Problems with simple cube and normals

OpenGL OpenGL: Basic Coding
1

Hi!

I have a problem with specifying the normals for a simple cube.
My vertices look like this:


std::vector<GLfloat> vertices =
{
 0.0f,0.0f,0.0f, 1.0f,0.0f,0.0f, 1.0f,1.0f,0.0f, 0.0f,1.0f,0.0f, //front
 0.0f,0.0f,1.0f, 1.0f,0.0f,1.0f, 1.0f,1.0f,1.0f, 0.0f,1.0f,1.0f, //back
 0.0f,0.0f,0.0f, 0.0f,0.0f,1.0f, 0.0f,1.0f,1.0f, 0.0f,1.0f,0.0f, //left
 1.0f,0.0f,0.0f, 1.0f,0.0f,1.0f, 1.0f,1.0f,1.0f, 1.0f,1.0f,0.0f, //right
 0.0f,0.0f,0.0f, 1.0f,0.0f,0.0f, 1.0f,0.0f,1.0f, 0.0f,0.0f,1.0f, //bottom
 0.0f,1.0f,0.0f, 1.0f,1.0f,0.0f, 1.0f,1.0f,1.0f, 0.0f,1.0f,1.0f  //top
 };

and my normals:


std::vector<GLfloat> normals =
{
 0.0f,0.0f,1.0f, 0.0f,0.0f,1.0f,  0.0f,0.0f,1.0f, 0.0f,0.0f,1.0f,
 0.0f,0.0f,-1.0f, 0.0f,0.0f,-1.0f,  0.0f,0.0f,-1.0f, 0.0f,0.0f,-1.0f,
 -1.0f,0.0f,0.0f, -1.0f,0.0f,0.0f, -1.0f,0.0f,0.0f, -1.0f,0.0f,0.0f,
 1.0f,0.0f,0.0f, 1.0f,0.0f,0.0f, 1.0f,0.0f,0.0f, 1.0f,0.0f,0.0f,
 0.0f,-1.0f,0.0f, 0.0f,-1.0f,0.0f, 0.0f,-1.0f,0.0f, 0.0f,-1.0f,0.0f,
 0.0f,1.0f,0.0f, 0.0f,1.0f,0.0f, 0.0f,1.0f,0.0f, 0.0f,1.0f,0.0f
};

Everything is packed in a vbo and is drawn by
glDrawArrays(GL_QUADS,0,24). The cube looks alright, but the left and right
side stays dark. The same code for drawing works without problems when i
import obj-files from blender. So there must be something wrong
with the normals. Any ideas?

2

OpenGL uses a right handed coordinate system (at least for the fixed function pipeline), so if x points to the right, y up, then z points towards you - in your image z points away from you.
The result is that you specify the left and right sides with different winding and you end up looking at the back faces.

3

God damm. I could cry. Your are right, error is fixed. Cost me
3 hours :wink:

Thx