opengl-es - How can GLKit draw triangles using both CW or CCW notation?

Question

I have a simple textured quad (composed of 2 triangles) that im rendering in my iPhone app using GLKit.

Now for some reason I am not seeing any difference when defining my vertices with CW notation vs CCW notation. Why is this? Note that I am using the default GLKit project template with minimal changes. Also, I am using the GLKBaseEffect for rendering, not ES2.

Answer 1

对于四边形，CW 与 CCW 改变了法线——三角形的哪一侧“向上”。默认情况下禁用面剔除glEnable(GL_CULL_FACE)（用于启用它），因此“向上”或“向下”三角形都将被渲染。