Computer Graphics
(Undergraduate)

2002 Autumn
Assignment #1

Projection, HSR, and Shading

Objective: Viewing projection, Z Buffer, Gouraud shading, OpenGL

Due: 10/21, 2002

Program Description:

You are required to implement an OpenGL program that does viewing projection, Z Buffer, and Gouraud shading based on Phong model. There are two kinds of data, one is viewing data (*.view), and the other is object data (*.obj).

Viewing Data (*.view):

Viewing data describes lights, viewing parameters, and viewport information. We assume that the view coordinate system is a right-handed coordinate system (the viewing direction is negtive Z direction in view coordinate system) and the projection is perspective. The data format is described below:

light x y z ar ag ab dr dg db sr sg sb

(x,y,z): light POSITION (no "w" term, because We assume they are all point lights).
(ar,ag,ab): light AMBIENT property.
(dr,dg,db): light DIFFUSE property.
(sr,sg,sb): light SPECULAR property.

**ATTENTION: There might be multiple light sources.

ambient r g b

(r,g,b): the GLOBAL AMBIENT term.

[Hint: use glLightModel... ]

eye x y z

(x,y,z): your eye position.

vat x y z

(x,y,z): the position you are looking at

vup x y z

(x,y,z): your up vector.

fovy angle

angle: your field of view angle.

dnear d

d: The distance between your eye and near plane.

dfar f

f: The distance between your eye and far plane.

viewport x y width height

(x,y): The lower left corner of the viewport rectangle.
width: viewport width.
height: viewport height.

[Hint: your should set view frustum and viewport information in GLUT Reshape callback function].

 

Object Data (*.obj):

Object Data defines a set of polygons and each polygon could have its own material property specified by a material name defined in the material library file (*.mtl).

Ex:

box.obj
 Description
g Box01
mtllib ./box.mtl
v -2.5 -2.5 10
v -2.5 2.5 10
v 2.5 2.5 10
v 2.5 -2.5 10
v -2.5 -2.5 15
v 2.5 -2.5 15
v 2.5 2.5 15
v -2.5 2.5 15
# 8 verticies
vn 0 0 -1
vn 0 0 1
vn 0 -1 0
vn 1 0 0
vn 0 1 0
vn -1 0 0
# 6 normals
vt 0 0
vt 0 1
vt 1 1
vt 1 0
# 4 texture coordinates
usemtl m1
f 1/1/1 2/2/1 3/3/1
f 3/3/1 4/4/1 1/1/1
usemtl m2
f 5/1/2 6/2/2 7/3/2
f 7/3/2 8/4/2 5/1/2
usemtl m3
f 1/1/3 4/2/3 6/3/3
f 6/3/3 5/4/3 1/1/3
usemtl m1
f 4/1/4 3/2/4 7/3/4
f 7/3/4 6/4/4 4/1/4
usemtl m2
f 3/1/5 2/2/5 8/3/5
f 8/3/5 7/4/5 3/1/5
usemtl m3
f 2/1/6 1/2/6 5/3/6
f 5/3/6 8/4/6 2/1/6		 g obj_name: specify the object name
mtllib filename: specify the material library file
v x y z: define the position of a set of vertex.
The first vertex is indexed by 1 and subsequent vertices
are numbered sequentially





# comment: indicate this line is a comment
vn x y z: define a set of normal vector.
The first normal vector is indexed by 1 and
subsequent vertices are numbered sequentially




vt u v: define a set of texture coordinate




usemtl material_name: specify which material defined
in the material library file you want to use.


f v1/t1/n1 v2/t2/n2 v3/t3/n3: define a polygon
consisted of 3 vertex.
(v1,v2,v3) is the index of vertex positoin array for
each vertex.
(t1,t2,t3) is the index of texture coordinate array for
each vertex.
(n1,n2,n3) is the index of normal vector array for
each vertex.

For more information about *.obj, see the webpage:
http://netghost.narod.ru/gff/graphics/summary/waveobj.htm

 

box.mtl
 Description
# Max2Mtl Version 4.0 Mar
newmtl m1
Ka 0.0 0.0 0.0
Kd 1.0 0 1.0
Ks 0.3 0.3 0.3
d 1.0
Ns 2.2
illum 2

newmtl m2
Ka 0.0 0.0 0.0
Kd 0.0 1 0.0
Ks 0.3 0.3 0.3
d 1.0
Ns 2.2
illum 2

newmtl m3
Ka 0.0 0.0 0.0
Kd 0.0 0.0 1.0
Ks 0.3 0.3 0.3
d 1.0
Ns 2.2
illum 2

 # comment: indicate this line is a comment
newmtl material_name: create a new material
Ka r g b: define the AMBIENT term
Kd r g b: define the DIFFUSE term
Ks r g b: define the SPECULAR term
d value: see the reference.
Ns value: define the Phong specular component.
illum value: see the reference.

For more information about *.mtl, see the webpage:
http://pub33.ezboard.com/fnendowingsmiraifrm19.showMessage?topicID=28.topic

 

In order to make you concentrate on writing OpenGL code, we provide a loader to help you load *.obj file. You can simply add the loader (mesh.cpp, mesh.h) to your workspace, and use the class named mesh to load *.obj file.

The class mesh has members as follows:

Members
 Description
class material {
float Ka[4];
float Kd[4];
float Ks[4];
float Ns;
}

class Vertex {
int v;
int n;
int t;
int m;
}

class Vec3 {
float ptr[3];
}

class FACE {
Vertex v[3];
}

material mat[100];
vector<Vec3> vList;
vector<Vec3> nList;
vector<Vec3> tList;
vector<FACE> faceList;
int vTotal;
int nTotal;
int tTotal;
int fTotal;

 The material property






The vertex property
 v: index of vList
n: index of nList
t: index of tList
m: index of mat[100]










mat[100]: an array of all materials.
vList: an array of all vertex position.
nList: an array of all normal vector.
tList: an array of all texture coordinate.
faceList: an array of all faces (polygons).
vTotal: the number of vertices.
nTotal: the number of normal vectors.
tTotal: the number of texture coordinate.
fTotal: the number of faces.

So, here is an example to load an object file:

#include "mesh.h"
mesh *object;
             
main()
{
    object = new mesh("box.obj");
    delete object; 
}

and after you loaded the object file, you can use

for (int i=0;i<object->fTotal;i++)
{
   for (int j=0;j<3;j++)
   {
      object->mat[object->faceList[i][j].m].Ka
      or
      object->nList[object->faceList[i][j].n].ptr
      or
      object->vList[object->faceList[i][j].v].ptr
      or
      ......
   }
}

to access each polygon data directly.


**ATTENTION: If you are using VC++ 6.0, you may encounter about 100+ warning messages because of the Microsoft bug:

http://support.microsoft.com/default.aspx?scid=KB;EN-US;Q167355&

So I suggest you to modify your setting

Project->Settings->C/C++->General->Warning level->None

to get rid of the annoying messages.

 

Sample Input:

There are four test cases. You can download it to test your program. Your program should be designed as flexible as possible. My suggestion is that you can design your program to receive two command line arguments as view data file and scene data file.

**Ex: prog1.exe box.view box.obj.

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