Help for a "Surface and Flux integrals" program

11042017, 10:40 AM
Post: #16




RE: Help for a "Surface and Flux integrals" program
(11042017 10:08 AM)salvomic Wrote: Also we could return a list with the I1,I2,I3 values (items of column vector of N(P), normal vector of the surface)... Not sure what you expect from that but keep in mind that while I is a normal vector in the sense that it is orthogonal to the surface, it is not normalised to length 1 (unlike n). The relation between the differentials is \[\mathbf{I} du dv = \mathbf{n} dS \] and in this expression only n is normalised. This means that the length of I depends on the chosen parametrisation in terms of (u, v), e.g. you can scale (u,v) up or down and I will change accordingly. In short: if you want to return a normal vector that is also normalised (length 1) then you must divide I by its l2 norm. 

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