# roty

## rotation around y axis

Like all linear transformations that command is in 2 modes: direct and matrix.

## roty obj

### roty(an)obj(id)

Rotates the object id angle an around y ayis versus its center of gravity.

### roty(an) vertex(s) obj(id)

Rotates vertices s of the object id angle an around y axis versus its center of gravity.

### roty(an) poi(x,y,z) obj(id)

Rotates the object id angle an around tth y axis versus point (x,y,z).
Note:
objt is fog, light, var, vol, view.
Exeamples:
`roty(PI/2) poi(100,-20,50) vertex[1,5] vol(1,3);` y rotates vertices (1,2,3,4,5) of volumes 1 et 3 angle PI/2around point (100,-20,50).
`roty(PI/2) var("x");` y rotates variable x angle PI/2 around its center of gravity.
`roty(.1*PI) eye view(1);` angle .1*PI around y axis the eys of the view 1.

### roty(a1,a2)vol(a)roty(b1,b2)vol(b)

Varies roty matrix vol(a) in the interval [a1,a2] when roty matrix vol(b) varies in the interval [b1,b2].
May be used to attach roty variations of volume a to those of its father b.
Note: roty(b1,b2) can be any other transformation transf(b1,b2).

## roty image

### roty(an) image(id)

Makes identic first ligne and last ligne of the image id.
Notes:
1) an is ethe portion of the image (between 0 and PI) affected by this operation.
2) Blur appears in this portion.
3) Useful for mapping an image on a closed surface in y.
4) If identifier id is absent, the current image by default.
Example:
`roty(.1*PI) image(1);` makes periodic the image by changing one tenth of its surface.

## rotx matrix

### roty matrix vol(id)

Returns the angle of rotation about y of the matrix of the volume id.
Options:
format(f): modulo f.

### roty(a)matrix vol(id)

Rotates angle a around y the volume id by changing its matrix.
Options:
ini: the transformation is the basic.

## roty view

### roty(an)eye view(id)

Rotates the eye of the view id angle an around y axis.

### roty(an)aim view(id)

Rotates the aim point of the view id angle an around y axis.
Options:
validate(0): rotationfrom the initial position.