Presented by:
Abhishek Sanghvi
Anurag Bhagwat
Mitali Bhende
Vikrant Khadilkar

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GENERATION OF A DETAILED 3D ENVIRONMENT
Problem Statement
Create a detailed 3D model of the college building. A user should be able to move through the virtual environment with complete 360 degree motion of the user camera. Creation of the environment will include the tasks of surface generation, texturing, lighting and shading, and hidden surface detection.
MOTIVATION
A virtual tour of the college using a 3D model of the same will serve to help those unacquainted with the college environment (eg. new students).
It will also serve as a 3d college map.
This same technique can be extended to sightseeing places and historical landmarks.
Tools Used
Visual C++ 2008 – For coding
OpenGL(Open Graphics Library)
provides the programmer with an interface to graphics hardware
powerful, low-level rendering and modeling software library, available on all major platforms, with wide hardware support.
GLUT(OpenGL Utility Tools)
OpenGL does not directly support any form of windowing, menus, or input
GLUT provides basic functionality in all of those areas, while remaining platform independent
BLOCK DIAGRAM
SURFACE GENERATION
Dimensions obtained by survey of the real world model
Dimensions will be mapped into a co-ordinate system in the 3D world.
Co-ordinates will be used to define vertices
Using vertices as reference, standard OpenGL functions will be used to render surfaces.
Co-ordinates will not be hard-wired in order to allow flexibility.
TEXTURE MAPPING
In computer graphics, the application of a type of surface to a 3D image.
A texture can be uniform, such as a brick wall, or irregular, such as wood grain or marble.
The common method is to create a 2D bitmapped image of the texture, called a "texture map," which is then "wrapped around" the 3D object
Textures will be obtained from images of the real world model
TEXTURE MAPPING PROCESS
1. create a texture object -- glGenTextures;
2. specify a texture for the texture object:
1. load the texture image from a file (or generate it on the fly);
2. bind the texture image to the texture object -- glTexImage2D;
3. specify texture parameters -- glTexParameter;
4. use the texture object:
1. enable texture mapping -- glEnable(GL_TEXTURE_2D);
2. bind the texture object to the context -- glBindTexture;
3. draw the scene and map the texture to vertices -- glTexCoord;
HIDDEN SURFACE DETECTION (CULLING)
Process used to determine which surfaces and parts of surfaces are not visible from a certain viewpoint.
Hidden surface determination is necessary to render an image correctly, so that one cannot look through walls in virtual reality, for example.
The process makes rendering objects quicker and more efficient by reducing the number of polygons for the program to draw.
ALGORTITHMS
They are fundamentally an exercise in sorting, and usually vary in the order in which the sort is performed and how the problem is subdivided. Sorting large quantities of graphics primitives is usually done by divide and conquer.
 Back face detection
 Painters Algorithm
 Area Subdivision Method
 Z-buffer
 Scan-line
Z-Buffer
 Store color and depth of closest surface for each pixel in frame buffer
 Scan convert updates only pixels whose interpolated depth is closer than the depth stored in the frame buffer
 Initially, set z buffer values to infinity
 Scan convert using the following WritePixel:
WritePixel(int x, int y, float z, colour) if ( z < zbuf[x][y] )
zbuf[x][y] = z;
frambuffer[x][y] = colour;
ADVANTAGES :
 Easy to implement
 Simple hardware implementation
 We don't need to load all polygons at once in order to run algorithm
 Device dependant
 High Memory Requirements
LIGHTING
Lighting algorithms are used to simulate effects like direct illumination and reflection in 3D computer graphics.
ALGORITHMS :
 Radiosity – for scenes with purely diffuse surfaces, computationally expensive.
 Ray tracing – for simulating wide variety of optical effects.
 Path tracing – ray tracing with infinite recursion depth; hence the slowest rendering method.
 Ambient occlusion – gives model a global illumination-like effect.
 Photon mapping - images that are indistinguishable from images taken of the real world
RAY TRACING
Ray tracing can be used to generate natural lighting effects like reflection, refraction, soft shadows, depth of field, motion blur.
Ray tracing is a technique for generating an image by tracing the path of light through pixels in an image plane and simulating the effects of its encounters with virtual objects.
Here each ray must be tested for intersection with some subset of all the objects in the scene. Once the nearest object has been identified, the algorithm will estimate the incoming light at the point of intersection, examine the material properties of the object, and combine this information to calculate the final color of the pixel.
When a ray hits a surface, it could generate up to three new types of rays: reflection, refraction, and shadow
SHADING
Shading refers to the process of altering a color based on its angle to lights and its distance from lights to create a photorealistic effect
TYPES OF LIGHTS
Ambient: No source point; affects all polygons independent of position, orientation and viewing
Diffuse: Light scattered in all directions after it hits a polygon; dependant upon incident angle
Specular: ‘Shininess’ ; dependant upon incident and viewing angles
SHADING MODELS
 Flat Shading : shades each polygon based on angle between normal and light source
 Gourad : computes an intensity for each vertex and then interpolates the computed intensities across the polygons
 Phong : Phong shading interpolates the surface normal, rather than the intensity
 Phong-Blinn : Phong shading modified to trade precision with computing efficiency
 Phong-Blinn is the default shading model used in OpenGL