SER332 Lecture 19

Introduction to Graphics and Game Development
Lighting
(201804)

Transcript

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   SER332
   Introduction to Graphics and Game
   Development
   Lecture 19: Lighting
   Javier Gonzalez-Sanchez
   javiergs@asu.edu
   PERALTA 230U
   Office Hours: By appointment
   

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2. Javier Gonzalez-Sanchez | SER332 | Spring 2018 | 2
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   Lighting
   § By default, OpenGL's fixed-function pipeline implements the Blinn-Phong
   Shading Model.
   § Three steps to activate OpenGL fixed-function pipeline lighting:
   1. Enable light source(s) and define their attributes
   (position, ambient, diffuse, specular).
   1. Define normal vectors
   2. Define materials
   

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3. Javier Gonzalez-Sanchez | SER332 | Spring 2018 | 3
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   Enable Light Source | init method
   // light position
   // Point light: w component is 1.0
   // Directional light: w component is 0.0
   Glfloat light_position[] = {-1.0, 0.0, 1.0, 0.0};
   // light configuration
   glLightfv( GL_LIGHT0, GL_POSITION, light_position);
   // Enable lighting + each individual light!!!
   glEnable(GL_LIGHTING);
   glEnable(GL_LIGHT0);
   

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4. Javier Gonzalez-Sanchez | SER332 | Spring 2018 | 4
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   Moving Light Sources | display method
   glPushMatrix();
   gluLookAt(0.0, 0.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
   glPushMatrix();
   glRotated(spin, 1.0, 0.0, 0.0);
   glLightfv(GL_LIGHT0, GL_POSITION, light_position);
   glPopMatrix()
   // draw something else here
   glPopMatrix();
   

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5. Javier Gonzalez-Sanchez | SER332 | Spring 2018 | 5
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   Ambient + Diffuse + Specular
   § Ambient
   It is a constant term.
   Applies equally to all points on the object
   § Ambient + Diffuse
   Diffuse color of light interacts with diffuse component
   of material. Its intensity depends on the angle
   between the light source and the surface normal
   § Ambient + Diffuse + Specular
   Specular color of light interacts with specular component
   of material. Its intensity depends on the angle
   between the viewer and the direction of a ray reflected
   from the light source.
   

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6. Javier Gonzalez-Sanchez | SER332 | Spring 2018 | 6
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   Light Source’s Attributes
   Peter Wonka
   

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7. Javier Gonzalez-Sanchez | SER332 | Spring 2018 | 7
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   Example (original code without lighting)
   § https://github.com/javiergs/SER332/blob/master/Lecture19/original.cpp
   

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8. Javier Gonzalez-Sanchez | SER332 | Spring 2018 | 8
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   Example (update one)
   void init () {
   …
   // RGBA
   GLfloat light_ambient[] = { 0.0, 0.0, 0.0, 1.0 };
   GLfloat light_diffuse[] = { 1.0, 1.0, 1.0, 1.0 };
   GLfloat light_specular[] = { 1.0, 1.0, 1.0, 1.0 };
   GLfloat light_position[] = { 1.0, 1.0, 1.0, 0.0 };
   // what kind of light source?
   glLightfv(GL_LIGHT0, GL_AMBIENT, light_ambient);
   glLightfv(GL_LIGHT0, GL_DIFFUSE, light_diffuse);
   glLightfv(GL_LIGHT0, GL_SPECULAR, light_specular);
   glLightfv(GL_LIGHT0, GL_POSITION, light_position);
   // enable
   glEnable(GL_LIGHT0);
   glEnable(GL_LIGHTING);
   }
   

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9. Javier Gonzalez-Sanchez | SER332 | Spring 2018 | 9
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   Example (update one)
   § https://github.com/javiergs/SER332/blob/master/Lecture19/light.cpp
   

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10. Javier Gonzalez-Sanchez | SER332 | Spring 2018 | 10
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    Add Normals
    § Per Face Normals
    § Per Vertex Normals
    § Per Vertex Weight Normals
    

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11. Javier Gonzalez-Sanchez | SER332 | Spring 2018 | 11
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    Example (update two)
    struct Mesh {
    // vertex
    vector dot_vertex;
    vector dot_normalPerFace;
    vector dot_normalPerVertex;
    vector dot_texture;
    // faces
    vector face_index_vertex;
    vector face_index_normalPerFace;
    vector face_index_normalPerVertex;
    vector face_index_texture;
    };
    

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    Javier Gonzalez-Sanchez | SER332 | Spring 2018 | 12
    // normal per face
    void calculateNormalPerFace(Mesh* m) {
    Vec3 v1, v2, v3, v4, v5;
    for (int i = 0; i < m->face_index_vertex.size(); i += 3) {
    v1 = m->dot_vertex[m->face_index_vertex[i]];
    v2 = m->dot_vertex[m->face_index_vertex[i + 1]];
    v3 = m->dot_vertex[m->face_index_vertex[i + 2]];
    v4 = (v2 - v1);
    v5 = (v3 - v1);
    v4 = v4.cross(v5);
    v4.normalize();
    m->dot_normalPerFace.push_back(v4);
    int pos = m->dot_normalPerFace.size() - 1;
    // same normal for all vertex in this face
    m->face_index_normalPerFace.push_back(pos);
    m->face_index_normalPerFace.push_back(pos);
    m->face_index_normalPerFace.push_back(pos);
    }
    }
    

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13. Javier Gonzalez-Sanchez | SER332 | Spring 2018 | 13
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    Example (update two)
    § https://github.com/javiergs/SER332/blob/master/Lecture19/light.cpp
    

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14. Javier Gonzalez-Sanchez | SER332 | Spring 2018 | 14
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    Example (update three)
    // calculate normal per vertex
    void calculateNormalPerVertex(Mesh* m) {
    m->dot_normalPerVertex.clear();
    m->face_index_normalPerVertex.clear();
    Vec3 suma; suma.x = 0; suma.y = 0; suma.z = 0;
    //initialize
    for (unsigned int val = 0; val < m->dot_vertex.size(); val++) {
    m->dot_normalPerVertex.push_back(suma);
    }
    // calculate sum for vertex
    for (long pos = 0; pos < m->face_index_vertex.size(); pos++) {
    m->dot_normalPerVertex[m->face_index_vertex[pos]] +=
    m->dot_normalPerFace[m->face_index_normalPerFace[pos]];
    }
    // normalize for vertex
    for (unsigned int val = 0; val < m->dot_normalPerVertex.size(); val++) {
    m->dot_normalPerVertex[val] = m->dot_normalPerVertex[val].normalize();
    }
    //normalVertexIndex is the same that vertexIndex
    for (unsigned int pos = 0; pos < m->face_index_vertex.size(); pos++) {
    m->face_index_normalPerVertex.push_back(m->face_index_vertex[pos]);
    }
    }
    

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15. Javier Gonzalez-Sanchez | SER332 | Spring 2018 | 15
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    Per Vertex Normal
    § https://github.com/javiergs/SER332/blob/master/Lecture19/light.cpp
    

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    SER332 Introduction to Graphics
    Javier Gonzalez-Sanchez
    javiergs@asu.edu
    Spring 2018
    Disclaimer. These slides can only be used as study material for the class SER332 at ASU. They cannot be distributed or used for another purpose.
    

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