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Cogl Reference Manual | ![]() |
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Top | Description |
Shaders and Programmable PipelineShaders and Programmable Pipeline — Fuctions for accessing the programmable GL pipeline |
enum CoglShaderType; CoglHandle cogl_create_shader (CoglShaderType shader_type
);CoglBool cogl_is_shader (CoglHandle handle
);void cogl_shader_source (CoglHandle shader
,const
);char *sourcevoid cogl_shader_compile (CoglHandle handle
);char * cogl_shader_get_info_log (CoglHandle handle
); CoglShaderType cogl_shader_get_type (CoglHandle handle
);CoglBool cogl_shader_is_compiled (CoglHandle handle
); CoglHandle cogl_create_program (void
);CoglBool cogl_is_program (CoglHandle handle
);void cogl_program_attach_shader (CoglHandle program_handle
,CoglHandle shader_handle
);void cogl_program_link (CoglHandle handle
);int cogl_program_get_uniform_location (CoglHandle handle
,const
);char *uniform_namevoid cogl_program_set_uniform_1f (CoglHandle program
,,
int uniform_location);
float valuevoid cogl_program_set_uniform_1i (CoglHandle program
,,
int uniform_location);
int valuevoid cogl_program_set_uniform_float (CoglHandle program
,,
int uniform_location,
int n_components,
int countconst
);float *valuevoid cogl_program_set_uniform_int (CoglHandle program
,,
int uniform_location,
int n_components,
int countconst
);int *valuevoid cogl_program_set_uniform_matrix (CoglHandle program
,,
int uniform_location,
int dimensions,
int count,
CoglBool transposeconst
);float *value
Cogl allows accessing the GL programmable pipeline in order to create vertex and fragment shaders.
The shader source code can either be GLSL or ARBfp. If the source
code is ARBfp, it must begin with the string “!!ARBfp1.0”. The
application should check for the COGL_FEATURE_SHADERS_GLSL
or
COGL_FEATURE_SHADERS_ARBFP
features before using shaders.
When using GLSL Cogl provides replacement names for most of the builtin varyings and uniforms. It is recommended to use these names wherever possible to increase portability between OpenGL 2.0 and GLES 2.0. GLES 2.0 does not have most of the builtins under their original names so they will only work with the Cogl names.
For use in all GLSL shaders, the Cogl builtins are as follows:
The current modelview matrix. This is equivalent to
The current projection matrix. This is equivalent to
The combined modelview and projection matrix. A vertex shader
would typically use this to transform the incoming vertex
position. The separate modelview and projection matrices are
usually only needed for lighting calculations. This is
equivalent to
An array of matrices for transforming the texture
coordinates. This is equivalent to
In a vertex shader, the following are also available:
The incoming vertex position. This is equivalent to
The incoming vertex color. This is equivalent to
The texture coordinate for the first texture unit. This is
equivalent to
The texture coordinate for the first texture unit. This is
equivalent to
The normal of the vertex. This is equivalent to
The calculated position of the vertex. This must be written to
in all vertex shaders. This is equivalent to
The calculated size of a point. This is equivalent to
The calculated color of a vertex. This is equivalent to
An array of calculated texture coordinates for a vertex. This is
equivalent to
In a fragment shader, the following are also available:
The calculated color of a vertex. This is equivalent to
An array of calculated texture coordinates for a vertex. This is
equivalent to
The final calculated color of the fragment. All fragment shaders
must write to this variable. This is equivalent to
An optional output variable specifying the depth value to use
for this fragment. This is equivalent to
A readonly variable that will be true if the current primitive
is front facing. This can be used to implement two-sided
coloring algorithms. This is equivalent to
It's worth nothing that this API isn't what Cogl would like to have
in the long term and it may be removed in Cogl 2.0. The
experimental
typedef enum { COGL_SHADER_TYPE_VERTEX, COGL_SHADER_TYPE_FRAGMENT } CoglShaderType;
Types of shaders
A program for proccessing vertices | |
A program for processing fragments |
Since 1.0
CoglHandle cogl_create_shader (CoglShaderType shader_type
);
Create a new shader handle, use cogl_shader_source()
to set the
source code to be used on it.
|
COGL_SHADER_TYPE_VERTEX or COGL_SHADER_TYPE_FRAGMENT. |
Returns : |
a new shader handle. |
CoglBool cogl_is_shader (CoglHandle handle
);
Gets whether the given handle references an existing shader object.
|
A CoglHandle |
Returns : |
TRUE FALSE |
void cogl_shader_source (CoglHandle shader
,const
);char *source
Replaces the current source associated with a shader with a new one.
Please see above for a description of the recommended format for the shader code.
|
CoglHandle for a shader. |
|
Shader source. |
void cogl_shader_compile (CoglHandle handle
);
Compiles the shader, no return value, but the shader is now ready for linking into a program. Note that calling this function is optional. If it is not called then the shader will be automatically compiled when it is linked.
|
CoglHandle for a shader. |
char * cogl_shader_get_info_log (CoglHandle handle
);
Retrieves the information log for a coglobject, can be used in conjunction
with cogl_shader_get_parameteriv()
|
CoglHandle for a shader. |
Returns : |
a newly allocated string containing the info log. Use
g_free() |
CoglShaderType cogl_shader_get_type (CoglHandle handle
);
Retrieves the type of a shader CoglHandle
|
CoglHandle for a shader. |
Returns : |
COGL_SHADER_TYPE_VERTEX if the shader is a vertex processor
or COGL_SHADER_TYPE_FRAGMENT if the shader is a frament processor |
CoglBool cogl_shader_is_compiled (CoglHandle handle
);
Retrieves whether a shader CoglHandle has been compiled
|
CoglHandle for a shader. |
Returns : |
TRUE |
CoglHandle cogl_create_program (void
);
Create a new cogl program object that can be used to replace parts of the GL rendering pipeline with custom code.
Returns : |
a new cogl program. |
CoglBool cogl_is_program (CoglHandle handle
);
Gets whether the given handle references an existing program object.
|
A CoglHandle |
Returns : |
TRUE FALSE |
void cogl_program_attach_shader (CoglHandle program_handle
,CoglHandle shader_handle
);
Attaches a shader to a program object. A program can have multiple
vertex or fragment shaders but only one of them may provide a
main()
|
a CoglHandle for a shdaer program. |
|
a CoglHandle for a vertex of fragment shader. |
void cogl_program_link (CoglHandle handle
);
Links a program making it ready for use. Note that calling this function is optional. If it is not called the program will automatically be linked the first time it is used.
|
a CoglHandle for a shader program. |
int cogl_program_get_uniform_location (CoglHandle handle
,const
);char *uniform_name
Retrieve the location (offset) of a uniform variable in a shader program, a uniform is a variable that is constant for all vertices/fragments for a shader object and is possible to modify as an external parameter.
|
a CoglHandle for a shader program. |
|
the name of a uniform. |
Returns : |
the offset of a uniform in a specified program.
This uniform can be set using cogl_program_uniform_1f() when the
program is in use. |
void cogl_program_set_uniform_1f (CoglHandle program
,,
int uniform_location);
float value
Changes the value of a floating point uniform for the given linked
program
.
|
A CoglHandle for a linked program |
|
the uniform location retrieved from
cogl_program_get_uniform_location() . |
|
the new value of the uniform. |
Since 1.4
void cogl_program_set_uniform_1i (CoglHandle program
,,
int uniform_location);
int value
Changes the value of an integer uniform for the given linked
program
.
|
A CoglHandle for a linked program |
|
the uniform location retrieved from
cogl_program_get_uniform_location() . |
|
the new value of the uniform. |
Since 1.4
void cogl_program_set_uniform_float (CoglHandle program
,,
int uniform_location,
int n_components,
int countconst
);float *value
Changes the value of a float vector uniform, or uniform array for
the given linked program
.
|
A CoglHandle for a linked program |
|
the uniform location retrieved from
cogl_program_get_uniform_location() . |
|
The number of components for the uniform. For example with glsl you'd use 3 for a vec3 or 4 for a vec4. |
|
For uniform arrays this is the array length otherwise just pass 1 |
|
the new value of the uniform[s]. [array length=count] |
Since 1.4
void cogl_program_set_uniform_int (CoglHandle program
,,
int uniform_location,
int n_components,
int countconst
);int *value
Changes the value of a int vector uniform, or uniform array for
the given linked program
.
|
A CoglHandle for a linked program |
|
the uniform location retrieved from
cogl_program_get_uniform_location() . |
|
The number of components for the uniform. For example with glsl you'd use 3 for a vec3 or 4 for a vec4. |
|
For uniform arrays this is the array length otherwise just pass 1 |
|
the new value of the uniform[s]. [array length=count] |
Since 1.4
void cogl_program_set_uniform_matrix (CoglHandle program
,,
int uniform_location,
int dimensions,
int count,
CoglBool transposeconst
);float *value
Changes the value of a matrix uniform, or uniform array in the
given linked program
.
|
A CoglHandle for a linked program |
|
the uniform location retrieved from
cogl_program_get_uniform_location() . |
|
The dimensions of the matrix. So for for example pass 2 for a 2x2 matrix or 3 for 3x3. |
|
For uniform arrays this is the array length otherwise just pass 1 |
|
Whether to transpose the matrix when setting the uniform. |
|
the new value of the uniform. [array length=count] |
Since 1.4