Projection  The Slim
projection manifold provides a number of types of projections.
PlanarX, Y, & Z
The Planar projection treats the Appearance as a flat
sheet: a slide, if you will, to be projected along the X, Y, or Z axis of the
object. Another way of visualizing the effect on the object is this:
if you imagine that the shader is a sheet of paint, using this projection
is like pushing the object through the sheet. The top, bottom, and
sides get smeared, and the back face has the image reversed. Using
the planar projection on an object whose shape is decidedly not flat (a
sphere, for example) can produce unexpected (but entertaining)
effects.
PlanarZ Persp
The PlanarZ Persp projection is useful for creating nonorthographic
projections. The most typical cases are creating projections that match the cone
angles of spot lights and the field of view of cameras. You'll want to make sure
that the Field of View parameter is appropriately set for the object that
it is attached to. There's an example of using the Planar Z Persp projection in
the shader recipe the Slide Projector Light.
AutoPlanar
The Autoplanar projection treats the shader as a
flat sheet that gets pressed onto every face of a surface. Suppose
you want to apply a shader to a pyramid. Using this projection the shader
would be applied individually to each of the pyramid's faces, based on
each face's orientation. However, in exchange for the generality of
this projection you sacrifice control over individual faces.
Autoplanar projections can produce unexpected (but entertaining)
effects when used on curved surfaces.
Box
This applies a shader from six directions, as if
there were a large box around the object with a projector pointing
inward attached to each side. The difference between this and
Autoplanar is that Autoplanar applies a projection from as many
directions as there are faces, instead of just six directions.
Box Spherical
Imagine a sphere with six copies of a texture
on it, each texture occupying a sixth of the sphere. This then gets
projected onto the surface. The size of the sphere is determined by the
ProjRadius parameter. There are 12 seams where the six copies of the
texture abut each other. On spheroidal objects there will be some
distortion at the seams, but in general this is noticable mostly when
there are straight lines in the Look. This projection allows seamlessly
tiling textures to match at the seams.
Spherical
This projection applies a shader as if it were a
spherical sheet that was shrinkwrapped onto the object. It covers
objects equally from all directions. The size of the sphere is
determined by the ProjRadius parameter. There is one seam, at the back
of the sphere. While there is no distortion at the seam, there is
distortion toward the poles. Using this projection on an object whose
shape isn't really spherical can create unusual results. This
projection allows seamlessly tiling textures to match at the seams.
Cylindrical
This shrinkwraps a shader in the shape of a
cylinder onto an object. As you would expect, the sides get covered
equally, but the top and bottom get the very top of the shader smeared
across them. The cylinder is oriented so that you see the object's
front through the front of the cylinder. The cylinder's radius is
determined by the ProjRadius parameter. There is one seam, at the back
of the cylinder. Although there is no distortion at the seam, there can be
distortion elsewhere on anything but a perfect cylinder. This
projection allows seamlessly tiling textures to match at the seams.
