Graphics Libraries
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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.
![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();](https://image.slidesharecdn.com/graphicslibraries-150318031407-conversion-gate01/85/Graphics-Libraries-10-320.jpg)
Graphics Libraries
- 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
- 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