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#include "glad/glad.h"
#include "shader.h"
#include <stdio.h>
#include <stdlib.h>
/**
* Simple method to read shaders from path and return a string
* containing the code. Function allocates memory which needs
* to be cleaned up
* @param path Path to shader GLSL file
* @return buf Contents of shader file as a string
*/
char* read_shader(char* path) {
FILE* file = fopen(path, "r");
fseek(file, 0, SEEK_END);
int file_size = ftell(file);
rewind(file);
char* buf = malloc(file_size);
fread(buf, file_size, 1, file);
return buf;
}
/**
* Compile some given shader code
* @param type The type of shader (GL_VERTEX_SHADER, GL_FRAGMENT_SHADER etc)
* @param code The string corresponding to the shader code
* @return shader The GLuint pointer to the compiled shader
*/
GLuint compile_shader(GLuint type, const char* code) {
GLuint shader = glCreateShader(type);
glShaderSource(shader, 1, &code, NULL);
glCompileShader(shader);
GLint out;
glGetShaderiv(shader, GL_COMPILE_STATUS, &out);
if (out == GL_FALSE) {
fprintf(stderr, "Failed to compile shader: %s", code);
exit(1);
}
return shader;
}
/*
* Given a vertex and fragment shader, link and compile a shader program,
* returning the GLuint pointing to that program
* @param vs The vertex shader string, usually returend from read_shader
* @param fs The fragment shader string, usually returend from read_shader
* @return shader_program The pointer to the compiled shader
*/
GLuint create_shader_program(const char* vs, const char* fs) {
GLuint shader_program = glCreateProgram();
GLuint vertex_shader = compile_shader(GL_VERTEX_SHADER, vs);
GLuint fragment_shader = compile_shader(GL_FRAGMENT_SHADER, fs);
glAttachShader(shader_program, fragment_shader);
glAttachShader(shader_program, vertex_shader);
glLinkProgram(shader_program);
return shader_program;
}
int shader_init(struct shader* shader) {
char* shaders[2] = { "shaders/fragment.glsl", "shaders/vertex.glsl" };
char* fragment_shader = read_shader(shaders[0]);
char* vertex_shader = read_shader(shaders[1]);
GLuint shader_program = create_shader_program(vertex_shader, fragment_shader);
free(vertex_shader);
free(fragment_shader);
shader->program = shader_program;
return 0;
}
int set_uniform_mat4(char* var, struct shader* shader, mat4 matrix) {
GLuint loc = glGetUniformLocation(shader->program, var);
if (loc == -1) {
fprintf(stderr, "Invalid var %s for get_uniform_mat4: Does not exist\n", var);
exit(1);
return -1;
}
glUniformMatrix4fv(loc, 1, GL_FALSE, (void*)matrix);
return 0;
}
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