progs/util/shaderutil.c

   1 /**
   2  * Utilities for OpenGL shading language
   3  *
   4  * Brian Paul
   5  * 9 April 2008
   6  */
   7
   8
   9 #include <assert.h>
  10 #include <stdio.h>
  11 #include <stdlib.h>
  12 #include <GL/glew.h>
  13 #include <GL/glut.h>
  14 #include "shaderutil.h"
  15
  16
  17 static void
  18 Init(void)
  19 {
  20    static GLboolean firstCall = GL_TRUE;
  21    if (firstCall) {
  22       firstCall = GL_FALSE;
  23    }
  24 }
  25
  26
  27 GLboolean
  28 ShadersSupported(void)
  29 {
  30    const char *version = (const char *) glGetString(GL_VERSION);
  31    if (version[0] == '2' && version[1] == '.') {
  32       return GL_TRUE;
  33    }
  34    else if (glutExtensionSupported("GL_ARB_vertex_shader")
  35             && glutExtensionSupported("GL_ARB_fragment_shader")
  36             && glutExtensionSupported("GL_ARB_shader_objects")) {
  37       fprintf(stderr, "Warning: Trying ARB GLSL instead of OpenGL 2.x.  This may not work.\n");
  38       return GL_TRUE;
  39    }
  40    return GL_TRUE;
  41 }
  42
  43
  44 GLuint
  45 CompileShaderText(GLenum shaderType, const char *text)
  46 {
  47    GLuint shader;
  48    GLint stat;
  49
  50    Init();
  51
  52    shader = glCreateShader(shaderType);
  53    glShaderSource(shader, 1, (const GLchar **) &text, NULL);
  54    glCompileShader(shader);
  55    glGetShaderiv(shader, GL_COMPILE_STATUS, &stat);
  56    if (!stat) {
  57       GLchar log[1000];
  58       GLsizei len;
  59       glGetShaderInfoLog(shader, 1000, &len, log);
  60       fprintf(stderr, "Error: problem compiling shader: %s\n", log);
  61       exit(1);
  62    }
  63    else {
  64       /*printf("Shader compiled OK\n");*/
  65    }
  66    return shader;
  67 }
  68
  69
  70 /**
  71  * Read a shader from a file.
  72  */
  73 GLuint
  74 CompileShaderFile(GLenum shaderType, const char *filename)
  75 {
  76    const int max = 100*1000;
  77    int n;
  78    char *buffer = (char*) malloc(max);
  79    GLuint shader;
  80    FILE *f;
  81
  82    Init();
  83
  84
  85    f = fopen(filename, "r");
  86    if (!f) {
  87       fprintf(stderr, "Unable to open shader file %s\n", filename);
  88       return 0;
  89    }
  90
  91    n = fread(buffer, 1, max, f);
  92    /*printf("read %d bytes from shader file %s\n", n, filename);*/
  93    if (n > 0) {
  94       buffer[n] = 0;
  95       shader = CompileShaderText(shaderType, buffer);
  96    }
  97    else {
  98       return 0;
  99    }
 100
 101    fclose(f);
 102    free(buffer);
 103
 104    return shader;
 105 }
 106
 107
 108 GLuint
 109 LinkShaders(GLuint vertShader, GLuint fragShader)
 110 {
 111    GLuint program = glCreateProgram();
 112
 113    assert(vertShader || fragShader);
 114
 115    if (fragShader)
 116       glAttachShader(program, fragShader);
 117    if (vertShader)
 118       glAttachShader(program, vertShader);
 119    glLinkProgram(program);
 120
 121    /* check link */
 122    {
 123       GLint stat;
 124       glGetProgramiv(program, GL_LINK_STATUS, &stat);
 125       if (!stat) {
 126          GLchar log[1000];
 127          GLsizei len;
 128          glGetProgramInfoLog(program, 1000, &len, log);
 129          fprintf(stderr, "Shader link error:\n%s\n", log);
 130          return 0;
 131       }
 132    }
 133
 134    return program;
 135 }
 136
 137
 138 void
 139 InitUniforms(GLuint program, struct uniform_info uniforms[])
 140 {
 141    GLuint i;
 142
 143    for (i = 0; uniforms[i].name; i++) {
 144       uniforms[i].location
 145          = glGetUniformLocation(program, uniforms[i].name);
 146
 147       printf("Uniform %s location: %d\n", uniforms[i].name,
 148              uniforms[i].location);
 149
 150       switch (uniforms[i].size) {
 151       case 1:
 152          if (uniforms[i].type == GL_INT)
 153             glUniform1i(uniforms[i].location,
 154                              (GLint) uniforms[i].value[0]);
 155          else
 156             glUniform1fv(uniforms[i].location, 1, uniforms[i].value);
 157          break;
 158       case 2:
 159          glUniform2fv(uniforms[i].location, 1, uniforms[i].value);
 160          break;
 161       case 3:
 162          glUniform3fv(uniforms[i].location, 1, uniforms[i].value);
 163          break;
 164       case 4:
 165          glUniform4fv(uniforms[i].location, 1, uniforms[i].value);
 166          break;
 167       default:
 168          abort();
 169       }
 170    }
 171 }