progs/util/shaderutil.c

   1 /**
   2  * Utilities for OpenGL shading language
   3  *
   4  * Brian Paul
   5  * 9 April 2008
   6  */
   7
   8
   9 #include <stdio.h>
  10 #include <stdlib.h>
  11 #include <GL/glut.h>
  12 #include "extfuncs.h"
  13 #include "shaderutil.h"
  14
  15
  16 static void
  17 Init(void)
  18 {
  19    static GLboolean firstCall = GL_TRUE;
  20    if (firstCall) {
  21       GetExtensionFuncs();
  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_func(shaderType);
  53    glShaderSource_func(shader, 1, (const GLchar **) &text, NULL);
  54    glCompileShader_func(shader);
  55    glGetShaderiv_func(shader, GL_COMPILE_STATUS, &stat);
  56    if (!stat) {
  57       GLchar log[1000];
  58       GLsizei len;
  59       glGetShaderInfoLog_func(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
  81    FILE *f = fopen(filename, "r");
  82    if (!f) {
  83       fprintf(stderr, "Unable to open shader file %s\n", filename);
  84       return 0;
  85    }
  86
  87    n = fread(buffer, 1, max, f);
  88    /*printf("read %d bytes from shader file %s\n", n, filename);*/
  89    if (n > 0) {
  90       buffer[n] = 0;
  91       shader = CompileShaderText(shaderType, buffer);
  92    }
  93    else {
  94       return 0;
  95    }
  96
  97    fclose(f);
  98    free(buffer);
  99
 100    return shader;
 101 }
 102
 103
 104 GLuint
 105 LinkShaders(GLuint vertShader, GLuint fragShader)
 106 {
 107    GLuint program = glCreateProgram_func();
 108
 109    glAttachShader_func(program, fragShader);
 110    glAttachShader_func(program, vertShader);
 111    glLinkProgram_func(program);
 112
 113    /* check link */
 114    {
 115       GLint stat;
 116       glGetProgramiv_func(program, GL_LINK_STATUS, &stat);
 117       if (!stat) {
 118          GLchar log[1000];
 119          GLsizei len;
 120          glGetProgramInfoLog_func(program, 1000, &len, log);
 121          fprintf(stderr, "Shader link error:\n%s\n", log);
 122          return 0;
 123       }
 124    }
 125
 126    return program;
 127 }
 128
 129
 130 void
 131 InitUniforms(GLuint program, struct uniform_info uniforms[])
 132 {
 133    GLuint i;
 134
 135    for (i = 0; uniforms[i].name; i++) {
 136       uniforms[i].location
 137          = glGetUniformLocation_func(program, uniforms[i].name);
 138
 139       printf("Uniform %s location: %d\n", uniforms[i].name,
 140              uniforms[i].location);
 141
 142       switch (uniforms[i].size) {
 143       case 1:
 144          if (uniforms[i].type == GL_INT)
 145             glUniform1i_func(uniforms[i].location,
 146                              (GLint) uniforms[i].value[0]);
 147          else
 148             glUniform1fv_func(uniforms[i].location, 1, uniforms[i].value);
 149          break;
 150       case 2:
 151          glUniform2fv_func(uniforms[i].location, 1, uniforms[i].value);
 152          break;
 153       case 3:
 154          glUniform3fv_func(uniforms[i].location, 1, uniforms[i].value);
 155          break;
 156       case 4:
 157          glUniform4fv_func(uniforms[i].location, 1, uniforms[i].value);
 158          break;
 159       default:
 160          abort();
 161       }
 162    }
 163 }