\name{feDiffuseLighting}
\alias{feDiffuseLighting}
\title{
  Light an image using the alpha channel as a bump map.
}
\description{
  This filter primitive lights an image using the alpha channel as a
  bump map. The resulting image is an RGBA opaque image based on the
  light colour with \code{alpha = 1} everywhere. The lighting
  calculation follows the standard diffuse component of the Phong
  lighting model. The resulting image depends on the light colour, light
  position and surface geometry of the input bump map.
}
\usage{
feDiffuseLighting(input = NA,
                  surfaceScale = 1, diffuseConstant = 1,
                  kernelUnitLength = NA, col = "white",
                  lightSource = NULL, ...)
}
\arguments{
  \item{input}{
    Identifies an input for this filter primtive. See
    \code{\link{filterInputs}}.
  }
  \item{surfaceScale}{
    Scale applied to the input alpha surface.
  }
  \item{diffuseConstant}{
    \code{kd} in the Phong lighting model. Must be non-negative.
  }
  \item{kernelUnitLength}{
    The first number is the \code{dx} value. The second number is the
    \code{dy} value. If the \code{dy} value is not specified, it
    defaults to the same value as \code{dx}. Indicates the intended
    distance in current filter units (i.e., units as determined by the
    value of parent filter container's \code{primitiveUnits}) for
    \code{dx} and \code{dy}, respectively, in the surface normal
    calculation formulas. By specifying value(s) for
    \code{kernelUnitLength}, the kernel becomes defined in a scalable,
    abstract coordinate system. If \code{kernelUnitLength} is not
    specified, the \code{dx} and \code{dy} values should represent very
    small deltas relative to a given (x,y) position, which might be
    implemented in some cases as one pixel in the intermediate image
    offscreen bitmap, which is a pixel-based coordinate system, and thus
    potentially not scalable.
  }
  \item{col}{
    The colour to apply to the light from \code{lightSource}.
  }
  \item{lightSource}{
    A light source object, produced by one of
    \code{\link{feDistantLight}}, \code{\link{fePointLight}}, or
    \code{\link{feSpotLight}}.
  }
  \item{\dots}{
    Further arguments to be passed onto \code{\link{fe}}.
  }
}
\details{
  For more information about this primitive, consult the reference to
  the SVG specification.
}
\value{
  An \code{fe.diffuse.lighting} object.
}
\references{
  \url{http://www.w3.org/TR/SVG/filters.html#feDiffuseLightingElement}
}
\author{
  Simon Potter
}
\seealso{
  \code{\link{filterEffect}} \code{\link{fe}},
  \code{\link{feDistantLight}}, \code{\link{fePointLight}},
  \code{\link{feSpotLight}}.
}