ios - How to use glVertexAttribPointer function in Swift 3? -

when working buffers , vertex attributes in opengl es (3.0) , objective-c use

glbufferdata(gl_array_buffer, sizeof(attributes), attributes, gl_dynamic_draw); 

to load vertex data (attributes) buffer, , then

glenablevertexattribarray(0); glvertexattribpointer(0, sizeof(vertexcoordinatesstruct) / sizeof(glfloat), gl_float, gl_false, sizeof(vertexattributesstruct), 0);  glenablevertexattribarray(1); glvertexattribpointer(1, sizeof(texturecoordinatesstruct) / sizeof(glfloat), gl_float, gl_false, sizeof(vertexattributesstruct), (void *)sizeof(vertexcoordinatesstruct)); 

to specify vertex data memory layout in buffer vertex shader. notice how cast sizeof(oglvertexcoordinates) void* in second glvertexattribpointer call. if offset in gl_array_buffer @ texturecoordinatesstruct data lying.

and i'm trying implement same exact type of code in swift 3. glvertexattribpointer function takes unsaferawpointer last parameter, not void*.

and problem can't solve: i'm unable create unsaferawpointer specific value (memory offset) can in objc.

i've studied q/a find, of them aren't suitable case or don't work in swift 3.

have checked opengl es game template of xcode?

(tested in xcode 8.1 gm seed.)

in gameviewcontroller.swift, can find this:

    glenablevertexattribarray(gluint(glkvertexattrib.position.rawvalue))     glvertexattribpointer(gluint(glkvertexattrib.position.rawvalue), 3, glenum(gl_float), glboolean(gl_false), 24, buffer_offset(0))     glenablevertexattribarray(gluint(glkvertexattrib.normal.rawvalue))     glvertexattribpointer(gluint(glkvertexattrib.normal.rawvalue), 3, glenum(gl_float), glboolean(gl_false), 24, buffer_offset(12)) 

and buffer_offset(_:) (in objective-c template, it's macro) defined as:

func buffer_offset(_ i: int) -> unsaferawpointer {     return unsaferawpointer(bitpattern: i)! } 

unfortunately, buggy , causes runtime crash. need fix to:

func buffer_offset(_ i: int) -> unsaferawpointer? {     return unsaferawpointer(bitpattern: i) } 

with buffer_offset(_:) can create unsaferawpointer specific value.