The document discusses various graphics libraries used for 3D rendering. It describes PHIGS, the first standard for 3D graphics, and its features including a scene graph and centralized structure store. OpenGL is introduced as the most widely adopted library, providing a programming interface and graphics pipeline. Direct3D is presented as Microsoft's API for Windows, focused on gaming performance. Key differences between OpenGL and Direct3D are portability, functionality, and performance.

1. Graphics Libraries
Presented By:
Prachi Mishra

2. Contents
Overview
Common Graphics Libraries
PHIGS
Features of PHIGS
OpenGL
OpenGL Pipeline
Commands
Direct3D
How’s Direct3D Different?
Conclusion
References
03
04
05
06
07
08
09
14
15
16
17

3. Overview
• Today 3D graphics tools provide new methods in engineering,
medicine, entertainment and technology
• These are selected from exhaustive online research
• Incorrect selection can lead to undesired results
• A graphics library is a software interface to graphics hardware
commonly called the APIs
• It provides a set of graphics commands and functions which can
specify primitive geometric models and their attributes to digitize
and display

4. Common Graphics Libraries
A graphics programmer is should be able to program in at least one of
the following:
• OpenGL
• Direct3D
• PHIGS (Programmer's Hierarchical Interactive Graphics System)
• GKS (Graphics Kernel System)

5. PHIGS (Programmer's Hierarchical Interactive
Graphics System)
• An API standard for rendering 3D computer graphics through 1980s
• Available as a standalone implementation like IBM’s GraPHIGS or
Sun’s SunPHIGS
• Became a standard by 1990s ( ANSI and ISO)
• Supports only the most basic 3D graphics, including basic geometry
and meshes
• A combination of features of PHIGS and power led to the rise
of OpenGL

6. Features of PHIGS
• Included a scene graph which is a data structure for storing logical
sequences
• Had a CSS (Centralized Structure Store) i.e. a database for storing
primitives and their attributes
• CSSes were shared under workstations to give views
• Simple working:
Model built into CSS Workstation created and opened  Model
connected

7. OpenGL (Open Graphics Library)
• Most widely adopted graphics API
• Easy to use, well documented
• Cross platform and cross language
• Everything is primitive (can accept only simple shapes and sizes)
• Largely built on C but can be used in most programming languages

8. OpenGL Graphics Pipeline

9. void display(void)
{
int x, y;
//a. generate a random point
x = rand() %Width;
y = rand() % Height;
//b. specify a drawing color: red
glColor3f(1, 0, 0);
//c. specify to draw a point
glBegin(GL_POINTS);
glVertex2i (x,y);
glEnd();
//d. start drawing
glFlush();
}
Basic Commands for Drawing and Shape
void drawtriangle(float *v1, float *v2, float *v3)
{
glBegin(GL_TRIANGLES);
glVertex3fv(v1);
glVertex3fv(v2);
glVertex3fv(v3);
glEnd();
}

10. Commands for Transformation
glPushMatrix();
glLoadIdentity ();
glRotatef (alpha, 0.0, 0.0, 1.0);
drawArm (O, A);
glTranslatef (A[0], A[1], 0.0);
glRotatef (beta, 0.0, 0.0, 1.0);
glTranslatef (-A[0], -A[1], 0.0);
drawArm (A, B);
glPopMatrix();

11. Viewing
static void
reshape(int w, int h)
{
//a.specify modeling
coordinates
glMatrixMode
(GL_PROJECTION);
glLoadIdentity ();
glOrtho(left, right,
bottom, top, new,
far);
}

12. Color and Lighting
• Different colors for different vertices of the model can be
specified
• Light sources can be put to give different colors at different
positions in the environment, so the model can have overall
brightness, dull reflections, and/or shiny spots
• Lighting can be achieved by calculating the color of a pixel
• The normal of the pixel, the position of the viewer, and the
colors and positions of the light sources inherently decide
the lighting

13. Transparency
▪ Used for transparent objects by implementing transmission
coefficients for overlapping objects
▪ A final pixel’s R,G or B value depends on the blending of the
corresponding R, G, or B values of the pixels in the
overlapping objects through the transmission coefficients:
Iλ = a1Iλ1 + a2 Iλ2, where λ is R, G, or B; Iλ the blended color
component, a1 the transmission coefficient of the pixel in
the first object, and Iλ1 the color of the first object.

14. Direct3D
• Graphics API for Microsoft Windows
• Used to render 3D applications where performance is important
like gaming environments
• Implemented onWindows family of operating systems
• Also on embedded versions of Xbox family of video game
consoles

15. How’s Direct3D Different?
▪ Portability – OpenGL is cross platform while Direct3D is Windows
centric
▪ User Functionality – Direct3D is 3D hardware interface while
OpenGL is 3D rendering system that could be hardware accelerated
▪ Performance – Direct3D is more suitable when performance is
considered because of lighter codes
▪ Users/Applications – OpenGL has always seen more number of
users. Direct3D is mostly used for computer games

17. References
▪ http://www.opengl.org
▪ http://mohammadshakergtr.wordpress.com/
▪ http://graphics.wikia.com/wiki/Direct3D_vs._OpenGL
▪ http://slideshare.net/OpenGL_Basics
▪ https://ilias.fhv.at/goto_ilias_fhv_at_file_225344_download
.html