Double integral of a dot product error
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Carmine Buonagura
on 13 Oct 2020
Edited: Ameer Hamza
on 13 Oct 2020
I'm tring to solve a double integral in matlab where two dot products are evaluated, but an error arieses.
The code is:
light_dir = [-0.6626;0;-0.7490];
camera_dir = [-1;0;0];
R = sqrt(2/(4*pi));
x_c =@(theta,phi) R.*sin(theta).*cos(phi);
y_c =@(theta,phi) R.*sin(theta).*sin(phi);
z_c =@(theta) R.*cos(theta);
normal =@(theta,phi) [x_c(theta,phi); y_c(theta,phi); z_c(theta)];
fun = @(theta,phi) (dot(light_dir,normal(theta,phi))).*(dot(camera_dir,normal(theta,phi))<0).*R^2.*sin(theta);
intensity = integral2(fun,0,pi,0,2*pi);
The error is:
Error using dot (line 39)
A and B must be same size.
Error in Image_processing (line 246)
fun = @(theta,phi)
(dot(light_dir,normal(theta,phi))).*(dot(camera_dir,normal(theta,phi))<0).*R^2.*sin(theta);
Error in integral2Calc>integral2t/tensor (line 228)
Z = FUN(X,Y); NFE = NFE + 1;
Error in integral2Calc>integral2t (line 55)
[Qsub,esub] = tensor(thetaL,thetaR,phiB,phiT);
Error in integral2Calc (line 9)
[q,errbnd] = integral2t(fun,xmin,xmax,ymin,ymax,optionstruct);
Error in integral2 (line 106)
Q = integral2Calc(fun,xmin,xmax,yminfun,ymaxfun,opstruct);
Error in Image_processing (line 248)
intensity = integral2(fun,0,pi,0,2*pi);
Do you have any suggestion to let it work?
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Accepted Answer
Ameer Hamza
on 13 Oct 2020
Edited: Ameer Hamza
on 13 Oct 2020
integral2() assumes that the function handle is able to accept matrix inputs. However, the fun() function in your code does not work correctly with matrix inputs. The following codes shows a quick fix using arrayfun
light_dir = [-0.6626;0;-0.7490];
camera_dir = [-1;0;0];
R = sqrt(2/(4*pi));
x_c =@(theta,phi) R.*sin(theta).*cos(phi);
y_c =@(theta,phi) R.*sin(theta).*sin(phi);
z_c =@(theta) R.*cos(theta);
normal =@(theta,phi) [x_c(theta,phi); y_c(theta,phi); z_c(theta)];
fun = @(theta,phi) (dot(light_dir,normal(theta,phi))).*(dot(camera_dir,normal(theta,phi))<0).*R^2.*sin(theta);
intensity = integral2(@(THETA, PHI) arrayfun(@(theta,phi) fun(theta, phi), THETA, PHI) ,0,pi,0,2*pi);
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