Skip to content

Instantly share code, notes, and snippets.

Embed
What would you like to do?
function camera_matrix = lookAt(eyePos, target, up)
% lookAt function for right-handed coordinate system
% Returns the 4x4 camera matrix that maps homogeneous 3D world coordinates
% (xW, yW, zW, W) to homogeneous 2D view coordinates (xV, yV, V)
zaxis = eyePos - target; % The "forward" vector.
zaxis = zaxis / norm(zaxis);
xaxis = cross(up, zaxis); % The "right" vector.
xaxis = xaxis / norm(xaxis);
yaxis = cross(zaxis, xaxis); % The "up" vector.
orientation = [xaxis(1), yaxis(1), zaxis(1), 0;
xaxis(2), yaxis(2), zaxis(2), 0;
xaxis(3), yaxis(3), zaxis(3), 0;
0, 0, 0, 1];
translation = eye(4);
translation(4,1:3) = -eyePos;
camera_matrix = translation * orientation;
end
% eye = [...];
target = [0 0 0];
up = [0 0 1];
%
% generate some dummy data
%
figure(1);
clf;
subplot(1, 2, 1);
scatter3(0,0,0,'x');
hold on;
n_pts = 100;
points = zeros(3, n_pts);
for i = 1:n_pts
points(:, i) = [cos(i/n_pts*2*pi), .25 * rand(), sin(i/n_pts*2*pi)];
scatter3(points(1, i), points(2, i), points(3, i));
end
xlabel('X');
ylabel('Y');
zlabel('Z');
daspect([1 1 1]);
xlim([-4, 4]);
ylim([-4, 4]);
%
% animate the camera
%
n_camera_pos = 32;
filename1 = 'camera_anim.gif';
clear imind
for i = 1:n_camera_pos
eye = [4 * sin((i-1)/n_camera_pos*2*pi), 3 * cos((i-1)/n_camera_pos*2*pi), 1];
subplot(1, 2, 1);
scatter3(eye(1), eye(2), eye(3), '+');
hold on
camera_matrix = lookAt(eye, target, up);
camera_matrix = camera_matrix(:,1:3);
subplot(1, 2, 2);
cla
for j = 1:n_pts
p = camera_matrix' * [points(1, j) points(2, j) points(3, j) 1]';
hold on
scatter(p(1) / p(3), p(2) / p(3));
end
daspect([1 1 1]);
xlim([-1 1])
ylim([-1 1])
drawnow
frame = getframe(1);
im = frame2im(frame);
[im, cm] = rgb2ind(im, 256);
if i == 1
imwrite(im, cm, filename, 'gif', 'writemode', 'overwrite', 'LoopCount', inf, 'DelayTime', .1);
else
imwrite(im, cm, filename, 'gif', 'writemode','append', 'DelayTime', .1);
end
% pause(.1);
end
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
You can’t perform that action at this time.