214 CHAPTER 7: Well-Rendered Miscellany^
cy=(frame.size.height/2.0);centerRelative=CGPointMake(m_PointerLocation.x-cx,cy-m_PointerLocation.y);
//2
[[OpenGLCreateTexture getObject]renderTextureAt:centerRelative name:m_FlareSource
size:3.0 r:1.0 g:1.0 b:1.0 a:1.0];
//3
[m_LensFlare execute:[[UIScreen mainScreen]applicationFrame]
source:m_PointerLocation];
}
I put the helper routines for creating and rendering a texture on their own module,
renderTextureAt(), which is covered in Listing 7-6. However, there are three lines to
take note of:
Lines 1ff get the center of the screen and creates the information
needed to track the flare source (the sun) with the pointer.
In line 2, the flare’s source object, usually the sun, is rendered.
Line 3 calls the helper routine that draws our 2D sun graphic in
the sky.
Listing 7-6. Rendering a 2D texture-(void)renderTextureAt:(CGPoint)position name:(GLuint)name
size:(GLfloat)size r:(GLfloat)r g:(GLfloat)g b:(GLfloat)b a:(GLfloat)a; //1
{
float scaledX,scaledY;
GLfloat zoomBias=.1;
GLfloat scaledSize;static const GLfloat squareVertices[] =
{
-1.0, -1.0, 0.0,
1.0, -1.0, 0.0,
-1.0, 1.0, 0.0,
1.0, 1.0, 0.0,
};static GLfloat textureCoords[] =
{
0.0, 0.0,
1.0, 0.0,
0.0, 1.0,
1.0, 1.0
};CGRect frame = [[UIScreen mainScreen] bounds];
float aspectRatio=frame.size.height/frame.size.width;scaledX=2.0*position.x/frame.size.width; //2
scaledY=2.0*position.y/frame.size.height;glDisable(GL_DEPTH_TEST); //3