/* Puts up a fence around the barn.  Demonstrates display lists and affine
   transforms.

   This program uses twGround and twSky to draw those objects.  The sky
   has the fun property of being opaque only on the inside, so you can
   look through it into the scene, but you see it behind your objects.
   This is accomplished by using one-sided polygons (which is not the TW
   default).

   The coordinate system for this scene has y=0 as the ground, and the
   origin approximately in the center of the front edge, but see the
   bounding box for details.

Written by Caroline Geiersbach and Scott D. Anderson
scott.anderson@acm.org
Summer 2003

Modified in Fall 2006 to put a picket on the ground.  This clarifies the
difference between the display list (which makes drawing a picket easier)
and the use of multiple affine transformations without push/pop of the
modelview matrix.

*/

#include <stdio.h>
#include <math.h>
#include <tw.h>

/* A picket is, essentially, a barn with two horizontal rails.  The rails
   are 2D quads, and this vertex array gives the vertices for the lower rail. */

twTriple rail [] =
{
  {0,0,0},
  {5,0,0},
  {5,2,0},
  {0,2,0}
};

void drawRail () {
    glBegin(GL_QUADS);
    {
        glVertex3fv(rail[0]);
        glVertex3fv(rail[1]);
        glVertex3fv(rail[2]);
        glVertex3fv(rail[3]);
    }
    glEnd();
}

/* Draws one picket.  The picket is 5 wide, 10 high, and 2 deep, with the
   reference point at the lower left front of the picket. Rails stick out
   0.5 to the left and are flat planes through the middle of the picket,
   with a width of 5 and a height of 2, with the bottom edge at heights 1
   and 4. */

void drawPicket() {
  twTriple maroon = {0.5,0,0};
  twTriple black  = {0,0,0};
  twTriple orange = {1,0.5,0};

  glPushMatrix();
  glScalef(4,10,2); // must scale to create 4*10*2 barn
  twSolidBarn(maroon, black, orange);
  glPopMatrix();
  glPushMatrix();
  twColorName(TW_OLIVE);
  glTranslatef(-0.5,1,-1);
  drawRail();
  glTranslatef(0,3,0);
  drawRail();
  glPopMatrix();
}    

// The following is an arbitrary numeric identifier for this display list.
// Here, we use 100 just because it is clearly not a coordinate of a
// vertex, a scale factor, or any other number in the program. */

const int PICKET = 100;

void drawInit() {
  /* Create a call list for one picket of the fence.  The first argument
     is our numeric constant.  The second requests that the graphics
     pipeline just record this display list, but don't draw anything. */
  glNewList(PICKET, GL_COMPILE);
  drawPicket();
  glEndList();
}

void display(void) {
    twDisplayInit();
    twCamera();

    // draw ground
    twColorName(TW_GREEN);
    twGround();

    // draw sky
    twTriple lightSkyBlue = { 135.0/255.0, 206.0/255.0, 250.0/255.0 };
    twColor(lightSkyBlue,0,0);
    twSky();

    // draw a picket lying on the ground in the middle of the field.  With
    // the exception of using CallList instead of something like
    // drawPicket(), this is the same an any drawing code.
    glPushMatrix();
    glTranslatef(0,0,-40);
    glRotatef(30,0,1,0);
    glRotatef(-90,1,0,0);
    glTranslatef(0,0,2);
    glCallList(PICKET);
    glPopMatrix();

    // draw front fence
    glPushMatrix();
    glTranslatef(-40,0,0);
    for(int i=0;i<20;i++) {
        glCallList(PICKET);
        glTranslatef(5,0,0);
    }
    glPopMatrix();
  
    // draw right side fence
    glPushMatrix();
    glTranslatef(60,0,0);
    glRotatef(90,0,1,0); 
    for(int i=0;i<25;i++) {
        glCallList(PICKET);
        glTranslatef(5,0,0);
    }
    glPopMatrix();
  
    // draw left side fence
    glPushMatrix();
    glTranslatef(-40,0,0);
    glRotatef(90,0,1,0);
    for(int i=0;i<17;i++) {
        glCallList(PICKET);
        glTranslatef(5,0,0);
    }
    glPopMatrix();

    // draw barn
    glPushMatrix();
    glTranslatef(-40,0,-125);
    glRotatef(-90,0,1,0);
    glScalef(40,35,50);
    twTriple teal = {0,0.5,0.5};
    twTriple dark_blue = {0,0,0.5};
    twTriple cyan = {0,1,1};
    twSolidBarn(teal,dark_blue,cyan);
    glPopMatrix();

    glFlush();
    glutSwapBuffers();       // necessary for animation
}

int main(int argc, char** argv) {
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
  twInitWindowSize(500,500);
  glutCreateWindow(argv[0]);
  drawInit();
  glutDisplayFunc(display);
  // the real limits are is -40,60 and -125,5
  twBoundingBox(-45,65,0,65,-130,5);
  glLineWidth(2);
  twMainInit(); 
  glutMainLoop();
  return 0;
}