4
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Given a ray with a point and a vector and a plane with a point and a normal vector to the plane. You have to find the intersection point of the plane and the ray..

So your job if you choose to accept is to write a shortest function that will do the job.

RULES:
The submission must be a complete program
And that's all

INPUT FORMAT:
x y z rx ry rz //gives the ray point and the ray vectors
x y z px py pz //gives the point on the plane and the vector normal to plane

OUTPUT FORMAT:
(x,y,z) //intersection point

Test Case:
2 3 4 0.577 0.577 0.577
7 1 3 1 0 0
(7,8,9)

The shortest codes in bytes win.

References: https://www.siggraph.org/education/materials/HyperGraph/raytrace/rayplane_intersection.htm thanks orlp for the reference

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14
  • \$\begingroup\$ then i think i should remove it. \$\endgroup\$
    – Kishan Kumar
    Oct 2, 2016 at 15:20
  • \$\begingroup\$ Any specifications as to required precision? Say 3 decimal figures for example? \$\endgroup\$
    – Luis Mendo
    Oct 2, 2016 at 15:37
  • 2
    \$\begingroup\$ Some test cases would be nice. Also, relevant. \$\endgroup\$
    – orlp
    Oct 3, 2016 at 10:04
  • 1
    \$\begingroup\$ It will be very helpful if the formulae involved are included in the question, else programmers will have to search for them. \$\endgroup\$
    – rnso
    Oct 3, 2016 at 13:40
  • 2
    \$\begingroup\$ I would strongly advice to stop enforcing your very specific input/output rules. They really don't add anything to the challenge. \$\endgroup\$
    – Sanchises
    Oct 4, 2016 at 16:32

6 Answers 6

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3
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Mathematica, 20 bytes

Takes 4 lists as input. The dot product operator . has precedence over multiplication and division, so no more parentheses are needed.

#+#2(#3-#).#4/#2.#4&

Readable version:

x + v (r - x).n / v.n

where the arguments in order are x (ray point), v (ray direction), r (plane point), n (plane normal).

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3
  • \$\begingroup\$ does it give output in desired format? \$\endgroup\$
    – Kishan Kumar
    Oct 4, 2016 at 13:46
  • \$\begingroup\$ @KishanKumar If by desired format you mean with parentheses, then no. Neither is the input a bunch of numbers separated by spaces. Mathematica works in lists, which are enclosed by {} and separated by ,. \$\endgroup\$
    – user58632
    Oct 4, 2016 at 13:59
  • \$\begingroup\$ No other answer shorter than this.. So, i have accepted this answer. \$\endgroup\$
    – Kishan Kumar
    Nov 5, 2017 at 12:05
3
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Perl, 107 bytes

Tested for all test cases (i.e. not tested at all) Run with each input number on its own line on STDIN

perl -M5.010 plane.pl
0
1
0
0
0
1
3
3
1
0
0
1
^D

plane.pl:

#!/usr/bin/perl
$$_=<>for a..l;say$a+($t=($j*($g-$a)+$k*($h-$b)+$l*($i-$c))/($j*$d+$k*$e+$l*$f))*$d,$",$b+$t*$e,$",$c+$t*$f

This kind of problem is absolutely not a good match for perlgolf. Perl lacks vector operations and uses too many $s

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3
  • 3
    \$\begingroup\$ +1 for "for all test cases". \$\endgroup\$
    – Steven H.
    Oct 3, 2016 at 19:30
  • \$\begingroup\$ does it give output in desired format? \$\endgroup\$
    – Kishan Kumar
    Oct 4, 2016 at 14:09
  • \$\begingroup\$ It prints the 3 coordinates on one line separated by spaces without (). Adding the (,,) takes 10 trivial bytes (just add the extra characters to the say) \$\endgroup\$
    – Ton Hospel
    Oct 4, 2016 at 14:46
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Haskell, 137 157/102 bytes

Follows both input and output pattern. Program reads input from stdin. 157 bytes.

z=zipWith
main=do
[(p,r),(l,n)]<-map(splitAt 3.map read.words).lines<$>getContents
print$(\[a,b,c]->(a,b,c))$z(+)p$map(*(sum(z(*)n(z(-)l p))/sum(z(*)n r)))r

With an input file that has format [[x,y,z],[rx,ry,rz],[x,y,z],[px,py,pz]] and output of format [x,y,z] (102 bytes):

z=zipWith
main=do
[p,r,l,n]<-read<$>getContents
print$z(+)p$map(*(sum(z(*)n(z(-)l p))/sum(z(*)n r)))r
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5
  • \$\begingroup\$ does it follow both output and input pattern... \$\endgroup\$
    – Kishan Kumar
    Oct 4, 2016 at 14:08
  • \$\begingroup\$ The optional version did. I changed it to do it anyway, at the cost of 20 bytes. \$\endgroup\$
    – Angs
    Oct 4, 2016 at 16:15
  • \$\begingroup\$ well, remove the extra 20 bytes. no need to comply with my input pattern \$\endgroup\$
    – Kishan Kumar
    Oct 4, 2016 at 17:36
  • \$\begingroup\$ It always complied with the input pattern - the output had different parentheses. I'll add an option that follows neither format. \$\endgroup\$
    – Angs
    Oct 4, 2016 at 20:26
  • \$\begingroup\$ Do the one that saves you most bytes.. \$\endgroup\$
    – Kishan Kumar
    Oct 5, 2016 at 3:19
1
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R, 88 bytes

x=scan()
v=scan()
r=scan()
n=scan()
C=cat
C("(");C(x+v*sum((r-x)*n)/sum(v*n),sep=", ");C(")")

Adapted from the Mathematica answer. Takes the following values from stdin, x (ray point), v (ray direction), r (plane point), n (plane normal). Outputs (7, 8, 9) for the test case.

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0
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JavaScript (ES6), 157 bytes

This could probably be shorter. The test case is subject to rounding errors, but otherwise it respects the challenge.

P=prompt;[a,b,c,d,e,f,g,h,i,j,k,l]=(P()+' '+P()).split` `.map(e=>+e);alert('('+(a+(t=(j*(g-a)+k*(h-b)+l*(i-c))/(j*d+k*e+l*f))*d)+','+(b+t*e)+','+(c+t*f)+')')
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0
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JavaScript (ES6), 93 bytes

(a,b,c,A,B,C,x,y,z,X,Y,Z)=>`(${t=X*(x-a)+Y*(y-b)+Z*(z-c)/(X*A+Y*B+Z*C),[a+t*A,b+t*B,c+t*C]})`


f=
(a,b,c,A,B,C,x,y,z,X,Y,Z)=>`(${t=X*(x-a)+Y*(y-b)+Z*(z-c)/(X*A+Y*B+Z*C),[a+t*A,b+t*B,c+t*C]})`

console.log(f(2, 3, 4, 0.577350269, 0.577350269, 0.577350269, 7, 1, 3, 1, 0, 0))

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