// Example.java
// Sean Cier, 29 July 1997
// Port of main.c, place8_2.c, and frame8_4.c from the PRMan tutorial
//   (The latter two are listings 8.2 and 8.4, respectively, from
//    The RenderMan Companion)

import com.PostHorizon.renderMan.*;
import com.PostHorizon.renderMan.rib.*;
import java.util.Hashtable;

public abstract class Example {
  protected abstract void   go()
    throws RMException;
  protected abstract String getFilename();
  protected abstract int    getXRes();
  protected abstract int    getYRes();
  protected abstract double getCamZoom();
  protected abstract double getCamRoll();
  protected abstract Point  getCameraFrom();
  protected abstract Point  getCameraTo();

  public RenderMan renderer;


  public Example() {
    renderer = new RIBOutASCII(System.out, true, 2);
    ((RIBOut)renderer).setStrictParamTyping(true);
  }

  protected void execute()
    throws RMException {
    Point cameraTo, cameraFrom, cameraDir;

    renderer.begin();

      renderer.display(getFilename(), RenderMan.FILE, RenderMan.RGBA, null);
      renderer.format(getXRes(), getYRes(), -1.0);
      renderer.shadingRate(1.0);
      renderer.cropWindow(0.0, 1.0, 0.0, 1.0);

      frameCamera(getXRes()*getCamZoom(), getXRes(), getYRes());

      cameraTo = getCameraTo();
      cameraFrom = getCameraFrom();
      cameraDir = new Point(cameraTo.getX() - cameraFrom.getX(),
		            cameraTo.getY() - cameraFrom.getY(),
		            cameraTo.getZ() - cameraFrom.getZ());
      placeCamera(cameraFrom, cameraDir, getCamRoll());

      renderer.worldBegin();
        go();
      renderer.worldEnd();

    renderer.end();
    }


  protected void frameCamera(double focalLength,
			     double frameWidth, double frameHeight)
    throws RMException {
    double fov;
    Hashtable params = new Hashtable();

    if (focalLength != 0.0) {
      fov = 2 * Math.atan((Math.min(frameWidth, frameHeight) * 0.5) /
			  focalLength) *
	    180.0/Math.PI;
      params.put(RenderMan.FOV, new Double(fov));
      renderer.projection(RenderMan.PERSPECTIVE, params);
      params.clear();
    } else
      renderer.projection(RenderMan.ORTHOGRAPHIC, null);
    renderer.frameAspectRatio(frameWidth/frameHeight);
  }

  protected void placeCamera(Point position, Point direction, double roll)
    throws RMException {
    renderer.identity();
    renderer.rotate(-roll, 0.0, 0.0, 1.0);
    aimZ(direction);
    renderer.translate(-position.getX(), -position.getY(), -position.getZ());
  }

  protected void aimZ(Point direction)
    throws RMException {
      double xzlen, yzlen, yrot, xrot;

      if ((direction.getX() == 0) &&
	  (direction.getY() == 0) &&
	  (direction.getZ() == 0))
	return;

      xzlen = Math.sqrt(direction.getX()*direction.getX() +
			direction.getZ()*direction.getZ());
      if (xzlen == 0)
	yrot = (direction.getY() < 0) ? 180 : 0;
      else
	yrot = 180*Math.acos(direction.getZ() / xzlen) / Math.PI;

      yzlen = Math.sqrt(direction.getY()*direction.getY() +
			xzlen*xzlen);
      xrot = 180*Math.acos(xzlen/yzlen)/Math.PI;


      if (direction.getY() > 0)
	renderer.rotate( xrot, 1.0, 0.0, 0.0);
      else
	renderer.rotate(-xrot, 1.0, 0.0, 0.0);
      if (direction.getX() > 0)
	renderer.rotate(-yrot, 0.0, 1.0, 0.0);
      else
	renderer.rotate( yrot, 0.0, 1.0, 0.0);
    }
}