Vectors. Vectors are used to talk about positions in 3 dimensional space, differences between one position and another, or directions.

Transcription

1 and Scripting with and Seifert Surface SLPro Conference February 25 th

2 and E.g.: 0, 0, 1, 5.3, 1.4, 22.7, x, y, z. are used to talk about positions in 3 dimensional space, differences between one position and another, or directions. There are five commonly used operations on vectors: addition (+) and subtraction ( ) scalar multiplication ( ) dot product ( ) cross product (%) Also common is to get the size, or magnitude of a vector (llvecmag in LSL).

3 and What it does: a, b, c + x, y, z = a + x, b + y, c + z a, b, c x, y, z = a x, b y, c z Examples: 1, 0, 0 + 0, 0, 1 = 1, 0, 1 What it is for: 4, 5, 6 2, 2, 2 = 2, 3, 4 Add a vector to llgetpos in llrezobject to put something near the position of the rezzer The difference between two positions gives a vector pointing from one to the other

4 and What it does: k a, b, c = k a, k b, k c Example: 4 1, 2, 3 = 4, 8, 12 What it is for: Change the size of a vector (e.g. for a mini radar) Reverse a vector by multiplying by -1

5 and What it does: a, b, c x, y, z = a x + b y + c z u v = llvecmag(u) llvecmag(v) cos(θ) where θ is the angle between the two vectors. Examples: 1, 2, 3 1, 1, 1 = = 6 u u = llvecmag(u) 2 What it is for: Find the angle between two vectors Find out which side of a plane a point is

6 and What it does: a, b, c % x, y, z = you don t really want to know u%v = llvecmag(u) llvecmag(v) sin(θ) w where θ is the angle between the two vectors and w is a vector perpendicular to both u and v. Example: 1, 0, 0 % 0, 1, 0 = 0, 0, 1 Note that unlike the other operations the order does matter: What it is for: u%v = v%u Finding a vector perpendicular to a plane Making a rotation from forward and leftward pointing vectors (coming up later)

7 and E.g.: 0, 0, 0, 1 (but you don t need to ever look at the guts of them). are used to talk about the orientation of objects, and the main use in SL is in llsetrot or llrezobject. Some methods to make : composition of

8 and Often the simplest way to get a rotation is to put the object in the orientation you want, then get it to tell you what that rotation is using: llownersay((string)()) You can then just paste whatever it tells you into your script to use that rotation.

9 and You can also use the same angles in your edit window to generate a rotation in your script with. lleuler 2Rot(DEG_TO_RAD 348, 24, 32 ) DEG_TO_RAD converts the angle from degrees to radians, which is the format the function expects. This can be a good way to generate, particularly for getting a series of orientations of an object rotating about a vertical axis for example (check out llaxisangle2rot though). is better for more complicated uses.

10 and This takes in three vectors, pointing forwards, leftwards and upwards, and returns the rotation for that orientation. The input vectors should be at right angles to each other, and length 1. Using this function, figuring out how to make a rotation is reduced to figuring out where the front, left and up of the object should point. To make a vector be length 1 use llvecnorm. If you only have two vectors, you can use cross product to get the third which will be at right angles to the first two: forward%left = up

11 and two is written: rot1 rot2. Like the cross product, the order does matter. rot1 rot2 means do rot1 first, then take that and rotate it by rot2. The main use of composition is to rotate a thing along with the bigger thing it is supposed to be attached to. This is what linked prims actually do: the orientation of a child prim is the composition of the rotation of the root prim in world, and the rotation of the child prim relative to the root prim: () = llgetlocalrot() llgetrootrotation()

12 and with vectors Composition also works on vectors: vec rot rotates the vector by rot. Again this is what linked prims actually do: the offset vector of a child prim from the root prim needs to get rotated when the root prim gets rotated: llgetpos() llgetrootposition() = llgetlocalpos() llgetrootrotation() So to rez an object with an offset vector and orientation fixed relative to the position and orientation of the rezzing object, we use llrezobject with position: llgetpos() + pos () and rotation: rot ()

13 and Thanks!