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OpenGL - Why are my objects transparent?

I am trying to make a motorcycle with primitive forms. For some reason, the forms I made are cross-cutting. I do not indicate any alpha anywhere; here is my code:

#include <GL/glut.h> #include <math.h> GLUquadricObj *quadratic; static int isWire = 0; // Is wireframe? static int distance = 10; static float angleH = 0; static float angleV = 0; static float R = 2.0; // Radius of hemisphere. static int p = 4; // Number of longitudinal slices. static int q = 6; // Number of latitudinal slices. #define PI 3.14159265358979324 static unsigned int pipe, seat, cover, wheel, wheelCenter, cycles; // parts of the motorcycle to make as display lists. GLUquadricObj *cylinder; void drawCoordinates(); void drawMotorcycle(); void drawTrailer(); void drawHemisphere(); void drawCylinder(float x, float y, float z); void drawHandle(float x, float y, float z); void drawLight(); void drawBase(); void setup(); void display () { /* clear window */ glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); gluLookAt(distance*cos(angleH), distance*cos(angleV), distance*sin(angleH), 0.0, 0.0, 0.0, 0.0, 1.0, 0.0); /* future matrix manipulations should affect the modelview matrix */ glMatrixMode(GL_MODELVIEW); if (isWire) glPolygonMode(GL_FRONT_AND_BACK, GL_LINE); else glPolygonMode(GL_FRONT_AND_BACK, GL_FILL); glPushMatrix(); drawCoordinates(); glPushMatrix(); glTranslatef(0.0, 0.0, 0.0); // Move the motorcycle around the world space drawMotorcycle(); drawTrailer(); glPopMatrix(); glPopMatrix(); /* flush drawing routines to the window */ glFlush(); } void drawCoordinates() { /***************** DRAW AXIS *****************/ glPushMatrix(); GLUquadricObj *xAxis; xAxis=gluNewQuadric(); glColor3f(1,0,0); glRotatef(-90, 0, 1, 0); gluCylinder(xAxis,0.05,0.05,1,5,5); glPopMatrix(); glPushMatrix(); GLUquadricObj *yAxis; yAxis=gluNewQuadric(); glColor3f(0,1,0); glRotatef(-90, 1, 0, 0); gluCylinder(yAxis,0.05,0.05,1,5,5); glPopMatrix(); glPushMatrix(); GLUquadricObj *zAxis; zAxis=gluNewQuadric(); glColor3f(0,0,1); gluCylinder(zAxis,0.05,0.05,1,5,5); glPopMatrix(); /***************** END OF DRAW AXIS *****************/ } void drawMotorcycle() { //DRAW ENGINE glPushMatrix(); //drawCoordinates(); glColor3f(.6, 0, 0); glScalef(1.4, 0.8, 1.0); glutSolidSphere(1,8,8); glPushMatrix(); //drawCoordinates(); glPopMatrix(); glPopMatrix(); //DRAW PIPES UNDER ENGINE glPushMatrix(); glRotatef(-90, 1, 0, 0); glRotatef(80, 0, 1, 0); glTranslatef(0.5, 1.0, -1.5); glCallList(pipe); glTranslatef(0.0, -2.0, 0.0); glCallList(pipe); glPopMatrix(); //DRAW SEAT glPushMatrix(); glPushMatrix(); glRotatef(15, 0, 0, 1); glTranslatef(-2.0, -0.4, 0.0); glScalef(2.0, 0.2, 1.2); glCallList(seat); glPopMatrix(); //DRAW BACK SEAT glRotatef(-40, 0, 0, 1); glTranslatef(-2.3, -2.8, 0.0); glScalef(2.0, 0.2, 1.2); glCallList(seat); glPopMatrix(); //DRAW FRONT PLATE glPushMatrix(); glRotatef(120, 0, 0, 1); glTranslatef(0.8, -1.3, 0.0); glScalef(2.0, 0.2, 1.35); glColor3f(0.5,0.0,0.0); glutSolidCube(1); glPushMatrix(); //drawCoordinates(); glPopMatrix(); glPopMatrix(); //DRAW FRONT PIPES glPushMatrix(); glRotatef(-90, 1, 0, 0); glRotatef(-30, 0, 1, 0); glTranslatef(1.3, -0.9, -5.7); glScalef(1.0, 1.0, 2.5); glCallList(pipe); glTranslatef(0.0, 1.7, 0.0); glCallList(pipe); glPopMatrix(); //DRAW WHEEL COVERS glPushMatrix(); glTranslatef(3.5, -3.0, 0.0); glScalef(1.0, 0.5, 1.0); glRotatef(45, 0, 0, 1); glCallList(cover); glTranslatef(-5.5, 0.0, 0.0); glRotatef(-100, 0, 0, 1); glTranslatef(-8.5, 0.2, 0.0); glCallList(cover); glPopMatrix(); //DRAW WHEELS glPushMatrix(); glTranslatef(3.9, -4.1, 0.0); glCallList(wheel); glTranslatef(-9.2, 2.0, 0.0); glCallList(wheel); glPopMatrix(); //DRAW WHEEL CENTER PIECES glPushMatrix(); glTranslatef(3.9, -4.1, 0.0); glCallList(wheelCenter); glTranslatef(-9.2, 2.0, 0.0); glCallList(wheelCenter); glPopMatrix(); //DRAW CYCLES AROUND WHEELS glPushMatrix(); glTranslatef(3.9, -4.1, 0.0); glRotatef(-90, 1, 0, 0); for(int i=0; i<8; i++) { glRotatef(45, 0, 1, 0); glPushMatrix(); glCallList(cycles); glPopMatrix(); } glTranslatef(-9.2, 0.0, 2.0); for(int i=0; i<8; i++) { glRotatef(45, 0, 1, 0); glPushMatrix(); glCallList(cycles); glPopMatrix(); } glPopMatrix(); //DRAW HANDLE BARS glPushMatrix(); glTranslatef(0.2, 2.0, 0.0); glRotatef(-45, 1, 0, 0); glScalef(0.7, 0.7, 0.7); glCallList(pipe); glRotatef(-90, 1, 0, 0); glCallList(pipe); glPopMatrix(); //DRAW LIGHT glPushMatrix(); glTranslatef(1.0, 1.0, 0.0); glColor3f(0.5, 0.5, 0.0); //glScalef(1.0, 0.5, 1.0); glutSolidSphere(0.5, 5, 5); glPushMatrix(); //drawCoordinates(); glPopMatrix(); glPopMatrix(); //DRAW BASE glPushMatrix(); glRotatef(10.0, 0.0, 0.0, 1.0); glScalef(3.5, 1.5, 1.0); glTranslatef(-0.4, -1.0, 0.0); glColor3f(0.3, 0.3, 0.3); glutSolidCube(1); glPopMatrix(); //GAS TANK glPushMatrix(); glScalef(2.5, 1.0, 0.8); glTranslatef(-0.8, -1.7, -1.4); glCallList(pipe); glPopMatrix(); } void drawTrailer() { //DRAW BODY glPushMatrix(); glColor3f(0.0, 0.0, 0.3); glScalef(2.0, 2.5, 1.5); glTranslatef(-4.5, -0.5, 0.0); glutSolidCube(1); glPopMatrix(); //DRAW WHEELS glPushMatrix(); glPushMatrix(); glScalef(0.8, 0.8, 0.8); glTranslatef(-12.0, -1.5, 2.0); glCallList(wheel); glCallList(wheelCenter); glRotatef(90, 1, 0, 0); for(int i=0; i<8; i++) { glRotatef(45, 0, 1, 0); glPushMatrix(); glCallList(cycles); glPopMatrix(); } glPopMatrix(); glPushMatrix(); glScalef(0.8, 0.8, 0.8); glTranslatef(-12.0, -1.5, -2.0); glCallList(wheel); glCallList(wheelCenter); glRotatef(90, 1, 0, 0); for(int i=0; i<8; i++) { glRotatef(45, 0, 1, 0); glPushMatrix(); glCallList(cycles); glPopMatrix(); } glPopMatrix(); glPopMatrix(); //DRAW CONNECTION TO MOTORCYCLE glPushMatrix(); glRotatef(90, 0, 1, 0); glTranslatef(0.0, -1.0, -8.0); glCallList(pipe); glPopMatrix(); } void drawHemisphere() { for(int j = 0; j < q; j++) { // One latitudinal triangle strip. glBegin(GL_TRIANGLE_STRIP); for(int i = 0; i <= p; i++) { glVertex3f( R * cos( (float)(j+1)/q * PI/2.0 ) * cos( 2.0 * (float)i/p * PI ), R * sin( (float)(j+1)/q * PI/2.0 ), R * cos( (float)(j+1)/q * PI/2.0 ) * sin( 2.0 * (float)i/p * PI ) ); glVertex3f( R * cos( (float)j/q * PI/2.0 ) * cos( 2.0 * (float)i/p * PI ), R * sin( (float)j/q * PI/2.0 ), R * cos( (float)j/q * PI/2.0 ) * sin( 2.0 * (float)i/p * PI ) ); } glEnd(); } } void reshape (int w, int h) { // (Window of width = zero is not possible). if(h == 0) h = 1; float ratio = 1.0* w / h; // Reset the coordinate system before modifying glMatrixMode(GL_PROJECTION); glLoadIdentity(); // Set the viewport to be the entire window glViewport(0, 0, w, h); // Set the correct perspective. gluPerspective(90,ratio,-1,1); } // Keyboard input processing routine. void keyInput(unsigned char key, int x, int y) { switch(key) { case 'c' : distance = 10; angleH=0; angleV=0.0; break; case 'C' : distance = 10; angleH=0; angleV=0.0; break; case 'f': distance = (distance == 4)? 4:distance-1; break; case 'F': distance = (distance == 4)? 4:distance-1; break; case 'b': distance = (distance == 20)? 20:distance+1; break; case 'B': distance = (distance == 20)? 20:distance+1; break; case 'w': if (isWire == 0) isWire = 1; else isWire = 0; break; case 'W': if (isWire == 0) isWire = 1; else isWire = 0; break; //case 27: exit(0); break; default: break; } } void specialKeyboard(int key, int x, int y) { switch (key) { case GLUT_KEY_RIGHT: angleH -= .2; break; case GLUT_KEY_LEFT: angleH += .2; break; case GLUT_KEY_UP: angleV += .2; break; case GLUT_KEY_DOWN: angleV -= .2; break; } } void update(void){ glutPostRedisplay(); } void setup() { // PARTS pipe = glGenLists(1); seat = glGenLists(1); cover = glGenLists(1); wheel = glGenLists(1); wheelCenter = glGenLists(1); cycles = glGenLists(1); glNewList(pipe, GL_COMPILE); // Any cylinder on the motorcycle GLUquadricObj *cylinder; cylinder=gluNewQuadric(); glPushMatrix(); glColor3f(.5,.5,.5); gluCylinder(cylinder,0.2,0.2,3,5,5); glPushMatrix(); //drawCoordinates(); glPopMatrix(); glPopMatrix(); glEndList(); glNewList(seat, GL_COMPILE); glPushMatrix(); glColor3f(0.5, 0.35, 0.05); glutSolidCube(1); glPushMatrix(); //drawCoordinates(); glPopMatrix(); glPopMatrix(); glEndList(); glNewList(cover, GL_COMPILE); glPushMatrix(); glColor3f(0.5, 0.0, 0.0); drawHemisphere(); glPushMatrix(); //drawCoordinates(); glPopMatrix(); glPopMatrix(); glEndList(); glNewList(wheel, GL_COMPILE); glPushMatrix(); glColor3f(0.1, 0.1, 0.1); glutSolidTorus(0.2, 1.2, 20, 20); glPushMatrix(); //drawCoordinates(); glPopMatrix(); glPopMatrix(); glEndList(); glNewList(wheelCenter, GL_COMPILE); glPushMatrix(); glColor3f(0.4, 0.5, 0.5); glScalef(1.0, 0.5, 1.0); glutSolidSphere(0.8, 5, 5); glPushMatrix(); //drawCoordinates(); glPopMatrix(); glPopMatrix(); glEndList(); glNewList(cycles, GL_COMPILE); glColor3f(0.5, 0.5, 0.5); glScalef(0.25, 0.25, 0.25); cylinder=gluNewQuadric(); gluCylinder(cylinder,0.5,0.5,5,15,5); glEndList(); } int main (int argc, char** argv) { /* initialize GLUT, using any commandline parameters passed to the program */ glutInit(&argc,argv); /* setup the size, position, and display mode for new windows */ glutInitWindowSize(500,500); glutInitWindowPosition(0,0); glutInitDisplayMode( GLUT_RGB | GLUT_DEPTH ); /* create and set up a window */ glutCreateWindow("Motorcycle"); setup(); // Build all the display lists, ready to use glutIdleFunc(update); glutDisplayFunc(display); glutReshapeFunc(reshape); glutKeyboardFunc(keyInput); glutSpecialFunc(specialKeyboard); /* set up depth-buffering */ glEnable(GL_DEPTH_TEST); /* background color */ glClearColor(0.0f, 0.0f, 0.0f, 1.0f); /* tell GLUT to wait for events */ glutMainLoop(); return 0; }

You can rotate the camera using the arrow keys to see that objects are being viewed. How can i fix this? Is there anything else I can do to improve the code?

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2 answers

In reshape() :

 // Set the correct perspective. gluPerspective(90,ratio,-1,1);

I assume that you transliterated the parameters from the glOrtho() call, where negative zNear is perfectly legal.

From gluPerspective() docs :

zNear: indicates the distance from the viewer to the clipping plane (always positive) .

Try the following:

 gluPerspective(90,ratio,1,100);
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You need to add glEnable (GL_DEPTH_TEST); to your initialization function.

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Source: https://habr.com/ru/post/1440086/

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