Question

I have a quite strange issue. Please, look at these screenshots:

Code of that object:

void prostopadloscian(float x, float y, float z, float red, float green, float blue)
{
    glBegin(GL_QUADS);
        glColor3f(red, green, blue);

        glNormal3f(-x,-y,-z);
        glVertex3f(-x,-y,-z);
        glNormal3f(x,-y,-z);
        glVertex3f(x,-y,-z);
        glNormal3f(x,-y,z);
        glVertex3f(x,-y,z);
        glNormal3f(-x,-y,z);
        glVertex3f(-x,-y,z);

        glNormal3f(-x,y,-z);
        glVertex3f(-x,y,-z);
        glNormal3f(x,y,-z);
        glVertex3f(x,y,-z);
        glNormal3f(x,y,z);
        glVertex3f(x,y,z);
        glNormal3f(-x,y,z);
        glVertex3f(-x,y,z);

        glNormal3f(-x,y,z);
        glVertex3f(-x,y,z);
        glNormal3f(-x,-y,z);
        glVertex3f(-x,-y,z);
        glNormal3f(-x,-y,-z);
        glVertex3f(-x,-y,-z);
        glNormal3f(-x,y,-z);
        glVertex3f(-x,y,-z);

        glNormal3f(-x,-y,-z);
        glVertex3f(-x,-y,-z);
        glNormal3f(x,-y,-z);
        glVertex3f(x,-y,-z);
        glNormal3f(x,y,-z);
        glVertex3f(x,y,-z);
        glNormal3f(-x,y,-z);
        glVertex3f(-x,y,-z);

        glNormal3f(x,y,z);
        glVertex3f(x,y,z);
        glNormal3f(x,-y,z);
        glVertex3f(x,-y,z);
        glNormal3f(x,-y,-z);
        glVertex3f(x,-y,-z);
        glNormal3f(x,y,-z);
        glVertex3f(x,y,-z);

        glNormal3f(-x,y,z);
        glVertex3f(-x,y,z);
        glNormal3f(-x,-y,z);
        glVertex3f(-x,-y,z);
        glNormal3f(-x,-y,-z);
        glVertex3f(-x,-y,-z);
        glNormal3f(-x,y,-z);
        glVertex3f(-x,y,-z);
    glEnd();
}
    void bed()
    {
        glPushMatrix();
            glTranslatef(-1.6, 0, 4.6);
            prostopadloscian(0.2, 0.25, 0.2, 0.35, 0.16, 0.14);
        glPopMatrix();
        glPushMatrix();
            glTranslatef(1.6, 0, 4.6);
            prostopadloscian(0.2, 0.25, 0.2, 0.35, 0.16, 0.14);
        glPopMatrix();
        glPushMatrix();
            glTranslatef(-1.6, 0, -4.6);
            prostopadloscian(0.2, 0.25, 0.2, 0.35, 0.16, 0.14);
        glPopMatrix();
        glPushMatrix();
            glTranslatef(1.6, 0, -4.6);
            prostopadloscian(0.2, 0.25, 0.2, 0.35, 0.16, 0.14);
        glPopMatrix();

        glPushMatrix();
            glTranslatef(0.0, 0.55, 0.0);
            prostopadloscian(2,0.3,5,0.85,0.85,0.95);
        glPopMatrix();
    }

my display() function starts at

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glClearColor(1.0, 1.0, 1.0, 1.0); 

glEnable(GL_DEPTH_TEST);
glDisable(GL_TEXTURE_2D);
glLoadIdentity();

How to get rid of this ugly effect?

Answer 1

Yeah, those prostopadloscians do look a bit strange. It’s hard to say for sure from these shots, but some things to look at:

• Is backface culling enabled?
• If so, are you specifying the vertices in the right order?
• Are your front and back clipping plane not too far apart?
• Does your depth buffer have enough bits for the clipping plane distance you’re using?
• Are your normals all pointing the right way? (Hint: no. Unless you’re being tricky, each face should need only one glNormal call.)