Graphics Reference
In-Depth Information
If the shader compiles successfully, a new shader object is returned that
will be attached to the program later. The details of these shader object
functions are covered in the first sections of Chapter 4, “Shaders and
Programs.”
the Shaders
Once the application has created a shader object for the vertex and
fragment shaders, it needs to create a program object. Conceptually, the
program object can be thought of as the final linked program. Once the
various shaders are compiled into a shader object, they must be attached
to a program object and linked together before drawing.
The process of creating program objects and linking is fully described in
Chapter 4, “Shaders and Programs.” For now, we provide a brief overview
of the process. The first step is to create the program object and attach the
vertex shader and fragment shader to it.
// Create the program object
programObject = glCreateProgram();
if(programObject == 0)
return 0;
glAttachShader(programObject, vertexShader);
glAttachShader(programObject, fragmentShader);
Finally, we are ready to link the program and check for errors:
// Link the program
glLinkProgram(programObject);
// Check the link status
glGetProgramiv(programObject, GL_LINK_STATUS, &1inked);
if(!linked)
{
GLint infoLen = 0;
glGetProgramiv(programObject, GL_INFO_LOG_LENGTH,&infoLen);
if(infoLen > 1)
{
