Some more stuff.

[ipdf/documents.git] / LitReviewDavid.tex

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@@ -36,8 +36,29 @@ to issues with numeric precision.
 
 \section{Rendering}
 
-As existing displays (and printers) are bit-mapped devices, one of the core problems which must be solved when
-designing a document format is how it is to be \emph{rasterized} into a bitmap at a given resolution.
+Computer graphics comes in two forms: bit-mapped (or raster) graphics, which is defined by an array of pixel colours, 
+and \emph{vector} graphics, defined by mathematical descriptions of objects. Bit-mapped graphics are well suited to photographs
+and are match how cameras, printers and monitors work. However, bitmap devices do not handle zooming beyond their
+``native'' resolution --- the resolution where one document pixel maps to one display pixel ---, exhibiting an artefact
+called pixelation where the pixel structure becomes evident. Attempts to use interpolation to hide this effect are
+never entirely successful, and sharp edges, such as those found in text and diagrams, are particularly effected.
+
+Vector graphics lack many of these problems: the representation is independent of the output resolution, and rather
+an abstract description of what it is being rendered, typically as a combination of simple geometric shapes like lines,
+arcs and ``B\'ezier curves''. 
+As existing displays (and printers) are bit-mapped devices, vector documents must be \emph{rasterized} into a bitmap at
+a given resolution. This bitmap is then displayed or printed. The resulting bitmap is then an approximation of the vector image
+at that resolution.
+
+This project will be based around vector graphics, as these properties make it more suited to experimenting with zoom
+quality.
+
+
+The rasterization process typically operates on an individual ``object'' or ``shape'' at a time: there are special algorithms
+for rendering lines\cite{bresenham1965algorithm}, triangles\cite{giesen2013triangle}, polygons\cite{pineda1988parallel} and B\'ezier
+Curves\cite{goldman_thefractal}. Typically, these are rasterized independently and composited in the bitmap domain using Porter-Duff
+compositing\cite{porter1984compositing} into a single image. This allows complex images to be formed from many simple pieces, as well
+as allowing for layered translucent objects, which would otherwise require the solution of some very complex constructive geometry problems.
 
 \subsection{Compositing Digital Images\cite{porter1984compositing}}