Xcode 8 Beta 6 Opengl es template project error

Had the same issue. Was able to solve as follows:

When parameter value i == 0, UnsafeRawPointer(bitPattern: i) evaluates to nil, which you can't force unwrap.

Since the vertex position offset is 0, you can just pass nil as the last parameter:

glVertexAttribPointer(GLuint(GLKVertexAttrib.position.rawValue), 3, GLenum(GL_FLOAT), GLboolean(GL_FALSE), 24, nil)

Alternatively, you can change the BUFFER_OFFSET function to:

- 01. Return an optional

- 02. Don't force unwrap the UnsafeRawPointer call

func BUFFER_OFFSET(_ i: Int) -> UnsafeRawPointer? {
    return UnsafeRawPointer(bitPattern: i)
}

Woohoo! I can use the start project again 😝