Lecture1/5: 2D Animation, Project 1

• Make your scanLineSegment() deals with both texture mapping and directly coloring

        Pixel(Y + vReso/2, X + hReso/2) = texture? texture->Pixel(col[0], col[1]) : col;
  

• FillAnnulus()

  An annulus is defined by its center position, together with inner and outer radius. A circle is a special annulus with inner radius of 0.

  You can make your draw solid circle (either with texture mapping or not) in Canvas class more general, so this time it draw a general annulus.

  void FillAnnulus(int cx, int cy,  float r1, float r2,  int angularReso, int radianReso);
  

• How to generate ordered filenames

        ostringstream os;
        os << setfill('0') << setw(4) << i;
        canvas.filename = "frame" + os.str() + ".ppm";
  

  You need these header files: iostream, sstream and iomanip.

• Add Canvas :: Clear(RGB const& clear_color)

  You need this to clear the canvas before drawing the next frame.

• Animate a rotating circle

• Animate a translating and bouncing circle

      const int frames = 200;
      const int radius = 20;
      const int x0 = -canvas.hReso/2 + radius;
      const int y0 = -canvas.vReso/2 + radius;
      int step_x = 5;
      int step_y = 7;
      
      int x = x0, y = y0;
      
      for(int i = 0; i<frames; i++)
      {
        ostringstream os;
        os << setfill('0') << setw(4) << i;
        canvas.filename = "frame" + os.str() + ".ppm";
  
        canvas.Clear(Blue);
        canvas.SolidCircle(x, y, radius, Magenta);
        canvas.WritePPM();
        
        // update circle's center: (x, y)  
        x += step_x, y += step_y;
        if(x + radius >= canvas.hReso/2)                                         // move out of right boundary
        {
          x = canvas.hReso / 2 - 1 - 2 * (x+radius - canvas.hReso/2) - radius;   // bounce back
          step_x = - step_x;                                                     // will move left
        }
        else if(x - radius < -canvas.hReso/2)                                    // move out of left boundary
        {
          x = -canvas.hReso/2 + 2 * (-canvas.hReso/2 - (x - radius)) + radius;   // bounce back
          step_x = - step_x;                                                     // will move right
        }
        
        if(y + radius >= canvas.vReso/2)                                         // move out of upper boundary
        {
          y = canvas.vReso / 2 -1 - 2 * (y+radius - canvas.vReso/2) - radius;    // bounce back
          step_y = - step_y;                                                     // will move down
        }
        else if(y - radius < -canvas.vReso/2)                                    // move out of bottom boundary
        {
          y = -canvas.vReso/2 + 2 * (-canvas.vReso/2 - (y - radius)) + radius;   // bounce back
          step_y = - step_y;                                                     // will move up. 
        }
      }
  

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