Specifying Vertices Examples:     glVertex2s(2, 3);  glVertex3d(0.0, 0.0, 3.1415926535898); glVertex4f(2.3, 1.0, -2.2, 2.0);  GLdouble dvect[3] = {5.0, 9.0, 1992.0};  glVertex3dv(dvect);

	Drawing  primitives glBegin() / glEnd() pair surround glVertex() calls   glBegin(GL_POLYGON);    glVertex2f(0.0, 0.0);    glVertex2f(0.0, 3.0);    glVertex2f(4.0, 3.0);    glVertex2f(6.0, 1.5);    glVertex2f(4.0, 0.0); glEnd();    Figure 2-6

Primitive Specification GL_POINTS             individual points GL_LINES              pairs of vertices interpreted as                           individual segments GL_LINE_STRIP         series of connected line segments GL_LINE_LOOP          same as above, with a segment added                           between last and first vertices GL_TRIANGLES          triples of vertices interpreted as                           triangles GL_TRIANGLE_STRIP     linked strip of triangles GL_TRIANGLE_FAN       linked fan of triangles GL_QUADS              quadruples of vertices interpreted                           as four-sided polygons GL_QUAD_STRIP         linked strip of quadrilaterals GL_POLYGON            boundary of a simple, convex polygon

	Primitive Specification (cont) Figure 2-7

	Vertex specification    color/texture, etc. specifications reflect the current state of the OpenGL state machine.  Vertices are only generated by a glVertex() call. glBegin(GL_POINTS); glColor3f(0.0, 1.0, 0.0); /* green */ glColor3f(1.0, 0.0, 0.0); /* red */ glVertex(...); glColor3f(1.0, 1.0, 0.0); /* yellow */ glColor3f(0.0, 0.0, 1.0); /* blue */ glVertex(...);

	State Management  State variables specify OpenGL rendering qualities such as: Color Texture Lighting  Most states are turned off by default  Turning on these variables can be expensive but can improve the image quality greatly  State variables are changed with glEnable() or glDisable()  Values can be queried by glGet() calls (p. 50)

	Displaying Points, Lines, and Polygons By default: Polygons are filled Points are one-pixel Lines are solid, one-pixel wide    glPointSize() specifies the width of a point If anitaliasing is enabled, a circular group of pixels is drawn If antialiasing is disabled screen-aligned rectangular pixels are drawn (fractional pixels are rounded to integer values)

Specifying line parameters glLineWidth() specifies the width of lines NOTE! With nonantialiased wide lines, the line width isn't measured perpendicular to the line. Instead, it's measured in the y direction if the absolute value of the slope is less than 1.0; otherwise, it's measured in the x direction. The rendering of an antialiased line is exactly equivalent to the rendering of a filled rectangle of the given width, centered on the exact line.

Stippled Lines Figure 2-8 To make stippled (dotted or dashed) lines, you use the command glLineStipple() to define the stipple pattern, and then you enable line stippling with glEnable(). glLineStipple(1, 0x3F07); glEnable(GL_LINE_STIPPLE); void glLineStipple(GLint factor, GLushort pattern); Sets the current stippling pattern for lines.  The pattern argument is a 16-bit series of 0s and 1s, and it's repeated as necessary to stipple a given line. A 1 indicates that drawing occurs, and 0 that it does not, on a pixel-by-pixel basis, beginning with the low-order bit of the pattern.

	Stippled Lines (cont) Figure 2-9  Beware!  The OpenGL state machine can be simplistic (i.e. stoopid)