2.3At the lowest level of processing, we manipulate bits in the framebuffer. In

Question

2.3At the lowest level of processing, we manipulate bits in the framebuffer. In WebGL, we can create a virtual framebuffer in our application as a two- dimensional array. You can experiment with simple raster algorithms, such as drawing lines or circles, through a function that generates a single value in the array. Write a small library that will allow you to work in a virtual frame- buffer that you create in memory. The core functions should be WritePixel and ReadPixel. Your library should allow you to set up and display your vir- tual framebuffer and to run a user program that reads and writes pixels using gl.POINTS in gl.drawArrays. 2.4 Turtle graphics is an alternative positioning system that is based on the concept of a turtle moving around the screen with a pen attached to the bottom of its shell. The turtle’s position can be described by a triplet (x, y, ), giving the location of the center and the orientation of the turtle. A typical API for such a system includes functions such as the following: init(x,y,theta); // initialize position and orientation of turtle forward(distance); right(angle); left(angle); pen(up_down); Implement a turtle graphics library using WebGL. All this using Html file

Explanation / Answer

Two & three dimensions scenes Drawing in two dimensions plane is a special case of 3Ddrawing • Viewer at the origin • View direction: positive z axis • Orthogonal (parallel)projection • Specifying the objects in XY (z=0) plane OpenGL drawing includes • Points • Line segments • Polygons Each primitive is completely specified by points in the 3D (called vertices) How we can specify a vertex? Warning: this is a draft copy. It has not been passed any revision Vertex specification • glVertex***(); • The first * could be 2 (z=0), 3(3D) or 4 (Homogeneous) to denote the number of coordinates • The second star could be i for integer, f for float, or d for double • The third star could be v for passing coordinates in an array or null for giving the coordinates directly • Instead of using c standard types use GL types • Use Glint instead of int • Use Glfloat instead of float • Use Gldouble instead of double, an so on Warning: this is a draft copy. It has glV«rt«x3f (x,y,0) ; glV«rtex2£(x t y); glVertex2i (GLint xi. GLlnt yi) glVertex3f(GLfloat x, CLfloat y, GLfloat z) GLflo&t vortex [3] gl Vert ex3f v (vertex) glBegin(CL.LIMES); glVertex3f(xl,yl,zl); glVertex3f (x2,y2,z2) ; glEndO, glBegin(GL_POIMTS); glVertex3f (xl.yl.zl); glVertex3f (x2 # y2,z2); glEndO ; been passed any revision OpenGL function classification • Primitive functions • Attribute functions • Viewing functions • Transformation functions • Input functions • Control functions • Query functions Warning: this is a draft copy. It has not been passed any revision OpenGL libraries • OpenGL core library - OpenGL32 on Windows - GL on most unix/linux systems (libGL.a) • OpenGL Utility Library (GLU) - Provides functionality in OpenGL core but avoids having to rewrite code (use OpenGL to provide complex tasks) • Links with window system - GLX for X window systems - WGL for Windows - AGLfor Macintosh Warning: this is a draft copy. It has not been passed any revision GLUT

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