CS 450/550 -- Fall Quarter 2022

Project #2

100 Points

Due: October 11

This page was last updated: September 10, 2022

Introduction

James Bond has a very special Vertical Take Off and Landing (VTOL) Cessna that is custom-fitted with helicopter-ish propellers to halp him get away from the Spectre bad guys without needing to have a runway. This project is to animate it and look at it in two different 3D views.

Requirements:

1. Draw a Cessna airplane. (Don't worry -- this won't be as hard as it sounds.)

2. The Cessna's 3 propellers must be positioned properly.
   The Cessna's 3 propellers must be scaled properly.
   The Cessna's 3 propellers must be oriented properly.
   The Cessna's 3 propellers must be rotating properly.

3. Allow two views: an "Outside" view of the entire scene and an "Inside" view from the Cessna cockpit. Be able to switch between them in your video. (You could use a pop-up menu or keyboard hits.) For each view, use a different call to gluLookAt( ) to position the eye.
   Hint: A good eye poition for your Inside View is (0., 1.2, 1.) .
   Hint: A good look-at position for your Inside View is (0., 5., 10.) .
   Feel free to change these as long as you can show us that a view out the front (+Z) of the cockpit works.

4. Keep the same Xrot, Yrot, and Scale features as we've used before, but only in the Outside View. Do not use Xrot, Yrot, and Scale in the Inside View.

5. Use gluPerspective( ), not glOrtho( ).

6. Put some sort of 3D scene for your Inside view to see, looking outside the Cessna (off in the +Z direction). One or more GLUT wireframe objects might work well. Or, whatever you did in the first project. Or some sort of colored grid. Or, all of these things.

7. Use the graphics programming strategy where the Display( ) function looks at a collection of global variables and draws the scene correctly. The other parts of the program simply set the global variables and post a redisplay.

8. The code for creating the Cessna geometry is shown below in the Geometry section. The Cessna body extends along the Z axis. The cockpit points in +Z.

9. There must be three propellers drawn on the Cessna body:
   1. A large propeller in the front, oriented in the X-Y plane. This should be located at (0.,0.,7.5) and have a radius of 5.
   2. A smaller propeller on the top of the left wing, oriented in the X-Z plane. This should be located at (-10.f, 3.f, 0.) and have a radius of 3. It is OK to leave out the axle that connects this propeller to the wing.
   3. A smaller propeller on the top of the right wing, oriented in the X-Z plane. This should be located at (10.f, 3.f, 0.) and have a radius of 3. It is OK to leave out the axle that connects this propeller to the wing.

   The smaller propellers must rotate twice as fast as the front propeller.

   The two smaller propellers must rotate in opposite directions.

10. Create a single propeller display list and then transform and instance it three times to get the three propellers in the scene. The code for creating the single propeller geometry is shown below in the Geometry section. The single propeller is in the X-Y plane, centered at (0.,0.,0.), with a radius of 1.0.

11. Pay close attention to the overall transformation sequence. You can re-use some of the transformations that you have already created by using glPushMatrix( ) and glPopMatrix( ).

12. Parameterize your scene as much as you can with #define's or const's, It makes it easier to make changes later.

13. Use GLUT pop-up menus for all options.

Positioning Everything:

• Remember how we did it in class: write down in words what you want to happen and then program it backwards.

• For the Cessna, you might have a word-transformation sequence like this:
  1. If you are in the Outside view, apply the Xrot, Yrot, and Scale transformations as before.
  2. Assign a good eye, look, and up position with gluLookAt.
  Then draw the Cessna.

• For the front propeller, you might have a word-transformation sequence like this:
  1. Scale the propeller to be the right size.
  2. Rotate the propeller to be in its proper orientation.
  3. Rotate the propeller by its current spinning rotation angle.
  4. Translate the propeller to where it needs to be on the Cessna.
  5. If you are in the Outside view, apply the Xrot, Yrot, and Scale transformations as before.
  6. Assign a good eye, look, and up position with gluLookAt.
  Then draw the propeller.

  and so on.

Supplying the Geometry

• Click here to get the file called cessna.550. Move it into your project workspace directory and then #include it in your C/C++ code just after your list of global variables.

• The cessna.550 file has the structure definitions in it, so you won't need to define them yourself.

• If you want to draw a wireframe Cessna, use the following code when you create your Cessna display list:

  int i;
  struct edge *ep;
  struct point *p0, *p1;
  
  glPushMatrix( );
  glRotatef(-7., 0., 1., 0.);
  glTranslatef( 0., -1., 0. );
  glRotatef(  97.,   0., 1., 0. );
  glRotatef( -15.,   0., 0., 1. );
  glBegin( GL_LINES );
  	for( i=0, ep = CESSNAedges; i < CESSNAnedges; i++, ep++ )
  	{
  		p0 = &CESSNApoints[ ep->p0 ];
  		p1 = &CESSNApoints[ ep->p1 ];
  		glVertex3f( p0->x, p0->y, p0->z );
  		glVertex3f( p1->x, p1->y, p1->z );
  	}
  glEnd( );
  glPopMatrix( );
  

• If you want to draw a polygon Cessna, use the following code when you create your Cessna display list:

  int i;
  struct point *p0, *p1, *p2;
  struct tri *tp;
  float p01[3], p02[3], n[3];
  
  glPushMatrix( );
  glRotatef(-7., 0., 1., 0.);
  glTranslatef( 0., -1., 0. );
  glRotatef(  97.,   0., 1., 0. );
  glRotatef( -15.,   0., 0., 1. );
  glBegin( GL_TRIANGLES );
  	for( i=0, tp = CESSNAtris; i < CESSNAntris; i++, tp++ )
  	{
  		p0 = &CESSNApoints[ tp->p0 ];
  		p1 = &CESSNApoints[ tp->p1 ];
  		p2 = &CESSNApoints[ tp->p2 ];
  
  		// fake "lighting" from above:
  
  		p01[0] = p1->x - p0->x;
  		p01[1] = p1->y - p0->y;
  		p01[2] = p1->z - p0->z;
  		p02[0] = p2->x - p0->x;
  		p02[1] = p2->y - p0->y;
  		p02[2] = p2->z - p0->z;
  		Cross( p01, p02, n );
  		Unit( n, n );
  		n[1] = fabs( n[1] );
  		glColor3f( n[1], .5f*n[1], 0. );
  
  		glVertex3f( p0->x, p0->y, p0->z );
  		glVertex3f( p1->x, p1->y, p1->z );
  		glVertex3f( p2->x, p2->y, p2->z );
  	}
  glEnd( );
  glPopMatrix( );
  

  In the glColor3f( ) call, take whatever R, G, B triple you want the Cessna to have and scale them all by n[1]. In the above example, James Bond wanted an orange Cessna.

• To create the single propeller, from which all three propellers will be instanced, use the following code when you create your propeller display list:

  // propeller parameters:
  
  #define PROPELLER_RADIUS	 1.0
  #define PROPELLER_WIDTH		 0.4
  
  // draw the cessna propeller with radius PROPELLER_RADIUS and
  //	width PROPELLER_WIDTH centered at (0.,0.,0.) in the XY plane
  
  glBegin( GL_TRIANGLES );
  	glVertex2f(  PROPELLER_RADIUS,  PROPELLER_WIDTH/2. );
  	glVertex2f(  0., 0. );
  	glVertex2f(  PROPELLER_RADIUS, -PROPELLER_WIDTH/2. );
  
  	glVertex2f( -PROPELLER_RADIUS, -PROPELLER_WIDTH/2. );
  	glVertex2f(  0., 0. );
  	glVertex2f( -PROPELLER_RADIUS,  PROPELLER_WIDTH/2. );
  glEnd( );
  

Getting Started:

Not sure where to start? Read on!

1. Draw the Cessna at the origin.

2. Draw at least one other scene element somewhere out along +Z. This is where the Inside View will be looking.

3. Start by using the stationary Outside View to view the scene. Give gluLookAt( ) some good values.

   Play with these so that when your program starts up, your are seeing the Cessna and your whole scene from a good angle.

4. Pay careful attention to:
   • Make the near clipping plane location very small, e.g., 0.1
   • Make the far clipping plane location big-ish (not huge), e.g., 1000.
   • Be sure to set some non-BLACK color right before drawing things.
   • Be careful how far the eye is from the Cessna. Too close and you might get the Cessna clipped off. Too far and the Cessna will look like a little fly speck.

5. After that works, designate Animate( ) as the Idle Function in InitGraphics( ). Have a global variable, say BladeAngle, that gets incremented in Animate( ). Use that variable in Display( ) to rotate the propellers. Be sure that Animate( ) posts a re-display.

6. A way that I really like to do the animation is to put this code in Animate( ):

   float Time;
   #define MS_IN_THE_ANIMATION_CYCLE	10000
   . . .
   int ms = glutGet( GLUT_ELAPSED_TIME );	// milliseconds
   ms  %=  MS_IN_THE_ANIMATION_CYCLE;
   Time = (float)ms  /  (float)MS_IN_THE_ANIMATION_CYCLE;        // [ 0., 1. )
   

   where Time is a global floating-point variable and MS_IN_THE_ANIMATION_CYCLE is how many milliseconds are in the animation cycle. This sets Time to be between 0. and 1., which you can then use to set animation parameters. The advantage of this is that you will get the same number of milliseconds in the animation cycle regardless of how fast or slow a system you run this on.

7. After that works, add the Inside View by testing what view mode you are in and then using a different call to gluLookAt( ). Don't use Xrot, Yrot, and Scale if you are in the Inside Mode.

Those Vector-Manipulation Functions

The lighting of the Cessna surfaces uses two functions, Cross( ) and Unit( ). They are in your sample code already.

A Debugging Suggestion:

• One thing that has always helped Joe Graphics debug animation programs is to have a "freeze" option, toggled with the 'f' key. This freezes the animation so you can really look at your Cessna and propellers and see if they are being drawn correctly. Remember what the current freeze status is with a boolean global variable:

  
  bool	Frozen;
  

  Set Frozen to false in Reset( ). Then, freezing the animation is just a matter is setting the Idle Function to NULL. To un-freeze it, set the Idle Function back to Animate( ). So, in the Keyboard( ) callback, you could say something like:

  
  case 'f':
  case 'F':
  	Frozen = ! Frozen;
  	if( Frozen )
  		glutIdleFunc( NULL );
  	else
  		glutIdleFunc( Animate );
  	break;
  

Turn-in:

Use the Teach system to turn in:

1. Your .cpp file
2. A one-page PDF with a title, your name, your email address, a couple of nice screen shots from your program, and the link to the video demonstrating that your project does what the requirements ask for. You can use any video capture tool you want. Kaltura and Zoom work well. There are others. If you can, narrate your video so that you can tell us what it is doing. Be sure your video demonstrates all the items in the grading rubric below. If you use Kaltura, be sure your video status is changed to Unlisted so that we can get access to it to grade it.

Grading:

Feature	Points
Correctly draw the Cessna body	15
Correctly scale the propellers	15
Correctly position the propellers	15
Correctly orient the propellers	15
Correctly rotate the propellers	15
Recognizable Inside View	25
Potential Total	100

Acknowledgement:

Thanks to free3d.com for the Cessna model!