• class PPMpixmap
  {
   public:
   //methods:
   PPMpixmap();      //constructor, which initializes maxColors to 256, nRows, nCols to 0
   ~PPMpixmap();     //destructor
   int readPPMfile(string filename);//opens filename (returns 0 if unable to open file), reads and assigns values to inRows, nCols, maxColors, and pixel. Returns 1 if successful.
   //data:
   int nRows, nCols; //dimension of the image
   int maxColors;    //maximum number of shades each color (r,g,b)
   Color3 *pixel     //dynamic array of pixels
  }

The code for readPPMfile is found in our files directory.
      

• class TextureInfo
  {
   public:
   //methods:
   void setWhich(int which);
   void setFrame(GLdouble l, GLdouble r, GLdouble b, GLdouble t);
   void setImage(GLint w, GLint h);
  
   //data:
   int whichone, width, height;
   GLdouble frame_left, frame_right, frame_bottom, frame_top, frame_width, frame_height;
  }
  

• add these data fields to class Object:

  bool isTextured; //default is false, set in the constructor
  TextureInfo texture;

Scene:

• Add data member:
    PPMpixmap image[15]; //list of image pixel maps
  
  
• Add to readScene:
  if (identifier == "IMAGES")
  {
    infile>>identifier;
    while(identifier!="ENDIMAGES")
    {
      image[numImages].readPPMfile(identifier);
      numImages++;
      infile>>identifier;
    }
  }
  
  
• Add to readScene, within the BEGIN and END,
  if (identifier == "texture")
  {
    obj[i].isTextured = true;
      infile>>which;  //local integer variable
    obj[i].texture.setWhich(which);
    infile>>left>>right>>bottom>>top; //local GLdouble variables
    obj[i].texture.setFrame(left, right, bottom, top);
  }
  
  
• Add code to shade method so that it renders textured surfaces:

  Set up local Color3 variables for diffuse and ambient.
  After calculating phong,
       Assign diffuse and ambient to be the object's material diffuse and ambient. If the object is not textured, these will not change.
       If the object is textured,
       {
             if the object is a square or a plane
             {
                 set the generic hit point, GH
                 if G>H is within the texture frame
                 {
                    set local variable j to be which texture;
                    set local variables for numColors, nCols and nRows //these locals are set merely for convenience;
                    calculate which row (tex_row) and which column (tex_col) of the image map the pixel is in;
                    calculate and assign whichpix to be the correct entry for this pixel (tex_col, tex_row) of the image array, which is one-dimensional;
                    assign local variable diffuse to be the red, green, blue components in this array entry, divided by the number of colors;
                    assign local variable ambient to be the diffuse values * 0.3 (or some other appropriate fraction)
                 }
              }
       }

  Then continue on with lighting calculations as before.

Test Files:

All files are located in /classes/cs3114/Advanced_Graphics/files/texture directory. The ones I used in class today for demo are there, along with the appropriate PPM files:

• tex1.scn
• tex2.scn
• tex3.scn
• tex4.scn
• ts.scn
• wood.ppm
• sunrise.ppm
• dog.ppm
• shingle.ppm