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BoofCV is an open source Java library for real-time computer vision and robotics applications.
There is a newer version: 1.1.7
/*
 * Copyright (c) 2021, Peter Abeles. All Rights Reserved.
 *
 * This file is part of BoofCV (http://boofcv.org).
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package boofcv.alg.geo.bundle;

import boofcv.abst.geo.bundle.BundleAdjustmentSchur;
import boofcv.abst.geo.bundle.SceneObservations;
import boofcv.abst.geo.bundle.SceneStructureCommon;
import boofcv.abst.geo.bundle.SceneStructureProjective;
import boofcv.alg.geo.PerspectiveOps;
import boofcv.struct.geo.PointIndex2D_F64;
import georegression.struct.point.Point2D_F64;
import georegression.struct.point.Point3D_F64;
import georegression.struct.point.Point4D_F64;

/**
 * 
 * Computes observations errors/residuals for projective bundle adjustment as implemented using
 * {@link org.ddogleg.optimization.UnconstrainedLeastSquares}. Parameterization is done using
 * the format in {@link CodecSceneStructureProjective}.
 * 
 *
 * 
 * cost(P) = (1/(m*n))*∑_i ∑_j ||x_j - (1/z)*P_i*X_j||²
 * 
 *
 * @author Peter Abeles
 * @see SceneStructureProjective
 * @see SceneObservations
 */
@SuppressWarnings({"NullAway.Init"})
public class BundleAdjustmentProjectiveResidualFunction
		implements BundleAdjustmentSchur.FunctionResiduals {
	private SceneStructureProjective structure;
	private SceneObservations observations;

	// number of parameters being optimised
	private int numParameters;
	// number of observations. 2 for each point in each view
	private int numObservations;

	// Storage for rendered output
	private final Point2D_F64 predictedPixel = new Point2D_F64();
	private final PointIndex2D_F64 observedPixel = new PointIndex2D_F64();

	// Used to write the "unknown" paramters into the scene
	private final CodecSceneStructureProjective codec = new CodecSceneStructureProjective();

	// Point in world frame
	private final Point3D_F64 p3 = new Point3D_F64();
	private final Point4D_F64 p4 = new Point4D_F64();

	// Pixel in homogenous image coordinate
	private final Point3D_F64 pix = new Point3D_F64();

	/**
	 * Specifies the scenes structure and observed feature locations
	 */
	@Override
	public void configure( SceneStructureProjective structure,
						   SceneObservations observations ) {
		this.structure = structure;
		this.observations = observations;

		numObservations = observations.getObservationCount();
		numParameters = structure.getParameterCount();
	}

	@Override
	public int getNumOfInputsN() {
		return numParameters;
	}

	@Override
	public int getNumOfOutputsM() {
		return numObservations*2;
	}

	@Override
	public void process( double[] input, double[] output ) {

		// write the current parameters into the scene's structure
		codec.decode(input, structure);

		if (structure.isHomogenous())
			project4(output);
		else
			project3(output);
	}

	/**
	 * projection from 3D coordinates
	 */
	private void project3( double[] output ) {
		int observationIndex = 0;
		for (int viewIndex = 0; viewIndex < structure.views.size; viewIndex++) {
			SceneStructureProjective.View view = structure.views.data[viewIndex];
			SceneObservations.View obsView = observations.views.data[viewIndex];
			SceneStructureCommon.Camera camera = structure.cameras.get(view.camera);

			for (int i = 0; i < obsView.size(); i++) {
				obsView.getPixel(i, observedPixel);
				SceneStructureCommon.Point worldPt = structure.points.data[observedPixel.index];
				worldPt.get(p3);

				// Apply projective camera to point in world coordinates
				PerspectiveOps.renderPixel(view.worldToView, p3, pix);

				// Apply camera model to pixel in homogenous coordinates
				camera.model.project(pix.x, pix.y, pix.z, predictedPixel);

				// Save results
				int outputIndex = observationIndex*2;
				output[outputIndex] = predictedPixel.x - observedPixel.p.x;
				output[outputIndex + 1] = predictedPixel.y - observedPixel.p.y;
				observationIndex++;
			}
		}
	}

	/**
	 * projection from homogenous coordinates
	 */
	private void project4( double[] output ) {
		int observationIndex = 0;
		for (int viewIndex = 0; viewIndex < structure.views.size; viewIndex++) {
			SceneStructureProjective.View view = structure.views.data[viewIndex];
			SceneObservations.View obsView = observations.views.data[viewIndex];
			SceneStructureCommon.Camera camera = structure.cameras.get(view.camera);

			for (int i = 0; i < obsView.size(); i++) {
				obsView.getPixel(i, observedPixel);
				SceneStructureCommon.Point worldPt = structure.points.data[observedPixel.index];
				worldPt.get(p4);

				// Apply projective camera to point in world coordinates
				PerspectiveOps.renderPixel(view.worldToView, p4, pix);

				// Apply camera model to pixel in homogenous coordinates
				camera.model.project(pix.x, pix.y, pix.z, predictedPixel);

				// Save results
				int outputIndex = observationIndex*2;
				output[outputIndex] = predictedPixel.x - observedPixel.p.x;
				output[outputIndex + 1] = predictedPixel.y - observedPixel.p.y;
				observationIndex++;
			}
		}
	}
}