Graphics Reference
In-Depth Information
To query for the list of active uniforms in a program, you first call
glGetProgramiv
with the
GL_ACTIVE_UNIFORMS
parameter (as described
in the previous section). This will tell you the number of active uniforms
in the program. The list includes uniforms in named uniform blocks,
default block uniforms declared in shader code, and built-in uniforms
used in shader code. A uniform is considered “active” if it was used by
the program. In other words, if you declare a uniform in one of your
shaders but never use it, the linker will likely optimize that away and not
return it in the active uniform list. You can also find out the number of
characters (including the null terminator) that the largest uniform name
has in the program; this can be done by calling
glGetProgramiv
with the
GL_ACTIVE_UNIFORM_MAX_LENGTH
parameter.
Once we know the number of active uniforms and the number
of characters needed to store the uniform names, we can find
out the details on each uniform using
glGetActiveUniform
and
glGetActiveUniformsiv
.
void
glGetActiveUniform
(GLuint
program
, GLuint
index
,
GLsizei
bufSize
, GLsizei *
length
,
GLint *
size
, GLenum *
type
,
GLchar *
name
)
handle to the program object
program
the uniform index to be queried
index
the number of characters in the name array
bufSize
if not
NULL
, will be written with the number of characters
written into the name array (less the null terminator)
length
if the uniform variable being queried is an array, this
variable will be written with the maximum array element
used in the program (plus 1); if the uniform variable being
queried is not an array, this value will be 1
size
will be written with the uniform type; can be
GL_FLOAT, GL_FLOAT_VEC2, GL_FLOAT_VEC3,
GL_FLOAT_VEC4, GL_INT, GL_INT_VEC2, GL_INT_VEC3,
GL_INT_VEC4, GL_UNSIGNED_INT,
GL_UNSIGNED_INT_VEC2, GL_UNSIGNED_INT_VEC3,
GL_UNSIGNED_INT_VEC4, GL_BOOL, GL_BOOL_VEC2,
GL_BOOL_VEC3, GL_BOOL_VEC4, GL_FLOAT_MAT2,
(continues)
type
