Expression 33: left parenthesis, sin left parenthesis, "r" Subscript, "x" "y" , Baseline , right parenthesis "c" Subscript, "x" , Baseline , sin left parenthesis, "r" Subscript, "x" "z" , Baseline , right parenthesis cos left parenthesis, "r" Subscript, "x" "y" , Baseline , right parenthesis "c" Subscript, "y" , Baseline , right parenthesissinrxycx,sinrxzcosrxycy
00
domain t Minimum:
less than or equal to "t" less than or equal to≤t≤
11
domain t Maximum:
33
what the heck? this is not even close!
34
or so it looks. check again and you'll notice the bounds of the circle are the same as the bounds of the x axis. but why isn't it exactly equal? aren't we following the x axis?
35
well, it is true that we're following the x axis, but we have to remember we are also following the y axis. this circle is defined on the xy plane, which means we have to find the coefficients of y as well.
36
before i show you, try for a bit to see if you can get them yourself!
37
Expression 38:
38
Expression 39:
39
Expression 40:
40
Expression 41:
41
Expression 42:
42
Expression 43:
43
Expression 44:
44
Expression 45:
45
if you tried, that's cool, if you didn't, that's a little less cool but still acceptable. we're still learning!
46
Expression 47: left parenthesis, cos left parenthesis, "r" Subscript, "x" "y" , Baseline , right parenthesis "c" Subscript, "x" , Baseline , negative sin left parenthesis, "r" Subscript, "x" "y" , Baseline , right parenthesis sin left parenthesis, "r" Subscript, "x" "z" , Baseline , right parenthesis "c" Subscript, "y" , Baseline , right parenthesiscosrxycx,−sinrxysinrxzcy
00
domain t Minimum:
less than or equal to "t" less than or equal to≤t≤
11
domain t Maximum:
47
these are the coefficients. but what do we do now? we have them both separate, but we want one that covers the plane, and is actually 3 dimensional looking.
48
luckily, this part is a lot easier than it seems. all we need to do is put the products together. remember that we've been multiplying these coefficients by either cos(2pi*t) or sin(2pi*t). this has to come with the coefficients.
49
Expression 50: left parenthesis, sin left parenthesis, "r" Subscript, "x" "y" , Baseline , right parenthesis "c" Subscript, "x" , Baseline plus cos left parenthesis, "r" Subscript, "x" "y" , Baseline , right parenthesis "c" Subscript, "y" , Baseline , sin left parenthesis, "r" Subscript, "x" "z" , Baseline , right parenthesis cos left parenthesis, "r" Subscript, "x" "y" , Baseline , right parenthesis "c" Subscript, "x" , Baseline minus sin left parenthesis, "r" Subscript, "x" "y" , Baseline , right parenthesis sin left parenthesis, "r" Subscript, "x" "z" , Baseline , right parenthesis "c" Subscript, "y" , Baseline , right parenthesissinrxycx+cosrxycy,sinrxzcosrxycx−sinrxysinrxzcy
00
domain t Minimum:
less than or equal to "t" less than or equal to≤t≤
11
domain t Maximum:
50
now we know how to project any point on the (x,y) plane! if we wanted to project (0.3,0.2), we would just replace our c_x and c_y values.
51
Hidden Label: left parenthesis, sin left parenthesis, "r" Subscript, "x" "y" , Baseline , right parenthesis .3 plus cos left parenthesis, "r" Subscript, "x" "y" , Baseline , right parenthesis .2 , sin left parenthesis, "r" Subscript, "x" "z" , Baseline , right parenthesis cos left parenthesis, "r" Subscript, "x" "y" , Baseline , right parenthesis .3 minus sin left parenthesis, "r" Subscript, "x" "y" , Baseline , right parenthesis sin left parenthesis, "r" Subscript, "x" "z" , Baseline , right parenthesis .2 , right parenthesissinrxy.3+cosrxy.2,sinrxzcosrxy.3−sinrxysinrxz.2
Label
52
but what about 3d? what about the z axis?
53
you're in luck! this part is actually easier than the (x,y) plane.
54
Hidden Label: left parenthesis, 0 , "z" Subscript, "y" , Baseline , right parenthesis0,zy
Label
55
notice what happens to this point as we drag our xy rotation.
56
absolutely nothing! it stays fixed at zero, so we already have our first coefficient, zero.
57
but what about the y value? well, it's only dependent on the xz rotation, and when that is zero, the point is at one. you know what that means!
58
Expression 59: left parenthesis, 0 , cos left parenthesis, "r" Subscript, "x" "z" , Baseline , right parenthesis "c" Subscript, "y" , Baseline , right parenthesis0,cosrxzcy
00
domain t Minimum:
less than or equal to "t" less than or equal to≤t≤
11
domain t Maximum:
59
our last coefficient is cos(r_xz). now we can write a formula for projection!
60
Expression 61: "P" left parenthesis, "x" , "y" , "z" , right parenthesis equals left parenthesis, sin left parenthesis, "r" Subscript, "x" "y" , Baseline , right parenthesis "x" plus cos left parenthesis, "r" Subscript, "x" "y" , Baseline , right parenthesis "y" , cos left parenthesis, "r" Subscript, "x" "y" , Baseline , right parenthesis sin left parenthesis, "r" Subscript, "x" "z" , Baseline , right parenthesis "x" minus sin left parenthesis, "r" Subscript, "x" "y" , Baseline , right parenthesis sin left parenthesis, "r" Subscript, "x" "z" , Baseline , right parenthesis "y" plus cos left parenthesis, "r" Subscript, "x" "z" , Baseline , right parenthesis "z" , right parenthesisPx,y,z=sinrxyx+cosrxyy,cosrxysinrxzx−sinrxysinrxzy+cosrxzz
61
don't worry if this looks complicated! it's just everything we've done compressed into one line that you can input coordinates into.
62
Hidden Label: "P" left parenthesis, 0.2 , 0.1 , 0.6 , right parenthesisP0.2,0.1,0.6
Label
63
what about functions though? well, that's the next section!