Graphics Reference
In-Depth Information
Example 3-5
Creating an EGL Pixel Buffer
(continued)
case EGL_BAD_PARAMETER:
// Verify that EGL_WIDTH and EGL_HEIGHT are
// non-negative values
break;
case EGL_BAD_MATCH:
// Check window and EGLConfig attributes to determine
// compatibility and pbuffer-texture parameters
break;
}
}
// Check the size of pbuffer that was allocated
EGLint width;
EGLint height;
if ( !eglQuerySurface ( display, pbuffer, EGL_WIDTH, &width ) ||
!eglQuerySurface ( display, pbuffer, EGL_HEIGHT, &height ))
{
// Unable to query surface information
}
Pbuffers support all OpenGL ES 3.0 rendering facilities, just as windows
do. The major difference—aside from the fact that you cannot display a
pbuffer on the screen—is that instead of swapping buffers when you are
finished rendering as you do with a window, you either copy the values
from a pbuffer to your application or modify the binding of the pbuffer as
a texture.
A rendering context is a data structure internal to OpenGL ES 3.0 that
contains all of the state information required for operation. For example,
it contains references to the vertex and fragment shaders and the array of
vertex data used in the example program in Chapter 2, “Hello Triangle:
An OpenGL ES 3.0 Example.” Before OpenGL ES 3.0 can draw, it needs to
have a context available for its use.
