Shaders and Programmable Pipeline

Shaders and Programmable Pipeline — Fuctions for accessing the programmable GL pipeline

Synopsis

enum                CoglShaderType;
CoglHandle          cogl_create_shader                  (CoglShaderType shader_type);
gboolean            cogl_is_shader                      (CoglHandle handle);
void                cogl_shader_source                  (CoglHandle shader,
                                                         const char *source);
void                cogl_shader_compile                 (CoglHandle handle);
char *              cogl_shader_get_info_log            (CoglHandle handle);
CoglShaderType      cogl_shader_get_type                (CoglHandle handle);
gboolean            cogl_shader_is_compiled             (CoglHandle handle);

CoglHandle          cogl_create_program                 (void);
gboolean            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_name);
void                cogl_program_set_uniform_1f         (CoglHandle program,
                                                         int uniform_location,
                                                         float value);
void                cogl_program_set_uniform_1i         (CoglHandle program,
                                                         int uniform_location,
                                                         int value);
void                cogl_program_set_uniform_float      (CoglHandle program,
                                                         int uniform_location,
                                                         int n_components,
                                                         int count,
                                                         const float *value);
void                cogl_program_set_uniform_int        (CoglHandle program,
                                                         int uniform_location,
                                                         int n_components,
                                                         int count,
                                                         const int *value);
void                cogl_program_set_uniform_matrix     (CoglHandle program,
                                                         int uniform_location,
                                                         int dimensions,
                                                         int count,
                                                         gboolean transpose,
                                                         const float *value);

Description

COGL allows accessing the GL programmable pipeline in order to create vertex and fragment shaders.

The only supported format is GLSL shaders.

Details

enum CoglShaderType

typedef enum {
  COGL_SHADER_TYPE_VERTEX,
  COGL_SHADER_TYPE_FRAGMENT
} CoglShaderType;

Types of shaders

COGL_SHADER_TYPE_VERTEX

A program for proccessing vertices

COGL_SHADER_TYPE_FRAGMENT

A program for processing fragments

Since 1.0


cogl_create_shader ()

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.

shader_type :

COGL_SHADER_TYPE_VERTEX or COGL_SHADER_TYPE_FRAGMENT.

Returns :

a new shader handle.

cogl_is_shader ()

gboolean            cogl_is_shader                      (CoglHandle handle);

Gets whether the given handle references an existing shader object.

handle :

A CoglHandle

Returns :

TRUE if the handle references a shader, FALSE otherwise

cogl_shader_source ()

void                cogl_shader_source                  (CoglHandle shader,
                                                         const char *source);

Replaces the current GLSL source associated with a shader with a new one.

shader :

CoglHandle for a shader.

source :

GLSL shader source.

cogl_shader_compile ()

void                cogl_shader_compile                 (CoglHandle handle);

Compiles the shader, no return value, but the shader is now ready for linking into a program.

handle :

CoglHandle for a shader.

cogl_shader_get_info_log ()

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() to retrieve the compiler warnings/error messages that caused a shader to not compile correctly, mainly useful for debugging purposes.

handle :

CoglHandle for a shader.

Returns :

a newly allocated string containing the info log. Use g_free() to free it

cogl_shader_get_type ()

CoglShaderType      cogl_shader_get_type                (CoglHandle handle);

Retrieves the type of a shader CoglHandle

handle :

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

cogl_shader_is_compiled ()

gboolean            cogl_shader_is_compiled             (CoglHandle handle);

Retrieves whether a shader CoglHandle has been compiled

handle :

CoglHandle for a shader.

Returns :

TRUE if the shader object has sucessfully be compiled

cogl_create_program ()

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.

cogl_is_program ()

gboolean            cogl_is_program                     (CoglHandle handle);

Gets whether the given handle references an existing program object.

handle :

A CoglHandle

Returns :

TRUE if the handle references a program, FALSE otherwise

cogl_program_attach_shader ()

void                cogl_program_attach_shader          (CoglHandle program_handle,
                                                         CoglHandle shader_handle);

Attaches a shader to a program object, a program can have one vertex shader and one fragment shader attached.

program_handle :

a CoglHandle for a shdaer program.

shader_handle :

a CoglHandle for a vertex of fragment shader.

cogl_program_link ()

void                cogl_program_link                   (CoglHandle handle);

Links a program making it ready for use.

handle :

a CoglHandle for a shader program.

cogl_program_get_uniform_location ()

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.

handle :

a CoglHandle for a shader program.

uniform_name :

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.

cogl_program_set_uniform_1f ()

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.

program :

A CoglHandle for a linked program

uniform_location :

the uniform location retrieved from cogl_program_get_uniform_location().

value :

the new value of the uniform.

Since 1.4


cogl_program_set_uniform_1i ()

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.

program :

A CoglHandle for a linked program

uniform_location :

the uniform location retrieved from cogl_program_get_uniform_location().

value :

the new value of the uniform.

Since 1.4


cogl_program_set_uniform_float ()

void                cogl_program_set_uniform_float      (CoglHandle program,
                                                         int uniform_location,
                                                         int n_components,
                                                         int count,
                                                         const float *value);

Changes the value of a float vector uniform, or uniform array for the given linked program.

program :

A CoglHandle for a linked program

uniform_location :

the uniform location retrieved from cogl_program_get_uniform_location().

n_components :

The number of components for the uniform. For example with glsl you'd use 3 for a vec3 or 4 for a vec4.

count :

For uniform arrays this is the array length otherwise just pass 1

value :

the new value of the uniform[s]. [array length=count]

Since 1.4


cogl_program_set_uniform_int ()

void                cogl_program_set_uniform_int        (CoglHandle program,
                                                         int uniform_location,
                                                         int n_components,
                                                         int count,
                                                         const int *value);

Changes the value of a int vector uniform, or uniform array for the given linked program.

program :

A CoglHandle for a linked program

uniform_location :

the uniform location retrieved from cogl_program_get_uniform_location().

n_components :

The number of components for the uniform. For example with glsl you'd use 3 for a vec3 or 4 for a vec4.

count :

For uniform arrays this is the array length otherwise just pass 1

value :

the new value of the uniform[s]. [array length=count]

Since 1.4


cogl_program_set_uniform_matrix ()

void                cogl_program_set_uniform_matrix     (CoglHandle program,
                                                         int uniform_location,
                                                         int dimensions,
                                                         int count,
                                                         gboolean transpose,
                                                         const float *value);

Changes the value of a matrix uniform, or uniform array in the given linked program.

program :

A CoglHandle for a linked program

uniform_location :

the uniform location retrieved from cogl_program_get_uniform_location().

dimensions :

The dimensions of the matrix. So for for example pass 2 for a 2x2 matrix or 3 for 3x3.

count :

For uniform arrays this is the array length otherwise just pass 1

transpose :

Whether to transpose the matrix when setting the uniform.

value :

the new value of the uniform. [array length=count]

Since 1.4