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/**
* Utilities for OpenGL shading language
*
* Brian Paul
* 9 April 2008
*/
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <GL/glew.h>
#include <GL/glut.h>
#include "shaderutil.h"
static void
Init(void)
{
static GLboolean firstCall = GL_TRUE;
if (firstCall) {
firstCall = GL_FALSE;
}
}
GLboolean
ShadersSupported(void)
{
const char *version = (const char *) glGetString(GL_VERSION);
if (version[0] == '2' && version[1] == '.') {
return GL_TRUE;
}
else if (glutExtensionSupported("GL_ARB_vertex_shader")
&& glutExtensionSupported("GL_ARB_fragment_shader")
&& glutExtensionSupported("GL_ARB_shader_objects")) {
fprintf(stderr, "Warning: Trying ARB GLSL instead of OpenGL 2.x. This may not work.\n");
return GL_TRUE;
}
return GL_TRUE;
}
GLuint
CompileShaderText(GLenum shaderType, const char *text)
{
GLuint shader;
GLint stat;
Init();
shader = glCreateShader(shaderType);
glShaderSource(shader, 1, (const GLchar **) &text, NULL);
glCompileShader(shader);
glGetShaderiv(shader, GL_COMPILE_STATUS, &stat);
if (!stat) {
GLchar log[1000];
GLsizei len;
glGetShaderInfoLog(shader, 1000, &len, log);
fprintf(stderr, "Error: problem compiling shader: %s\n", log);
exit(1);
}
else {
/*printf("Shader compiled OK\n");*/
}
return shader;
}
/**
* Read a shader from a file.
*/
GLuint
CompileShaderFile(GLenum shaderType, const char *filename)
{
const int max = 100*1000;
int n;
char *buffer = (char*) malloc(max);
GLuint shader;
FILE *f;
Init();
f = fopen(filename, "r");
if (!f) {
fprintf(stderr, "Unable to open shader file %s\n", filename);
return 0;
}
n = fread(buffer, 1, max, f);
/*printf("read %d bytes from shader file %s\n", n, filename);*/
if (n > 0) {
buffer[n] = 0;
shader = CompileShaderText(shaderType, buffer);
}
else {
return 0;
}
fclose(f);
free(buffer);
return shader;
}
GLuint
LinkShaders(GLuint vertShader, GLuint fragShader)
{
GLuint program = glCreateProgram();
assert(vertShader || fragShader);
if (fragShader)
glAttachShader(program, fragShader);
if (vertShader)
glAttachShader(program, vertShader);
glLinkProgram(program);
/* check link */
{
GLint stat;
glGetProgramiv(program, GL_LINK_STATUS, &stat);
if (!stat) {
GLchar log[1000];
GLsizei len;
glGetProgramInfoLog(program, 1000, &len, log);
fprintf(stderr, "Shader link error:\n%s\n", log);
return 0;
}
}
return program;
}
void
InitUniforms(GLuint program, struct uniform_info uniforms[])
{
GLuint i;
for (i = 0; uniforms[i].name; i++) {
uniforms[i].location
= glGetUniformLocation(program, uniforms[i].name);
printf("Uniform %s location: %d\n", uniforms[i].name,
uniforms[i].location);
switch (uniforms[i].size) {
case 1:
if (uniforms[i].type == GL_INT)
glUniform1i(uniforms[i].location,
(GLint) uniforms[i].value[0]);
else
glUniform1fv(uniforms[i].location, 1, uniforms[i].value);
break;
case 2:
glUniform2fv(uniforms[i].location, 1, uniforms[i].value);
break;
case 3:
glUniform3fv(uniforms[i].location, 1, uniforms[i].value);
break;
case 4:
glUniform4fv(uniforms[i].location, 1, uniforms[i].value);
break;
default:
abort();
}
}
}
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