Cmpe 466 computer graphics. Graphics output primitives. (Chapter 4)

Output primitives and reference frames

Output primitives are functions that we use

Screen coordinates

Screen coordinates (integers): Locations on a video monitor
Coordinates correspond to

Specifying a 2D WC reference frame

Figure 4-2 World-coordinate limits for a

OpenGL point functions

glBegin (GL_POINTS);
glVertex2i (50, 100);
glVertex2i (75, 150);
glVertex2i

OpenGL point functions: alternative code

int point1 [ ] = {50, 100};
int

More on point functions

Specifying positions in 3D using floating-point coordinates
Using class

OpenGL line functions

Figure 4-4 Line segments that can be displayed in

Polygon Fill Areas

Figure 4-8 A convex polygon (a), and a concave

Identifying concave polygons

Figure 4-9 Identifying a concave polygon by calculating cross-products

Splitting concave polygons: vector method

Form the edge vectors Ek=Vk+1 - Vk
Calculate

Splitting example

Figure 4-10 Splitting a concave polygon using the vector method.

Splitting polygons

Splitting a convex polygon into a set of triangles

Triangles make several

Inside-outside tests

Odd-even rule
Draw a line from any position P to a

Nonzero winding-number rule

Object edges and the line must be vectors
Count the

Inside-outside test examples

Figure 4-12 Identifying interior and exterior regions of a

Variations of nonzero winding-number rule

Figure 4-13 A fill area defined as

Variations of nonzero winding-number rule

Figure 4-14 A fill area defined as

Variations of nonzero winding-number rule

Figure 4-15 A fill area defined as

Polygon tables

Figure 4-16 Geometric data-table representation for two adjacent polygon surface

Plane equations

Often, information about spatial orientation of surface components is needed
This

Solutions to plane equations

We obtain A, B, C, and D by

Solutions

Then

Front and back polygon faces

Faces can be determined by the sign

OpenGL polygon fill-area functions

Figure 4-22 Displaying polygon fill areas using a

Fill-area examples

Quadrilateral fill-areas

Figure 4-23 Displaying quadrilateral fill areas using a list of

A complex scene might require hundreds or thousands of OpenGL calls!

Figure

Using a vertex array

Figure 4-25 Subscript values for array pt corresponding

Display lists

const double TWO_PI = 6.2831853;
GLuint regHex;
GLdouble theta;
GLint x, y, k;
/*