OpenGL custom quads have lighting bugs

Question

I'm trying to figure out how to write my own primitives like gluSolidCube()..

In the following code I'm drawing 2 quads. One with the help of this method (the red one) and another one - by my own with the help of glBegin()/glEnd() (the blue one).

glPushMatrix();
    glRotatef(-angleX, 0, 0, 1);
    glRotatef(angleY, 0, 1, 0);

    glColor3f(1, 0, 0);
    glTranslatef(0.6, 0, 0);
    glutSolidCube(1);

    glColor3f(0, 0, 1);
    glTranslatef(-1.2, 0, 0);
    glPolygonMode(GL_FRONT, GL_FILL);
    glShadeModel(GL_SMOOTH);
    glBegin(GL_QUADS);
        glVertex3f(0.5, 0.5, 0.5);
        glVertex3f(0.5, 0.5, -0.5);
        glVertex3f(-0.5, 0.5, -0.5);
        glVertex3f(-0.5, 0.5, 0.5);

        glVertex3f(0.5, 0.5, 0.5);
        glVertex3f(0.5, 0.5, -0.5);
        glVertex3f(0.5, -0.5, -0.5);
        glVertex3f(0.5, -0.5, 0.5);

        glVertex3f(-0.5, 0.5, -0.5);
        glVertex3f(-0.5, 0.5, 0.5);
        glVertex3f(-0.5, -0.5, 0.5);
        glVertex3f(-0.5, -0.5, -0.5);

        glVertex3f(0.5, 0.5, -0.5);
        glVertex3f(-0.5, 0.5, -0.5);
        glVertex3f(-0.5, -0.5, -0.5);
        glVertex3f(0.5, -0.5, -0.5);

        glVertex3f(0.5, 0.5, 0.5);
        glVertex3f(-0.5, 0.5, 0.5);
        glVertex3f(-0.5, -0.5, 0.5);
        glVertex3f(0.5, -0.5, 0.5);

        glVertex3f(0.5, -0.5, 0.5);
        glVertex3f(0.5, -0.5, -0.5);
        glVertex3f(-0.5, -0.5, -0.5);
        glVertex3f(-0.5, -0.5, 0.5);
    glEnd();
glPopMatrix();

So as you can see at the following screenshots the lightnings on the red quad is correct unlike the blue one. How to solve this?

For the minimum code that you have provided, you need normals: http://gamedev.stackexchange.com/questions/50653/opengl-why-do-i-have-to-set-a-normal-with-glnormal/50656 — Amadeus, Sep 12 '16 at 16:31
@Amadeus this link didn't provide me with a solution. I tried to add before every glVertex() a glNormal(0, 0, 1) and it didn't help... — GV_FiQst, Sep 12 '16 at 17:06

score 1 · Answer 1 · edited May 23 '17 at 10:29

1

OpenGL fixed-function lighting won't work correctly without sensible vertex/face normals.

You need to supply some, perhaps via glNormal().

edited May 23 '17 at 10:29

Community

1
1

answered Sep 12 '16 at 16:52

genpfault

51,148
11
85
139

Ok as I understood I need to do more maths. For every plane I need to get a normal vector? Is there some equation for this? Gone googling... – GV_FiQst Sep 12 '16 at 17:02

OpenGL custom quads have lighting bugs

1 Answers1