plotCamera

Plot a camera in 3-D coordinates

Syntax

cam = plotCamera

cam = plotCamera(cameraTable)

cam = plotCamera(Name,Value)

Description

cam = plotCamera plots a default camera in 3-D coordinates in the current axes. The function returns cam, a Camera object that contains the properties of the plotted camera.

cam = plotCamera(cameraTable) plots one or more cameras specified by cameraTable.

cam = plotCamera(Name,Value) specifies options using one or more name-value pair arguments. For example, 'Opacity',0.4 sets the opacity of the plotted camera to 0.4.

The name-value pair arguments set the associated properties of the plotted camera visualization object.

Examples

Plot Animated Camera Using Absolute Pose

Create a rigid3d object.

R = [1 0 0; 0 0 -1;0 1 0];
t = [10 0 20];
pose = rigid3d(R,t);

Plot a camera with an opacity of zero and an absolute pose based on the created rigid3d object.

cam = plotCamera('AbsolutePose',pose,'Opacity',0)

cam = 
  Camera with properties:

           Parent: [1x1 Axes]
             Size: 1
     AbsolutePose: [1x1 rigid3d]
          Visible: 1
      AxesVisible: 0
    ButtonDownFcn: ''
            Color: [1 0 0]
          Opacity: 0
            Label: ''

Set viewing properties for the current axes.

grid on
axis equal
axis manual

Expand the viewable limits of each axis. These changes enable the entire animation to be visible in the next step.

xlim([-15 20]);
ylim([-15 20]);
zlim([15 25]);

Rotate the camera around the y-axis.

for theta = 0:pi/64:10*pi
    T = [cos(theta) 0 sin(theta);0 1 0;-sin(theta) 0 cos(theta)];
    cam.AbsolutePose = rigid3d(T * R, [10 * cos(theta), 10 * sin(theta), 20]);
    drawnow();
end

Visualize Camera Extrinsics

Create a set of calibration images.

images = imageSet(fullfile(toolboxdir('vision'),'visiondata','calibration','slr'));

Detect the checkerboard corners in the images.

[imagePoints,boardSize] = detectCheckerboardPoints(images.ImageLocation);

Generate the world coordinates of the checkerboard corners in the pattern-centric coordinate system, with the upper-left corner at (0,0). Set the square size to 29 mm.

squareSize = 29;
worldPoints = generateCheckerboardPoints(boardSize,squareSize);

Calibrate the camera.

cameraParams = estimateCameraParameters(imagePoints,worldPoints);

Load an image at its new location.

imOrig = imread(fullfile(toolboxdir('vision'),'visiondata','calibration','slr','image9.jpg'));
figure; imshow(imOrig,'InitialMagnification',50);
title('Input Image');

Undistort the image.

im = undistortImage(imOrig,cameraParams);

Find the reference object in the new image.

[imagePoints,boardSize] = detectCheckerboardPoints(im);

Compute the new extrinsics.

[rotationMatrix,translationVector] = extrinsics(imagePoints,worldPoints,cameraParams);

Plot the world points.

figure;
plot3(worldPoints(:,1),worldPoints(:,2),zeros(size(worldPoints, 1),1),'*');
hold on

Mark the origin.

plot3(0,0,0,'g*');

Compute the camera location and orientation.

orientation = rotationMatrix';
location = -translationVector * orientation;

Plot the camera.

absPose = rigid3d(orientation,location);
cam = plotCamera('AbsolutePose',absPose,'Size',20);

Make the z -axis point down.

set(gca,'CameraUpVector',[0 0 -1]);

Set the view parameters.

camorbit(gca,-110,60,'data',[0 0 1]);
axis equal
grid on

Turn on 3-D rotation.

cameratoolbar('SetMode','orbit');

Label the axes.

xlabel('X (mm)');
ylabel('Y (mm)');
zlabel('Z (mm)');

Input Arguments

cameraTable — Properties of cameras for visualization

table

Properties of cameras for visualization, specified as a table. Each row represents a single camera. Each column title must match the name-part of a name-value pair argument. The nth-row values set the properties for the nth element of cam. You cannot specify values for 'Parent'. If the table contains a 'ViewId' column, then the view IDs are used to set the 'Label' values of the cameras.

Name-Value Arguments

Specify optional comma-separated pairs of Name,Value arguments. Name is the argument name and Value is the corresponding value. Name must appear inside quotes. You can specify several name and value pair arguments in any order as Name1,Value1,...,NameN,ValueN.

Example: 'Size',0.3 specifies the camera-base width as 0.3.

AbsolutePose — Camera absolute pose

rigid3d object

Camera absolute pose in the world coordinate system, specified as the comma-separated pair consisting of 'AbsolutePose' a rigid3d object.

Size — Camera-base width

1 (default) | positive real number

Camera-base width, specified as the comma-separated pair consisting of 'Size' and a positive real number.

Label — Camera label

'' (default) | character vector | string scalar

Camera label, specified as the comma-separated pair consisting of 'Label' and a character vector or a string scalar.

Color — Camera color

[1 0 0] (red) (default) | RGB triplet

Camera color, specified as the comma-separated pair consisting of 'Color' and an RGB triplet. An RGB triplet is a three-element row vector whose elements specify the intensities of the red, green, and blue components of the color. The intensities must be in the range [0, 1].

Opacity — Camera opacity

0.2 (default) | scalar in the range [0,1]

Camera opacity, specified as the comma-separated pair consisting of 'Opacity' and a scalar in the range [0,1].

Visible — Camera visibility

true or 1 (default) | false or 0

Camera visibility, specified as the comma-separated pair consisting of 'Visible' and a numeric or logical 1 (true) or 0 (false).

AxesVisible — Camera axes visibility

false or 0 (default) | true or 1

Camera axes visibility, specified as the comma-separated pair consisting of 'AxesVisible' and a numeric or logical 1 (true) or 0 (false).

ButtonDownFcn — Callback function

'' (default) | function handle

Callback function, specified as the comma-separated pair consisting of 'ButtonDownFcn' and a function handle that executes when you click the camera.

Parent — Output axes

axes handle

Output axes, specified as the comma-separated pair consisting of 'Parent' and an axes handle. By default, plotCamera uses the current axes handle. To return the current axes, use the gca function.

Output Arguments

cam — Camera visualization object

Camera object | row vector of Camera objects

Camera visualization object, returned as one of these options.

• Camera object — The function returns this option when plotting a single camera. Name-value pair arguments or cameraTable input elements set the corresponding Camera object properties.

• Row vector of Camera objects — The function returns this option when plotting multiple cameras. The nth -row values of the cameraTable input set the properties for the nth Camera object in this vector.

Camera objects are created using the vision.graphics.Camera class.