Hi!
When i want to draw a cube why is this code correct
glBegin(GL_QUADS);
// top
glColor3f(1.0f, 0.0f, 0.0f);
glNormal3f(0.0f, 1.0f, 0.0f);
glVertex3f(-0.5f, 0.5f, 0.5f);
glVertex3f(0.5f, 0.5f, 0.5f);
glVertex3f(0.5f, 0.5f, -0.5f);
glVertex3f(-0.5f, 0.5f, -0.5f);
glEnd();
glBegin(GL_QUADS);
// front
glColor3f(0.0f, 1.0f, 0.0f);
glNormal3f(0.0f, 0.0f, 1.0f);
glVertex3f(0.5f, -0.5f, 0.5f);
glVertex3f(0.5f, 0.5f, 0.5f);
glVertex3f(-0.5f, 0.5f, 0.5f);
glVertex3f(-0.5f, -0.5f, 0.5f);
glEnd();
glBegin(GL_QUADS);
// right
glColor3f(0.0f, 0.0f, 1.0f);
glNormal3f(1.0f, 0.0f, 0.0f);
glVertex3f(0.5f, 0.5f, -0.5f);
glVertex3f(0.5f, 0.5f, 0.5f);
glVertex3f(0.5f, -0.5f, 0.5f);
glVertex3f(0.5f, -0.5f, -0.5f);
glEnd();
glBegin(GL_QUADS);
// left
glColor3f(0.0f, 0.0f, 0.5f);
glNormal3f(-1.0f, 0.0f, 0.0f);
glVertex3f(-0.5f, -0.5f, 0.5f);
glVertex3f(-0.5f, 0.5f, 0.5f);
glVertex3f(-0.5f, 0.5f, -0.5f);
glVertex3f(-0.5f, -0.5f, -0.5f);
glEnd();
glBegin(GL_QUADS);
// bottom
glColor3f(0.5f, 0.0f, 0.0f);
glNormal3f(0.0f, -1.0f, 0.0f);
glVertex3f(0.5f, -0.5f, 0.5f);
glVertex3f(-0.5f, -0.5f, 0.5f);
glVertex3f(-0.5f, -0.5f, -0.5f);
glVertex3f(0.5f, -0.5f, -0.5f);
glEnd();
glBegin(GL_QUADS);
// back
glColor3f(0.0f, 0.5f, 0.0f);
glNormal3f(0.0f, 0.0f, -1.0f);
glVertex3f(0.5f, 0.5f, -0.5f);
glVertex3f(0.5f, -0.5f, -0.5f);
glVertex3f(-0.5f, -0.5f, -0.5f);
glVertex3f(-0.5f, 0.5f, -0.5f);
glEnd();
and this for e.g. not
glBegin(GL_QUADS);
// top
glColor3f(1.0f, 0.0f, 0.0f);
glNormal3f(0.0f, 1.0f, 0.0f);
glVertex3f(-0.5f, 0.5f, 0.5f);
glVertex3f(0.5f, 0.5f, 0.5f);
glVertex3f(0.5f, 0.5f, -0.5f);
glVertex3f(-0.5f, 0.5f, -0.5f);
glEnd();
glBegin(GL_QUADS);
// front
glColor3f(0.0f, 1.0f, 0.0f);
glNormal3f(0.0f, 0.0f, 1.0f);
glVertex3f(-0.5f, -0.5f, 0.5f);
glVertex3f(0.5f, -0.5f, 0.5f);
glVertex3f(0.5f, 0.5f, 0.5f);
glVertex3f(-0.5f, 0.5f, 0.5f);
glEnd();
glBegin(GL_QUADS);
// right
glColor3f(0.0f, 0.0f, 1.0f);
glNormal3f(1.0f, 0.0f, 0.0f);
glVertex3f(0.5f, -0.5f, 0.5f);
glVertex3f(0.5f, -0.5f, -0.5f);
glVertex3f(0.5f, 0.5f, -0.5f);
glVertex3f(0.5f, 0.5f, 0.5f);
glEnd();
glBegin(GL_QUADS);
// left
glColor3f(0.0f, 0.0f, 0.5f);
glNormal3f(-1.0f, 0.0f, 0.0f);
glVertex3f(-0.5f, -0.5f, 0.5f);
glVertex3f(-0.5f, 0.5f, 0.5f);
glVertex3f(-0.5f, 0.5f, -0.5f);
glVertex3f(-0.5f, -0.5f, -0.5f);
glEnd();
glBegin(GL_QUADS);
// bottom
glColor3f(0.5f, 0.0f, 0.0f);
glNormal3f(0.0f, -1.0f, 0.0f);
glVertex3f(-0.5f, -0.5f, 0.5f);
glVertex3f(0.5f, -0.5f, 0.5f);
glVertex3f(0.5f, -0.5f, -0.5f);
glVertex3f(-0.5f, -0.5f, -0.5f);
glEnd();
glBegin(GL_QUADS);
// back
glColor3f(0.0f, 0.5f, 0.0f);
glNormal3f(0.0f, 0.0f, -1.0f);
glVertex3f(0.5f, 0.5f, -0.5f);
glVertex3f(0.5f, -0.5f, -0.5f);
glVertex3f(-0.5f, -0.5f, -0.5f);
glVertex3f(-0.5f, 0.5f, -0.5f);
glEnd();
glFrontFace(GL_CCW) and glEnable(GL_CULL_FACE) are set! I don’t unterstand why the second example has mistakes, because there are also all Quads counterclockwise drawn! Please help me! I don’t understand why example 1 works and example 2 not!!!
Thanks in advange!
Mat!!!