tutorial: teapot.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <GL/glew.h>
#include <GL/glut.h>
#include "trackball.h"

GLuint program;

static const GLchar * vertex_shader[] ={"\
varying vec3 normal, lightDir;\
uniform mat4 RotationMatrix;  \
uniform float Zoom;\
void main()\
{          \
  lightDir=normalize(vec3(gl_LightSource[0].position)); \
  vec4 n = RotationMatrix*vec4(gl_NormalMatrix*gl_Normal, 1);\
  normal=normalize(n.xyz);         \
  gl_Position = gl_ProjectionMatrix * RotationMatrix \
   * gl_ModelViewMatrix*vec4(Zoom*gl_Vertex.xyz, 1.0); \
}"};

static const GLchar * fragment_shader[] ={"\
/* simple toon fragment shader */\
/* www.lighthouse3d.com        */\
\
varying vec3 normal, lightDir;\
\
void main()\
{\
        float intensity;\
        vec3 n;\
        vec4 color;\
\
        n = normalize(normal);\
        intensity = max(dot(lightDir,n),0.0);\
        if (intensity > 0.98)\
                color = vec4(0.8,0.8,0.8,1.0);\
        else if (intensity > 0.5)\
                color = vec4(0.4,0.4,0.8,1.0);\
        else if (intensity > 0.25)\
                color = vec4(0.2,0.2,0.4,1.0);\
        else\
                color = vec4(0.1,0.1,0.1,1.0);\
        gl_FragColor = color;\
}"};

void create_shaders()
{
  GLuint v, f;

  v = glCreateShader(GL_VERTEX_SHADER);
  f = glCreateShader(GL_FRAGMENT_SHADER);
  glShaderSource(v, 1, vertex_shader, NULL);
  glShaderSource(f, 1, fragment_shader, NULL);
  glCompileShader(v);
  GLint compiled;
  glGetShaderiv(v, GL_COMPILE_STATUS, &compiled );
  if ( !compiled ) {
    GLsizei  maxLength, length;
    glGetShaderiv( v, GL_INFO_LOG_LENGTH, &maxLength );
    GLchar* log = malloc(sizeof(GLchar)*(maxLength+1));
    glGetShaderInfoLog(v,  maxLength, &length, log);
    printf("Vertex Shader compilation failed: %s\n", log);
    free(log);
  }
  glCompileShader(f);
  glGetShaderiv(f, GL_COMPILE_STATUS, &compiled );
  if ( !compiled ) {
    GLsizei  maxLength, length;
    glGetShaderiv( f, GL_INFO_LOG_LENGTH, &maxLength );
    GLchar* log = malloc(sizeof(GLchar)*(maxLength+1));
    glGetShaderInfoLog(f,  maxLength, &length, log);
    printf("Fragment Shader compilation failed: %s\n", log);
    free(log);
  }
  program = glCreateProgram();
  glAttachShader(program, f);
  glAttachShader(program, v);
  glLinkProgram(program);
  GLint linked;
  glGetProgramiv(program, GL_LINK_STATUS, &linked );
  if ( !linked ) {
    GLsizei len;
    glGetProgramiv(program, GL_INFO_LOG_LENGTH, &len );
    GLchar* log = malloc(sizeof(GLchar)*(len+1));
    glGetProgramInfoLog(program, len, &len, log );
    printf("Shader linking failed: %s\n", log);
    free(log);
  }
  glUseProgram(program);
}


float lpos[4] = {1, 0.5, 1, 0};
GLfloat m[4][4]; // modelview rotation matrix
float last[4], cur[4]; // rotation tracking quaternions 
int width, height, beginx, beginy;
float p1x, p1y, p2x, p2y;
float zoom = 1.0;

void display(void)
{
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  glLightfv(GL_LIGHT0, GL_POSITION, lpos);
  GLuint location = glGetUniformLocation(program, "RotationMatrix");
  build_rotmatrix(m, cur);  
  if( location >= 0 )
    glUniformMatrix4fv(location, 1, GL_FALSE, &m[0][0]);
  location = glGetUniformLocation(program, "Zoom");
  if (location >= 0) glUniform1f(location, zoom);
  glutSolidTeapot(0.6);
  glutSwapBuffers();
}

void reshape (int w, int h)
{
  double l = 1;
  width=w;  height=h;
  glViewport (0, 0, w, h);
  glMatrixMode (GL_PROJECTION);
  glLoadIdentity();
  glOrtho(-l, l, -l, l, -l, l);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
}

void keys(unsigned char key, int x, int y)
{
   if (key == 27 || key == 'q') 
         exit(0);
}

void mouse(int button,int state, int x, int y)   
{
  beginx = x;
  beginy = y;
  if (button == 3 && state == GLUT_DOWN)
    { zoom *= 1.1; glutPostRedisplay(); }
  else if (button == 4 && state == GLUT_DOWN)
    { zoom /= 1.1; glutPostRedisplay(); }
}

void motion(int x,int y)   
{
  p1x = (2.0*beginx - width)/width;
  p1y = (height - 2.0*beginy)/height;
  p2x = (2.0 * x - width) / width;
  p2y = (height - 2.0 * y) / height;
  trackball(last, p1x, p1y, p2x, p2y);   
  add_quats(last, cur, cur);   
  beginx = x;
  beginy = y;
  glutPostRedisplay();   
}

int main(int argc, char **argv)
{
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);
  glutInitWindowSize(512, 512);
  glutInitWindowPosition((glutGet(GLUT_SCREEN_WIDTH)-512)/2,
                         (glutGet(GLUT_SCREEN_HEIGHT)-512)/2);
  glutCreateWindow("Use mouse to rotate");
  
  trackball(cur, 0.0, 0.0, 0.0, 0.0);

  glutDisplayFunc(display);
  glutReshapeFunc(reshape);
  glutMouseFunc(mouse);
  glutMotionFunc(motion);
  glutKeyboardFunc(keys);

  glEnable(GL_DEPTH_TEST);
  glClearColor(1.0,1.0,1.0,1.0);
  glewInit();
  if (!glewIsSupported("GL_VERSION_2_0"))
   {
     printf("GLSL not supported\n");
     exit(EXIT_FAILURE);
   }
  create_shaders();
  glutMainLoop();
  return EXIT_SUCCESS;
}