doc/ctsim-sgp.tex

   1 \chapter{Simple Graphics Package}\label{sgp}\index{Simple Graphics Package}
   2 \setheader{{\it Appendix \thechapter}}{}{}{\ctsimheadtitle}{}{{\it Appendix \thechapter}}%
   3 \ctsimfooter%
   4
   5 Simple Graphics Package was created in 1980 by Kevin Rosenberg and
   6 is modelled after the hypothetical graphics library described by Foley and van
   7 Dam\cite{FOLEY82}. It is designed to be platform-independent.
   8
   9 \section{Transformation Sequence}
  10 \latexonly{
  11 \parbox{11cm}{
  12 \centerline{Master coordinate (MC) level}
  13 \centerline{$\downarrow$}
  14 \centerline{Apply \emph{Current transformation matrix}}
  15 \centerline{$\downarrow$}
  16 \centerline{World coordinate (WC) level}
  17 \centerline{$\downarrow$}
  18 \centerline{Clipping against Window}
  19 \centerline{$\downarrow$}
  20 \centerline{Convert to Normalized device coordinates (NDC)}
  21 \centerline{$\downarrow$}
  22 \centerline{Clipping against Viewport}
  23 \centerline{$\downarrow$}
  24 \centerline{Convert to Physical device coordinates (PDC)}
  25 }}
  26 \latexignore{
  27 \centerline{Master coordinate (MC) level}
  28 \centerline{Apply \emph{Current transformation matrix}}
  29 \centerline{World coordinate (WC) level}
  30 \centerline{Clipping against Window}
  31 \centerline{Convert to Normalized device coordinates (NDC)}
  32 \centerline{Clipping against Viewport}
  33 \centerline{Convert to Physical device coordinates (PDC)}
  34 }
  35
  36 \section{Functions}%
  37
  38 \subsection{Master coordinate functions}
  39 \begin{twocollist}
  40 \twocolitem{\texttt{setWindow(xmin,ymin,xmax,ymax)}}{Set window for world
  41 coordinates}
  42 \twocolitem{\texttt{moveAbs(x,y)}}{Move graphics cursor to absolute position}
  43 \twocolitem{\texttt{moveRel(dx,dy)}}{Move graphics cursor relative to current position}
  44 \twocolitem{\texttt{pointAbs(x,y)}}{Draw point at current position}
  45 \twocolitem{\texttt{pointRel(dx,dy)}}{Draw point relative to current position}
  46 \twocolitem{\texttt{lineAbs(x,y)}}{Draw line from current position to
  47 absolute position}
  48 \twocolitem{\texttt{lineRel(dx,dy)}}{Draw line from current position to position
  49 relative to current position}
  50 \twocolitem{\texttt{markerAbs(x,y)}}{Draw marker at current position}
  51 \twocolitem{\texttt{markerRel(dx,dy)}}{Draw marker relative to current position}
  52 \twocolitem{\texttt{polylineAbs(x[],y[],n)}}{Draw a series of lines to absolute position}
  53 \twocolitem{\texttt{polylineRel(dx[],dy[],n)}}{Draw series of lines relative to current position}
  54 \twocolitem{\texttt{drawString(str)}}{Draw text string at current positon}
  55 \twocolitem{\texttt{drawCircle(r)}}{Draw circle at current positon}
  56 \twocolitem{\texttt{drawArc(r,start,stop)}}{Draw arc with center at current positon}
  57 \twocolitem{\texttt{drawRect(xmin,ymin,xmax,ymax)}}{Draw rectangle}
  58 \end{twocollist}
  59
  60 \subsection{Normalized coordinate functions}%
  61 \begin{twocollist}
  62 \twocolitem{\texttt{Viewport(xmin,ymin,xmax,ymax)}}{Viewport for window
  63 in NDC}
  64 \twocolitem{\texttt{stylus(x,y,beam)}}{Draw a line from current
  65 position if beam = 1, otherwise move stylus to new position}
  66 \twocolitem{\texttt{markerNDC(xndc,yndc)}}{Draw marker at NDC position}
  67 \end{twocollist}
  68
  69 \subsection{Master coordinate to World coordinate transformations}%
  70 These transformation functions operate on the \emph{Current transformation
  71 matrix} (CTM).
  72
  73 \begin{twocollist}
  74 \twocolitem{\texttt{clearCTM()}}{Sets the CTM to an identity matrix}
  75 \twocolitem{\texttt{preTranslate(x,y)}}{Apply translation to CTM}
  76 \twocolitem{\texttt{postTranslate(x,y)}}{Apply translation to CTM}
  77 \twocolitem{\texttt{preScale(x,y)}}{Apply scale to CTM}
  78 \twocolitem{\texttt{postScale(x,y)}}{Apply scale to CTM}
  79 \twocolitem{\texttt{preRotate(angle)}}{Apply rotation to CTM}
  80 \twocolitem{\texttt{postRotate(angle)}}{Apply rotation to CTM}
  81 \twocolitem{\texttt{preShear(x,y)}}{Apply shear to CTM}
  82 \twocolitem{\texttt{postShear(x,y)}}{Apply shear to CTM}
  83 \end{twocollist}
  84
  85 \subsection{Coordinate transformation functions}%
  86 \begin{twocollist}
  87 \twocolitem{\texttt{transformMCtoNDC(\&x,\&y)}}{Convert from master
  88 coordinates to NDC}
  89 \twocolitem{\texttt{transformNDCtoMC(\&x,\&y)}}{Convert from NDC to master
  90 coordinates}
  91 \end{twocollist}
  92
  93 \subsection{State functions}
  94 \begin{twocollist}
  95 \twocolitem{\texttt{eraseWindow()}}{Clears the screen}
  96 \twocolitem{\texttt{setColor(color)}}{Set current pen color}
  97 \twocolitem{\texttt{setLinestyle(style)}}{Set current pen style}
  98 \twocolitem{\texttt{setLinewidth(width)}}{Set current pen width}
  99 \twocolitem{\texttt{setTextColor(foreground, background)}}{Set text colors}
 100 \twocolitem{\texttt{setMarker(type,color)}}{Set marker attibutes}
 101 \twocolitem{\texttt{setRasterOp(rasterOp)}}{Set raster operator}
 102 \end{twocollist}
 103
 104 \section{Coordinate Mapping}
 105
 106 \subsection{Dimensions}
 107 Window (World Coordinates):  $X_{wmin}, X_{wmax}, Y_{wmin}, Y_{wmax}$ \\
 108 Viewport (Normalized Device Coordinates): $X_{vmin}, X_{vmax}, Y_{vmin}, Y_{vmax}$\\
 109 Physical (Physicial Device Coordinates): $X_{pmax}, Y_{pmax}$\\
 110
 111 \subsection{Formulas}
 112 To convert from Master coordinates to World coordinates: \\
 113 \centerline{Apply \emph{current transformation matrix}}
 114
 115 To convert from WC to NDC:\\
 116 \begin{equation}
 117 X_{ndc} = X_{vmin} + (X_{vmax} - X_{vmin})  (X_{wc} - X_{wmin}) / (X_{wmax} - X_{wmin})
 118 \end{equation}
 119 \begin{equation}
 120 Y_{ndc} = Y_{vmin} + (Y_{vmax} - Y_{vmin}) (Y_{wc} - Y_{wmin}) / (Y_{wmax} - Y_{wmin})
 121 \end{equation}
 122
 123 To convert from NDC to PDC:
 124 \begin{equation}
 125      X_{pdc} = X_{ndc} X_{pmax}
 126 \end{equation}
 127 \begin{equation}
 128      Y_{pdc} = X_{ndc} Y_{pmax}
 129 \end{equation}