Other Geometric Primitives

1
Other Geometric Primitives
2
Agenda

• Polygon Fill Area Functions
• Raster Functions
• Display Lists

3
Learning Objectives

• Understand OpenGL functions related to polygon
  fill areas, raster manipulation, and display
  lists.

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Fill-Area Primitives

• Fill-area
• Area filled with a certain color
• Most often the shape is that of a polygon
• Boundaries are linear
• Surface tesselation is a curved surface
  approximated with polygon facets (surface fitting
  with polygon mesh)
• Standard graphic objects are objects made of a
  set of polygon surface patches.

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Polygons

• Polygon classification
• Polygon is a planar shape having a
  closed-polyline boundary and no edge crossing
• Convex polygon has all interior angles less than
  or equal to 180º, line joining two interior
  points is also interior to the polygon
• Concave polygon otherwise
• Degenerate polygon describes a set of vertices
  that are collinear
• Polygons may not be planar.

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Polygon Fill-Areas

• Polygon example (hexagon)
• Polygon is a planar shape having a
  closed-polyline boundary and no edge crossing
• gl.glBegin (GL.GL_POLYGON)
• for (k 0 k lt 6 k)
• theta TWO_PI k / 6.0
• hexVertex.x circCtr.x 150 cos
  (theta)
• hexVertex.y circCtr.y 150 sin
  (theta)
• gl.glVertex2i (hexVertex.x, hexVertex.y)
• gl.glEnd ( )

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Polygon Fill-Areas

• Other polygon examples
• Triangle (GL_TRIANGLES or GL_TRIANGLE_STRIP or
  GL_TRIANGLE_FAN)
• Rectangle (GL_RECT, where means d, f, i, s, v)
• Quadrilateral (GL_QUADS or GL_QUAD_STRIP)

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Raster Functions

• Raster operations
• Assigning a color to an array of pixels
  (pixmap)glDrawPixels (width, height, data
  format, data type, pixMap)
• ExampleglDrawPixels (128, 128, GL_RGB,
  GL_UNSIGNED_BYTE, colorShape)where colorShape
  is an array of pixels of size 128 x 128

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Raster Functions

• Raster operations
• Reading an array of pixels (pixmap)glReadPixels
  (xmin, ymin, width, height, dataFormat, dataType,
  array)
• dataFormat (GL_RGB, GL_BLUE, )
• dataType (GL_BYTE, GL_INT, GL_FLOAT, )
• glCopyPixels (xmin, ymin, width, height,
  pixelValues)

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Character Functions

• Characters
• Size
• Type (font, or typeface) (Times, Courier, )
• Serif (small lines or accents at the end of the
  character strokes), more readable
• Sans serif (no accent), more legible (easy to
  recognize)
• Monospace / proportional (width varies)
• Bitmap font (represented by pixels), raster font
• Postscript font (filling-in outline)

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Character Functions

• OpenGL character functions
• glutBitmapCharacter (font, character)
• Font (GLUT_BITMAP_TIMES_ROMAN_10, )
• Character (A, , a, ) or ASCII code (65, ,
  97, )
• glutStrokeCharacter (font, character)
• Font (GLUT_STROKE_ROMAN, GLUT_STROKE_MONO_ROMAN)

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Display Lists

• A display list provides a name for a sequence of
  statements.
• List creationglNewList(listID,
  listMode)glEndList()listID positive
  integerlistMode GL_COMPILE or
  GL_COMPILE_AND_EXECUTE

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Display Lists

• Automatic ID generationlistID glGenLists(1)
• List executionglCallList(listID)
• List deletionglDeleteLists(startID, nLists)