1. ייצוג בעולם 3D ייצוג מצולעים (פוליגונים) צלע קודקוד צלעe0 : {v1,v2}
משולש V1
קודקוד T1 e3 e0 T2
צלעe0 : {v1,v2} T0 V0
משולשT2 :{v0,v1,v2} T3 e1 e2

2. דוגמאות

3. כך זה נראה בגדול

4. נוסיף צבע לעולם

5. ועוד תאורה ...

6. נעדן את התאורה ..

7. עכשיו זה נראה בסדר

8. עם כל השיפורים

9. Illumination and Shading
Reflection
Specular
Light in
How to shade a surface
Position (Light/Surface)
Orientation (Light/Surface)
Characteristics (Light/Surface)
Local Illumination Models
Individual point and
The light source/s Illuminate it
Global Illumination Models
The light source and
The interchange of light between all the surfaces
Reflection
(diffuse)
Internal
Reflection
Transmitted
Light
emission

10. Ambient Light Non reflective Self-luminous Illumination equation
I is the resulting intensity
Ki is the object’s intrinsic intensity
An ambient illumination variable is associated with each point
Evaluating the ambient equation <==> Lighting the object.
I = k i

11. Diffuse Reflection Point light source
The brightness depends on the angle q between direction to the light L and the surface normal N
If the light bean
Has cross sectional deferential are dA
It intercepts an area dA/cos(q) of the surface. q
I = I k cos(q)
p d N q N dA
dA/cos(q ) S2 S1

12. Combining Shading Models
Series of pictures of sphere illuminated by diffuse reflection
model only using different Kd values (0.4, 0.55, 0.7, 0.85,1.0).
Series of pictures of sphere illuminated by ambient and diffuse reflection
model. Ia = Ib = 1.0, Kd = 0.4 and Ka = {0.0, 0.15, 0.30, 0.45, 0.60}

13. Light Source Attenuation

14. Specular Reflection Phone Illumination N L R V   I = Ia Ka +
Developed by Phong Bui-Toung for nonperfect
reflection. The model assumes that the maximum
specular reflection occurs when  is zero and falls
off sharply as  increases. The rapid falloff is
approximated by cos () . V    n
I = Ia Ka +
fatt Id [KdOd cos() +W()cos ()] n
Od :Object diffuse factor.
W():Factor of specular reflection light

15. Specular Reflection

16. Shading Models for Polygons
We can shade a surface by calculating the surface normal at each visible
point and applying the desired model at that point.
Constant Flat Shading
Applies an illumination model one to determine a singles intensity value
that is then used to shade the entire polygon.
Interpolated Shading
Shading information is linearly interpolated across triangle from illumination
values determined at it vertices

17. Polygon Mesh Shading
Gouraud Shading extends the concept of interpolated shading applied
to individual polygons by interpolating polygon vertex illumination values
that take into account the surface being approximated.
A vertex intensity is computed by using the vertex
normal with any desired shading model.
Phong Shading interpolates the surface normal vector, rather
than the intensity. Interpolation occurs across a polygon span on a
scan line.

18. Interpolated Shading Problems
Polygonal Silhouette
Perspective distortion
Orientation dependence
Problem at shared vertices
Inaccurate vertex normal

19. Light & Material in OpenGL
GLfloat lit_mbient[] = {0.2, 0.2, 0.2, 1.0};
GLfloat lit_diffuse[] = {1.0, 1.0, 1.0, 1.0};
GLfloat lit_specular[] = {1.0, 1.0, 1.0, 1.0};
GLfloat lit_position[] = {-2.0, 1.0, 3.0, 1.0};
GLfloat lit_spot_dir[] = {-1.0, -1.0, -1.0};
GLfloat lit_shine[] = {50.0};
glShadeModel(GL_SMOOTH);
glEnable(GL_LIGTING);
glEnable(GL_LIGHT0);
glLightfv(GL_LIGHT0, GL_POSITION, lit_ position);
glLightfv(GL_LIGHT0, GL_AMBIENT, lit_ ambient);
glLightfv(GL_LIGHT0, GL_DIFFUSE, lit_diffuse);
glLightfv(GL_LIGHT0, GL_SPECULAR, lit_specular);
glLightfv(GL_LIGHT0, GL_SHININESS, lit_shine);

20. Material