lg_shader_progs.c File Reference

Functions
LG_ShaderProg	LG_ShaderProg_create (const char **vertex_shader_code, const char **fragment_shader_code, const char **geometry_shader_code, LG_VAP_params *params)
void	LG_ShaderProg_delete (LG_ShaderProg *shader_prog)
void	LG_ShaderProg_use (LG_ShaderProg *shader_prog, zboolean gl_checking)
char *	LG_ShaderProg_load_src_from_file (const char *path)
int	LG_ShaderProg_get_attrib_loc (LG_ShaderProg *shader_prog, const char *attrib_name)
int	LG_ShaderProg_get_uniform_loc (LG_ShaderProg *shader_prog, const char *uniform_name)
uint32_t	lg_compile_shader (int type, const char **shader_code)
void	lg_shader_info_log (uint32_t shader)
void	lg_shader_program_info_log (uint32_t shader_prog_id)
const char *	lg_shader_get_string_from_type (int type)

Detailed Description

 === Wrapper functions to more easily create and manage shader progs ===

 LG_VAP_params = Vertex Attrib Pointer params

Function Documentation

LG_ShaderProg_create()

LG_ShaderProg LG_ShaderProg_create	(	const char **	vertex_shader_code,
		const char **	fragment_shader_code,
		const char **	geometry_shader_code,
		LG_VAP_params *	params
	)

Create shader prog from vertex and fragment shader source code

Also set vertex attrib pointer params if params != NULL

Shader prog id set to LG_INVALID_SHADER_PROG_ID on error

Parameters

vertex_shader_code	GLSL source code
fragment_shader_code	GLSL source code
geometry_shader_code	GLSL source code, may be NULL
params	An array of LG_VAP_params, may be NULL - VAP stands for Vertex Attrib Pointer

Example code:

// Vertex shader
 
#version 310 es
precision highp float;
uniform mat4 u_mvp_matrix;
in vec4 a_position;
in lowp vec4 a_color;
out lowp vec4 v_color;
void main() {
   gl_Position = u_mvp_matrix * a_position;
   v_color = a_color;
}
 
// Fragment shader
 
#version 310 es
in lowp vec4 v_color;
out lowp vec4 fragColor;
void main()
{
   fragColor = v_color;
}
 
char *vert_shader[1], *frag_shader[1];
*vert_shader = LG_ShaderProg_load_src_from_file(lg_engine_shader("shader1.vert"));
*frag_shader = LG_ShaderProg_load_src_from_file(lg_engine_shader("shader1.frag"));
 
LG_VAP_params draw_params[] = {
   {0, "a_position", 3, GL_FLOAT, FALSE, sizeof(Vertex_rgba), (void *)0},
   {1, "a_color", 4, GL_UNSIGNED_BYTE, TRUE, sizeof(Vertex_rgba), (void *)offsetof(Vertex_rgba, r)},
   VAP_END
};
 
LG_ShaderProg shader_prog = LG_ShaderProg_create((const char **)vert_shader, (const char **)frag_shader, NULL, draw_params);

Returns

A new LG_ShaderProg

LG_ShaderProg_delete()

void LG_ShaderProg_delete

(

LG_ShaderProg *

shader_prog

)

Delete shader prog

Parameters

shader_prog

Addr of shader prog

LG_ShaderProg_use()

void LG_ShaderProg_use	(	LG_ShaderProg *	shader_prog,
		zboolean	gl_checking
	)

Use shader prog

Parameters

shader_prog	Addr of shader prog
gl_checking	Enable (TRUE) / disable (FALSE) GL checking

LG_ShaderProg_load_src_from_file()

char * LG_ShaderProg_load_src_from_file

(

const char *

path

)

Load shader source code (GLSL) from file

Path should be inside assets/

If not NULL, returned string must be freed afterwards

Example use:

char *src;
if ((src = LG_ShaderProg_load_src_from_file(lg_shader("mesh_shader1.vert"))) != NULL) {
   // Do something with src
   free3(src);
} else {
   INFO_ERR("Bla bla\n")
}

Parameters

path	GLSL file name, inside assets/

Returns

Pointer to a string containing GLSL source code if OK, NULL on error

LG_ShaderProg_get_attrib_loc()

int LG_ShaderProg_get_attrib_loc	(	LG_ShaderProg *	shader_prog,
		const char *	attrib_name
	)

Get the location of an attribute variable in the shader prog

Return -1 on error

From: https://docs.gl/es2/glGetAttribLocation
 
"If the named attribute variable is not an active attribute in the specified program object
or if name starts with the reserved prefix 'gl_', a value of -1 is returned."

Parameters

shader_prog
attrib_name

Returns

Attribute location, set to -1 on error

LG_ShaderProg_get_uniform_loc()

int LG_ShaderProg_get_uniform_loc	(	LG_ShaderProg *	shader_prog,
		const char *	uniform_name
	)

Get the location of a uniform variable in the shader prog

Return -1 on error

From: https://docs.gl/es2/glGetUniformLocation
 
"This function returns -1 if name does not correspond to an active uniform variable in program
or if name starts with the reserved prefix 'gl_'."

Parameters

shader_prog
uniform_name

Returns

Uniform location, set to -1 on error

lg_compile_shader()

uint32_t lg_compile_shader	(	int	type,
		const char **	shader_code
	)

Load and compile shader from source

Parameters

type	GL_VERTEX_SHADER, GL_FRAGMENT_SHADER, or GL_GEOMETRY_SHADER_OES
shader_code	GLSL source code

Returns

Shader or 0 on error

lg_shader_info_log()

void lg_shader_info_log

(

uint32_t

shader

)

Print out shader compilation log

Parameters

shader

lg_shader_program_info_log()

void lg_shader_program_info_log

(

uint32_t

shader_prog_id

)

Print out shader prog linking log

Parameters

shader_prog_id

lg_shader_get_string_from_type()

const char * lg_shader_get_string_from_type

(

int

type

)

Get shader string from type, ie

GL_VERTEX_SHADER       -> "vertex"
GL_FRAGMENT_SHADER     -> "fragment"
GL_GEOMETRY_SHADER_OES -> "geometry"
Another value          -> "<unknown type>"

Parameters

type

Returns

String