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 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any kind. ALL
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 * INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A
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package net.java.joglutils.msg.nodes;

import net.java.joglutils.msg.actions.*;
import net.java.joglutils.msg.math.*;

public class OrthographicCamera extends Camera {
  private static final float DEFAULT_HEIGHT = 2.0f;
  // Amount the most recently set height differed from the default
  private float heightScale = 1.0f;

  public Mat4f getProjectionMatrix() {
    if (projDirty) {
      projMatrix.makeIdent();
      projDirty = false;

      // Recompute matrix based on current parameters
      float zNear = getNearDistance();
      float zFar  = getFarDistance();
      float deltaZ = zFar - zNear;
      float aspect = getAspectRatio();
      float height = heightScale * DEFAULT_HEIGHT;
      float width  = height * aspect;

      if ((height == 0) || (width == 0) || (deltaZ == 0))
        return projMatrix;

      // This is a simplified version of the orthographic projection
      // matrix where it's symmetric about the origin
      projMatrix.set(0, 0,  2.0f / width);
      projMatrix.set(1, 1,  2.0f / height);
      projMatrix.set(2, 2, -2.0f / deltaZ);
      projMatrix.set(2, 3, -(zFar + zNear) / deltaZ);
    }

    return projMatrix;
  }

  /** Sets the height, in units, of the volume this orthographic
      camera views. The default height is 2.0 units. */
  public void setHeight(float height) {
    heightScale = height / DEFAULT_HEIGHT;
  }

  /** Returns the height, in units, of the volume this orthographic
      camera views. */
  public float getHeight() {
    return heightScale * DEFAULT_HEIGHT;
  }

  /** Returns the width, in units, of the volume this orthographic
      camera views, assuming the passed-in aspect ratio. */
  public float getWidth(float aspectRatio) {
    return getHeight() * aspectRatio;
  }

  /** Returns the width, in units, of the volume this orthographic
      camera views, assuming the camera's currently-set aspect
      ratio. */
  public float getWidth() {
    return getWidth(getAspectRatio());
  }

  protected Vec3f getRayStartPoint(Vec2f point, Vec3f unprojectedPoint) {
    // The easiest way to compute a reasonable ray start point is to
    // start from the unprojected 3D point and go back along the Z-axis
    Vec3f backward = Vec3f.Z_AXIS.times(getNearDistance());
    backward = getOrientation().rotateVector(backward);
    return unprojectedPoint.plus(backward);
  }

  public void render(GLRenderAction action) {
    // FIXME: unclear whether we should be doing this, or whether we
    // should have a mechanism which doesn't require mutation of the
    // camera
    setAspectRatio(action.getCurAspectRatio());
    doAction(action);
  }
}