OpenGL Screencast 14: textures part 1

014.c

#include "screencasts.h"

/*
 *  main()
 *  ----
 *  Start up GLUT and tell it what to do
 */
int main(int argc,char* argv[])
{
  initializeGlobals();
  /* screencast specific variables */
  windowName = "OpenGL screenscasts 14: Textures part 1";
  screencastID = 14;
  dim = 4;
  fov = 50;
  th = -25;
  ph = 15;
  ecX = -0.4;
  ecZ = -2.0;
  distance = 2;

  glutInit(&argc,argv);
  glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
  glutInitWindowSize(windowWidth,windowHeight);
  glutCreateWindow(windowName);

  glutDisplayFunc(display);
  glutReshapeFunc(displayReshape);
  glutKeyboardFunc(windowKey);
  glutSpecialFunc(windowSpecial);

  initializeTextures();

  redisplayAll();
  glutMainLoop();
  return 0;
}

draw.c

void drawScreencast14(void)
{
  drawLight();
  currentTexture = textures[TEX_CRATE];
  cube(0,0,0, 1,1,1, 0); 
}

globals.c

/*  TEXTURES  */
unsigned int textures[7];
int currentTexture=TEX_DEFAULT;

initialization.c

void initializeTextures(void)
{
  /*
    TEX_DEFAULT 0
    TEX_BRICK 1
    TEX_CRATE 2
    TEX_ICE 3
    TEX_FIRE 4
    TEX_EARTH 5
    TEX_WOOD 6
   */
  textures[TEX_BRICK] = loadTexBMP("txBrick14.bmp");
  textures[TEX_CRATE] = loadTexBMP("txCrate.bmp");
  textures[TEX_ICE] = loadTexBMP("txIce7.bmp");
  textures[TEX_FIRE] = loadTexBMP("txLava1.bmp");
  textures[TEX_EARTH] = loadTexBMP("txRock5.bmp");
  textures[TEX_WOOD] = loadTexBMP("txWood3.bmp");
}

Makefile

# Target to build
#TARGET = 011 012 013 014
TARGET = 014
#EXECS = ./011 ./012 ./013 ./014
EXECS = ./executables/014

# Libraries - LINUX
#LIBS=-lglut -lGLU
# Libraries - OSX
LIBS=-framework OpenGL -framework GLUT

all: $(TARGET)

# Generic compile rules
.c.o: 
	gcc -c -g -O -Wall $<

# Generic compile and link
%: %.c screencasts.a
	gcc -Wall -O3 -o ./executables/$@ $^ $(LIBS)

clean:
	rm -f $(EXECS) *.o *.a

# without .h => globals.o
screencasts.a:globals.o print.o error.o fatal.o textures.o shapes.o models.o interaction.o initialization.o draw.o display.o
	ar -rcs screencasts.a $^

shapes.c

void cube(double x,double y,double z,
	  double dx,double dy,double dz,
	  double th)
{
  /*  Cube vertices */
  GLfloat vertA[3] = { 0.5, 0.5, 0.5};
  GLfloat vertB[3] = {-0.5, 0.5, 0.5};
  GLfloat vertC[3] = {-0.5,-0.5, 0.5};
  GLfloat vertD[3] = { 0.5,-0.5, 0.5};
  GLfloat vertE[3] = { 0.5, 0.5,-0.5};
  GLfloat vertF[3] = {-0.5, 0.5,-0.5};
  GLfloat vertG[3] = {-0.5,-0.5,-0.5};
  GLfloat vertH[3] = { 0.5,-0.5,-0.5};

  glPushMatrix();
  /*  Transform */
  glTranslated(x,y,z);
  glRotated(th,0,1,0);
  glScaled(dx,dy,dz);

  glEnable(GL_TEXTURE_2D);
  /* using the current texture */
  glBindTexture(GL_TEXTURE_2D,currentTexture);

  /* Cube */
  glBegin(GL_QUADS);
  /* front => ABCD yellow */
  glNormal3f(0,0,1);
  if (screencastID < 14)
    glColor3f(1.0,1.0,0.0);
  glTexCoord2f(0,0); glVertex3fv(vertA);
  glTexCoord2f(1,0); glVertex3fv(vertB);
  glTexCoord2f(1,1); glVertex3fv(vertC);
  glTexCoord2f(0,1); glVertex3fv(vertD);
  glEnd();

  /* back => FEHG red */
  glBegin(GL_QUADS);
  glNormal3f(0,0,-1);
  if (screencastID < 14)
    glColor3f(1.0,0.0,0.0);
  glTexCoord2f(0,0); glVertex3fv(vertF);
  glTexCoord2f(1,0); glVertex3fv(vertE);
  glTexCoord2f(1,1); glVertex3fv(vertH);
  glTexCoord2f(0,1); glVertex3fv(vertG);
  //glEnd();
  //glBegin(GL_QUADS);
  /* right => EADH green */
  glNormal3f(1,0,0);
  //if (screencastID < 14)
  glColor3f(0.0,1.0,0.0);
  glTexCoord2f(0,0); glVertex3fv(vertE);
  glTexCoord2f(1,0); glVertex3fv(vertA);
  glTexCoord2f(1,1); glVertex3fv(vertD);
  glTexCoord2f(0,1); glVertex3fv(vertH);
  glEnd();
  glDisable(GL_TEXTURE_2D);

  glBegin(GL_QUADS);
  /* left => BFGC blue */
  glNormal3f(-1,0,0);
  if (screencastID < 14)
    glColor3f(0.0,0.0,1.0);
  glVertex3fv(vertB);
  glVertex3fv(vertF);
  glVertex3fv(vertG);
  glVertex3fv(vertC);
  /* top => EFBA turquoise */
  glNormal3f(0,1,0);
  if (screencastID < 14)
    glColor3f(0.0,1.0,1.0);
  glVertex3fv(vertE);
  glVertex3fv(vertF);
  glVertex3fv(vertB);
  glVertex3fv(vertA);
  /* bottom => DCGH pink */
  glNormal3f(0,-1,0);
  if (screencastID < 14)
    glColor3f(1.0,0.0,1.0);
  glVertex3fv(vertD);
  glVertex3fv(vertC);
  glVertex3fv(vertG);
  glVertex3fv(vertH);
  glEnd();

  glPopMatrix();
}

textures.c

#include "screencasts.h"

/*
 *  Reverse n bytes
 */
static void reverseBytes(void* x,const int n)
{
   int k;
   char* ch = (char*)x;
   for (k=0;k<n/2;k++)
   {
      char tmp = ch[k];
      ch[k] = ch[n-1-k];
      ch[n-1-k] = tmp;
   }
}

/*
 *  Load texture from BMP file
 */
unsigned int loadTexBMP(char* file)
{
  unsigned int   texture;    /* Texture name */
  FILE*          f;          /* File pointer */
  unsigned short magic;      /* Image magic */
  unsigned int   dx,dy,size; /* Image dimensions */
  unsigned short nbp,bpp;    /* Planes and bits per pixel */
  unsigned char* image;      /* Image data */
  unsigned int   k;          /* Counter */

  /*  Open file */
  f = fopen(file,"rb");
  if (!f) fatal("Cannot open file %s\n",file);
  /*  Check image magic */
  if (fread(&magic,2,1,f)!=1) fatal("Cannot read magic from %s\n",file);
  if (magic!=0x4D42 && magic!=0x424D) fatal("Image magic not BMP in %s\n",file);
  /*  Seek to and read header */
  if (fseek(f,16,SEEK_CUR) || fread(&dx ,4,1,f)!=1 || fread(&dy ,4,1,f)!=1 ||
      fread(&nbp,2,1,f)!=1 || fread(&bpp,2,1,f)!=1 || fread(&k,4,1,f)!=1)
    fatal("Cannot read header from %s\n",file);
  /*  Reverse bytes on big endian hardware (detected by backwards magic) */
  if (magic==0x424D) {
    reverseBytes(&dx,4);
    reverseBytes(&dy,4);
    reverseBytes(&nbp,2);
    reverseBytes(&bpp,2);
    reverseBytes(&k,4);
  }
  /*  Check image parameters */
  if (dx<1 || dx>65536) fatal("%s image width out of range: %d\n",file,dx);
  if (dy<1 || dy>65536) fatal("%s image height out of range: %d\n",file,dy);
  if (nbp!=1)  fatal("%s bit planes is not 1: %d\n",file,nbp);
  if (bpp!=24) fatal("%s bits per pixel is not 24: %d\n",file,bpp);
  if (k!=0)    fatal("%s compressed files not supported\n",file);
#ifndef GL_VERSION_2_0
  /*  OpenGL 2.0 lifts the restriction that texture size must be a power of two */
  for (k=1;k<dx;k*=2);
  if (k!=dx) fatal("%s image width not a power of two: %d\n",file,dx);
  for (k=1;k<dy;k*=2);
  if (k!=dy) fatal("%s image height not a power of two: %d\n",file,dy);
#endif

  /*  Allocate image memory */
  size = 3*dx*dy;
  image = (unsigned char*) malloc(size);
  if (!image) fatal("Cannot allocate %d bytes of memory for image %s\n",size,file);
  /*  Seek to and read image */
  if (fseek(f,20,SEEK_CUR) || fread(image,size,1,f)!=1) 
    fatal("Error reading data from image %s\n",file);
  fclose(f);
  /*  Reverse colors (BGR -> RGB) */
  for (k=0;k<size;k+=3) {
    unsigned char temp = image[k];
    image[k]   = image[k+2];
    image[k+2] = temp;
  }

  /*  Sanity check */
  errCheck("loadTexBMP");
  /*  Generate 2D texture */
  glGenTextures(1,&texture);
  glBindTexture(GL_TEXTURE_2D,texture);
  /*  Copy image */
  glTexImage2D(GL_TEXTURE_2D,0,3,dx,dy,0,GL_RGB,GL_UNSIGNED_BYTE,image);
  if (glGetError()) fatal("Error in glTexImage2D %s %dx%d\n",file,dx,dy);
  /*  Scale linearly when image size doesn't match */
  glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
  glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);

  /*  Free image memory */
  free(image);
  /*  Return texture name */
  return texture;
}