OpenGL ES Texture Not Rendering - ios

Question

I am attempting to render a texture to a plane with OpenGL ES on an iPhone. I have worked with OpenGL before but I'm not sure why this isn't working.
When I run the code the plane is rendered as a black square and not a textured square. I believe the problem may be when loading the texture although I see no errors when I run the code.
Hopefully someone will spot a problem and be able to help. Thanks in advance.
Here is my code for the mesh.
// Mesh loading
- ( id ) init {
if ( self = [ super init ] ) {
glGenVertexArraysOES( 1, &m_vertexArray );
glBindVertexArrayOES( m_vertexArray );
glGenBuffers( 1, &m_vertexBuffer );
glBindBuffer( GL_ARRAY_BUFFER, m_vertexBuffer );
glBufferData( GL_ARRAY_BUFFER, sizeof( g_vertices ), g_vertices, GL_STATIC_DRAW );
glGenBuffers( 1, &m_texCoordBuffer );
glBindBuffer( GL_ARRAY_BUFFER, m_texCoordBuffer );
glBufferData( GL_ARRAY_BUFFER, sizeof( g_texCoords ), g_texCoords, GL_STATIC_DRAW );
}
return self;
}
- ( void ) render {
glBindBuffer( GL_ARRAY_BUFFER, m_vertexBuffer );
glVertexAttribPointer( GLKVertexAttribPosition, 3, GL_FLOAT, GL_FALSE, 0, ( GLvoid* ) 0 );
glBindBuffer( GL_ARRAY_BUFFER, m_texCoordBuffer );
glVertexAttribPointer( GLKVertexAttribTexCoord0, 2, GL_FLOAT, GL_FALSE, 0, ( GLvoid* ) 0 );
glDrawArrays( GL_TRIANGLES, 0, sizeof( g_vertices ) / sizeof( g_vertices[ 0 ] ) );
}
const GLfloat g_vertices[] = {
-1.0, -1.0, 0.0,
1.0, 1.0, 0.0,
-1.0, 1.0, 0.0,
-1.0, -1.0, 0.0,
1.0, -1.0, 0.0,
1.0, 1.0, 0.0
};
const GLfloat g_texCoords[] = {
0.0, 0.0,
1.0, 1.0,
0.0, 1.0,
0.0, 0.0,
1.0, 0.0,
1.0, 1.0
};
I only need a my vertices and tex coords right now so that is all I'm using.
Next is my texture loading.
- ( id ) init: ( NSString* ) filename {
if ( self = [ super init ] ) {
CGImageRef spriteImage = [ UIImage imageNamed: filename ].CGImage;
if ( !spriteImage ) {
NSLog( #"Failed to load image %#", filename );
exit( 1 );
}
size_t width = CGImageGetWidth( spriteImage );
size_t height = CGImageGetHeight( spriteImage );
GLubyte *spriteData = ( GLubyte* ) calloc( width * height * 4, sizeof( GLubyte ) );
CGContextRef spriteContext = CGBitmapContextCreate( spriteData, width, height, 8, 4 * width, CGImageGetColorSpace( spriteImage ), kCGImageAlphaPremultipliedLast );
CGContextDrawImage( spriteContext, CGRectMake( 0, 0, width, height ), spriteImage );
CGContextRelease( spriteContext );
glGenTextures( 1, &m_texture );
glBindTexture( GL_TEXTURE_2D, m_texture );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST );
glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA, ( GLuint ) width, ( GLuint ) height, 0, GL_RGBA, GL_UNSIGNED_BYTE, spriteData );
free( spriteData );
}
return self;
}
- ( void ) bind {
glActiveTexture( GL_TEXTURE0 );
glBindTexture( GL_TEXTURE_2D, m_texture );
}
I used the texture loading code from this tutorial.
Then here is my rendering code.
- ( void ) glkView: ( GLKView* ) view drawInRect: ( CGRect ) rect {
glClearColor( 0.65f, 0.65f, 0.65f, 1.0f );
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
glUseProgram( m_shaderProgram );
[ m_texture bind ];
glUniform1i( uniforms[ UNIFORM_SAMPLER ], 0 );
GLKMatrix4 mvp = GLKMatrix4Multiply( GLKMatrix4Multiply( m_projectionMatrix, m_viewMatrix ), m_modelMatrix );
glUniformMatrix4fv( uniforms[ UNIFORM_MODELVIEWPROJECTION_MATRIX ], 1, 0, mvp.m );
glEnableVertexAttribArray( GLKVertexAttribPosition );
glEnableVertexAttribArray( GLKVertexAttribTexCoord0 );
[ m_plane render ];
glDisableVertexAttribArray( GLKVertexAttribTexCoord0 );
glDisableVertexAttribArray( GLKVertexAttribPosition );
}
Vertex shader.
attribute vec3 position;
attribute vec2 texCoord;
varying lowp vec2 texCoord0;
uniform mat4 modelViewProjectionMatrix;
void main()
{
texCoord0 = texCoord;
gl_Position = modelViewProjectionMatrix * vec4( position, 1.0 );
}
And lastly fragment shader.
varying lowp vec2 texCoord0;
uniform sampler2D sampler;
void main()
{
gl_FragColor = texture2D( sampler, texCoord0.st );
}

Answer 1

As mentioned in the comment, you can check with a Power of Two (POT) texture. In addition, there are extensions that enable support for NonPOT (NPOT) textures like GL_IMG_texture_npot, refer to the discussion in this thread (Non power of two textures in iOS), and this thread (http://aras-p.info/blog/2012/10/17/non-power-of-two-textures/).