Problems in OpenGL ES

[abhimanipal]

Hi everybody I am trying to write my first open gl es app and I have run into a road block. The objective of this exercise is to draw a line between 2 points

This is my code

	glEnableVertexAttribArray(GLKVertexAttribPosition);
	glVertexAttribPointer(GLKVertexAttribPosition,
						  2,              // Two components per vertex
						  GL_FLOAT,
						  GL_FALSE,
						  0,              // Stride
						  myMagicVertices);
	glDrawArrays(
				 GL_LINE_STRIP,
				 0,              // Start Index
				 2);             // Number of vertices to read
	glDisableVertexAttribArray(GLKVertexAttribPosition);

However I am getting an error when I compile the code. The error is GLKVertexAttribPosition is not defined. I have included the following header files in my .h file

#import <OpenGLES/EAGL.h>
#import <OpenGLES/ES2/gl.h>
#import <OpenGLES/ES2/glext.h>
#import <OpenGLES/EAGLDrawable.h>

What am I doing wrong here

[Duncan C]

Originally Posted by abhimanipal

Hi everybody I am trying to write my first open gl es app and I have run into a road block. The objective of this exercise is to draw a line between 2 points

This is my code

	glEnableVertexAttribArray(GLKVertexAttribPosition);
	glVertexAttribPointer(GLKVertexAttribPosition,
						  2,              // Two components per vertex
						  GL_FLOAT,
						  GL_FALSE,
						  0,              // Stride
						  myMagicVertices);
	glDrawArrays(
				 GL_LINE_STRIP,
				 0,              // Start Index
				 2);             // Number of vertices to read
	glDisableVertexAttribArray(GLKVertexAttribPosition);

However I am getting an error when I compile the code. The error is GLKVertexAttribPosition is not defined. I have included the following header files in my .h file

#import <OpenGLES/EAGL.h>
#import <OpenGLES/ES2/gl.h>
#import <OpenGLES/ES2/glext.h>
#import <OpenGLES/EAGLDrawable.h>

What am I doing wrong here

Oh boy. OpenGL ES 2.0 is gnarly stuff. I suggest finding a good book on the subject.

I always have to look this stuff up myself.

I have only just started using GLKit, so I don't know it well. At first I thought your use of the constant GLKVertexAttribPosition was flat wrong. However, I see that it is defined in GLKit.h.

I'm too tired right now to verify that that constant is what you want, but it's defined in GLKit.h, so you should add that #import:

#import <GLKit/GLKit.h>

I suspect that you actually want the constant GLKVertexAttrib, (or the standard OpenGL constant ATTRIB_VERTEX) but I might be wrong. Like I said, I'm too tired to figure it out right now.