rgl (version 0.111.6)

shadow3d: Project shadows of mesh onto object.

Description

Project a mesh onto a surface in a scene so that it appears to cast a shadow onto the surface.

Usage

shadow3d(obj, mesh, plot = TRUE, up = c(0, 0, 1),
         P = projectDown(up), outside = FALSE,
         ...)

Value

The returned value from filledContour3d.

Arguments

obj

The target object which will show the shadow.

mesh

The mesh which will cast the shadow.

plot

Whether to plot the result.

up

Which direction is “up”?

P

The projection to use for draping, a 4x4 matrix. See drape3d for details on how P is used.

outside

Should the function compute and (possibly) plot the region outside of the shadow?

...

Other arguments to pass to filledContour3d, which will do the boundary calculations and plotting.

Author

Duncan Murdoch

Details

shadow3d internally constructs a function that is zero on the boundary of the shadow and positive inside, then draws filled contours of that function. Because the function is nonlinear, the boundaries will be approximate, with the best approximation resulting from a large value of filledContour3d parameter minVertices.

If outside = TRUE, the first color used by filledContour3d will indicate the inside of the shadow, and the second color will indicate the exterior.

See Also

drape3d, facing3d

Examples

open3d()
obj <- translate3d(scale3d(oh3d(), 0.3, 0.3, 0.3), 0,0,2)
shade3d(obj, col = "red")
target <- icosahedron3d()

# We offset the target using polygon_offset = 1 so that the
# shadow on its surface will appear clearly.

shade3d(target, col = "white", polygon_offset = 1)

# minVertices = 1000 leaves noticeable artifacts on the edges
# of the shadow.  A larger value gives a better result, but is
# slower.

# We use facing3d(target) so the shadow and outside part only 
# appear on the upper side of the target

shadow3d(facing3d(target), obj, minVertices = 1000, plot=TRUE,
         col = c("yellow", "blue"), outside = TRUE)