 },{ 9, 9 },{ 10, 9 },{ 13, 8 },{ 14, 9 },{ 16, 9 },
{ 15, 9.5 },{ 16, 10 },{ 15, 10 },{ 15.5, 11 },{ 14.5, 10 },{ 14, 11 },{ 14, 10 },
{ 13, 9 },{ 11, 11 },{ 9, 11 } };
GLfloat leg[][2] = { { 8, 6 },{ 8, 4 },{ 9, 3 },{ 9, 2 },{ 8, 1 },{ 8, 0.5 },{ 9, 0 },
{ 12, 0 },{ 10, 1 },{ 10, 2 },{ 12, 4 },{ 11, 6 },{ 10, 7 },{ 9, 7 } };
GLfloat eye[][2] = { { 8.75, 15 },{ 9, 14.7 },{ 9.6, 14.7 },{ 10.1, 15 },
{ 9.6, 15.25 },{ 9, 15.25 } };
GLfloat lightZeroPosition[] = { 10.0, 4.0, 10.0, 1.0 };
GLfloat lightZeroColor[] = { 0.8, 1.0, 0.8, 1.0 }; /* green-tinted */
GLfloat lightOnePosition[] = { -1.0, -2.0, 1.0, 0.0 };
GLfloat lightOneColor[] = { 0.6, 0.3, 0.2, 1.0 }; /* red-tinted */
GLfloat skinColor[] = { 0.1, 1.0, 0.1, 1.0 }, eyeColor[] = { 1.0, 0.2, 0.2, 1.0 };
void
extrudeSolidFromPolygon(GLfloat data[][2], unsigned int dataSize,
GLdouble thickness, GLuint side, GLuint edge, GLuint whole)
{
static GLUtriangulatorObj *tobj = NULL;
GLdouble vertex[3], dx, dy, len;
int i;
int count = dataSize / (int)(2 * sizeof(GLfloat));
if (tobj == NULL) {
tobj = gluNewTess(); /* create and initialize a GLU
polygon tesselation object */
/////////////////////////////////////////////////////////////////////////////////////////
// THESE LINES WILL NOT COMPILE. Says that the glBegin and glVertex2fv are incompatable.
gluTessCallback(tobj, GLU_BEGIN, glBegin);
gluTessCallback(tobj, GLU_VERTEX, glVertex2fv); /* semi-tricky */
/////////////////////////////////////////////////////////////////////////////////////////
gluTessCallback(tobj, GLU_END, glEnd);
}
glNewList(side, GL_COMPILE);
glShadeModel(GL_SMOOTH); /* smooth minimizes seeing
tessellation */
gluBeginPolygon(tobj);
/////////////////////////////////////////////////////////////////////////////////////////
// ALSO A PROBLEM WITH THIS SECTION OF CODE?
for (i = 0; i < count; i++) {
vertex[0] = data[i][0];
vertex[1] = data[i][1];
vertex[2] = 0;
gluTessVertex(tobj, vertex, data[i]);
}
gluEndPolygon(tobj);
glEndList();
/////////////////////////////////////////////////////////////////////////////////////////
glNewList(edge, GL_COMPILE);
glShadeModel(GL_FLAT); /* flat shade keeps angular hands
from being "smoothed" */
glBegin(GL_QUAD_STRIP);
for (i = 0; i <= count; i++) {
/* mod function handles closing the edge */
glVertex3f(data[i % count][0], data[i % count][1], 0.0);
glVertex3f(data[i % count][0], data[i % count][1], thickness);
/* Calculate a unit normal by dividing by Euclidean
distance. We * could be lazy and use
glEnable(GL_NORMALIZE) so we could pass in * arbitrary
normals for a very slight performance hit. */
dx = data[(i + 1) % count][1] - data[i % count][1];
dy = data[i % count][0] - data[(i + 1) % count][0];
len = sqrt(dx * dx + dy * dy);
glNormal3f(dx / len, dy / len, 0.0);
}
glEnd();
glEndList();
glNewList(whole, GL_COMPILE);
glFrontFace(GL_CW);
glCallList(edge);
glNormal3f(0.0, 0.0, -1.0); /* constant normal for side */
glCallList(side);
glPushMatrix();
glTranslatef(0.0, 0.0, thickness);
glFrontFace(GL_CCW);
glNormal3f(0.0, 0.0, 1.0); /* opposite normal for other side */
glCallList(side);
glPopMatrix();
glEndList();
}
void
makeDinosaur(void)
{
GLfloat bodyWidth = 3.0;
extrudeSolidFromPolygon(body, sizeof(body), bodyWidth,
BODY_SIDE, BODY_EDGE, BODY_WHOLE);
extrudeSolidFromPolygon(arm, sizeof(arm), bodyWidth / 4,
ARM_SIDE, ARM_EDGE, ARM_WHOLE);
extrudeSolidFromPolygon(leg, sizeof(leg), bodyWidth / 2,
LEG_SIDE, LEG_EDGE, LEG_WHOLE);
extrudeSolidFromPolygon(eye, sizeof(eye), bodyWidth + 0.2,
EYE_SIDE, EYE_EDGE, EYE_WHOLE);
glNewList(DINOSAUR, GL_COMPILE);
glMaterialfv(GL_FRONT, GL_DIFFUSE, skinColor);
glCallList(BODY_WHOLE);
glPushMatrix();
glTranslatef(0.0, 0.0, bodyWidth);
glCallList(ARM_WHOLE);
glCallList(LEG_WHOLE);
glTranslatef(0.0, 0.0, -bodyWidth - bodyWidth / 4);
glCallList(ARM_WHOLE);
glTranslatef(0.0, 0.0, -bodyWidth / 4);
glCallList(LEG_WHOLE);
glTranslatef(0.0, 0.0, bodyWidth / 2 - 0.1);
glMaterialfv(GL_FRONT, GL_DIFFUSE, eyeColor);
glCallList(EYE_WHOLE);
glPopMatrix();
glEndList();
}
void
recalcModelView(void)
{
glPopMatrix();
glPushMatrix();
glRotatef(angle, 0.0, 1.0, 0.0);
glTranslatef(-8, -8, -bodyWidth / 2);
newModel = 0;
}
void
redraw(void)
{
if (newModel)
recalcModelView();
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glCallList(DINOSAUR);
glutSwapBuffers();
}
/* ARGSUSED2 */
void
mouse(int button, int state, int x, int y)
{
if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN) {
moving = 1;
begin = x;
}
if (button == GLUT_LEFT_BUTTON && state == GLUT_UP) {
moving = 0;
}
}
/* ARGSUSED1 */
void
motion(int x, int y)
{
if (moving) {
angle = angle + (x - begin);
begin = x;
newModel = 1;
glutPostRedisplay();
}
}
GLboolean lightZeroSwitch = GL_TRUE, lightOneSwitch = GL_TRUE;
void
controlLights(int value)
{
switch (value) {
case 1:
lightZeroSwitch = !lightZeroSwitch;
if (lightZeroSwitch) {
glEnable(GL_LIGHT0);
}
else {
glDisable(GL_LIGHT0);
}
break;
case 2:
lightOneSwitch = !lightOneSwitch;
if (lightOneSwitch) {
glEnable(GL_LIGHT1);
}
else {
glDisable(GL_LIGHT1);
}
break;
}
glutPostRedisplay();
}
int
main(int argc, char **argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
glutCreateWindow("glutdino");
glutDisplayFunc(redraw);
glutMouseFunc(mouse);
glutMotionFunc(motion);
glutCreateMenu(controlLights);
glutAddMenuEntry("Toggle right light", 1);
glutAddMenuEntry("Toggle left light", 2);
glutAttachMenu(GLUT_RIGHT_BUTTON);
makeDinosaur();
glEnable(GL_CULL_FACE);
glEnable(GL_DEPTH_TEST);
glEnable(GL_LIGHTING);
glMatrixMode(GL_PROJECTION);
gluPerspective( /* field of view in degree */ 40.0,
/* aspect ratio */ 1.0,
/* Z near */ 1.0, /* Z far */ 40.0);
glMatrixMode(GL_MODELVIEW);
gluLookAt(0.0, 0.0, 30.0, /* eye is at (0,0,30) */
0.0, 0.0, 0.0, /* center is at (0,0,0) */
0.0, 1.0, 0.); /* up is in postivie Y direction */
glPushMatrix(); /* dummy push so we can pop on model
recalc */
glLightModeli(GL_LIGHT_MODEL_LOCAL_VIEWER, 1);
glLightfv(GL_LIGHT0, GL_POSITION, lightZeroPosition);
glLightfv(GL_LIGHT0, GL_DIFFUSE, lightZeroColor);
glLightf(GL_LIGHT0, GL_CONSTANT_ATTENUATION, 0.1);
glLightf(GL_LIGHT0, GL_LINEAR_ATTENUATION, 0.05);
glLightfv(GL_LIGHT1, GL_POSITION, lightOnePosition);
glLightfv(GL_LIGHT1, GL_DIFFUSE, lightOneColor);
glEnable(GL_LIGHT0);
glEnable(GL_LIGHT1);
glutMainLoop();
return 0; /* ANSI C requires main to return int. */
}
I tried to make it clear where the problem is. OpenGl is bringing me to my wit's end. Is there nowhere I can get a simple 3D dinosaur model to play with on the internet?
I hope you can provide me some insight on this gluTessCallback issue so I can get this working. All I want is a solid dinosaur model.
回答1:
Looking at the man page, the signature of the callback passed to gluTessCallback() depends on the enum value passed as the second argument. This means that if you're using C++, or a version of C that uses function prototypes, you will need a typecast to cast your function to the type expected by gluTessCallback().
According to the man page, the argument type is defined as _GLUfuncptr. However, that type is not defined in the glu.h header I found. The type according to the spec and header is a function with no arguments and a return type of GLvoid. You can define your own function type for this, and then cast to it:
typedef GLvoid (*TessFuncPtr)();
gluTessCallback(tobj, GLU_BEGIN, (TessFuncPtr)glBegin);
gluTessCallback(tobj, GLU_VERTEX, (TessFuncPtr)glVertex2fv);
If you're just learning OpenGL, you should be aware that almost all of the calls in this code are deprecated and obsolete. This includes:
- Immediate mode rendering (
glBegin,glEnd, etc). - Display lists.
- Matrix stack.
- Fixed function lighting and material definitions.
I think you would be much better off learning a current version of OpenGL. For example the tessellation functionality you are trying to use was defined close to 25 years ago. Aside from being deprecated, I don't think it was ever widely used in the first place.
来源：https://stackoverflow.com/questions/33600619/opengl-dinosaur-model-bug-glutesscallback-issue