Characters, Display Lists

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Characters, Display Lists

• Soon Tee Teoh
• CS 116A

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Drawing Characters

• Often need to display text
• Classification
• Typeface Different designs eg.
• Courier, Times Roman, Arial, Microsoft Sans Serif
• Font Typeface and size fixed eg.
• 28-point Courier italic

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Serif and sans-serif

• Two broad groups of typeface serif and
  sans-serif, eg.
• Palatino serif
• Lucina Sans sans serif
• Notice that sans serif does not have extra
  flourishes at the end of strokes.
• Serif is easier to read lots of. Sans serif is
  easier to recognize single characters

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Proportionally-spaced or constant-spaced

• Is this proportionally-spaced or constant spaced?
• XGMXXKWWW
• iiitttlll

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Computer Representation

• 2 types
• Bitmap (raster)
• Outline (stroke,vector)
• Bitmap fonts represented as bitmaps
• Need one bitmap for each style
• Multiples of pixel size
• Blocky when expanded
• Outline fonts Represented as curve functions
• Slow needs to be rasterized
• Flexible size can be adjusted, good quality

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OpenGL Character Functions

• For bitmapped fonts can use
• glRasterPos2i(x,y)
• font GLUT_BITMAP_9_BY_15
• characterb
• glutBitmapCharacter(font, character)
• glutBitmapCharacter(font, o)
• For Stroke Characters you can use
• fontGLUT_STROKE_MONO_ROMAN
• glutStrokeCharacter(font,b)

Stroke Character example (function to draw a
string)
void output(GLfloat x, GLfloat y, char text)
char p glPushMatrix() glTranslatef(x,
y, 0) for (p text p p)
glutStrokeCharacter(GLUT_STROKE_ROMAN, p)
glPopMatrix()
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OpenGL Characters
Note For stroke characters, the maximum top
character in the font is 119.05 units the bottom
descends 33.33 units. For GLUT_STROKE_MONO_ROMAN,
each character is 104.76 units wide.
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OpenGL Display Lists

• Store some set of OpenGL commands
• Then you can call it later at any time, eg.
• Make display list describing scene
• Then call the list using different viewing
  parameters

GLuint ID ID glGenLists(1) glNewList (ID,
GL_COMPILE) // or GL_COMPILE_AND_EXECUTE glE
ndList() glCallList(ID)
glColor3f(1.0,0.0,0.0) glBegin(GL_QUADS) glVertex
3f(1.0,0.0,0.0) glVertex3f(1.0,1.0,0.0) glVertex
3f(0.0,1.0,0.0) glVertex3f(0.0,0.0,0.0) glEnd()