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

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עם כל השיפורים

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

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

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

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}

Light Source Attenuation

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

Specular Reflection

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

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.

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

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);

Material