Shading and two type of shading flat shading and gauraud shading with coding exampe

Presented by Adil

how to install openGL package• open visual studio and click on tools tab

2nd:select library package manager and click package manager console

3rd:console window will appear at the bottom of screen and write the

following commandInstall-Package freeglut

see next slide

[email protected] Adiil (Mcs)

install-package freeglut

what is shading?• The appearance of lights and darks found in a

work of art.• In computer graphics, shading is a method used

to create or enhance the illusion of depth in an image by varying the amount of darkness in the image. As you can see, three levels of shading are used in the example of a rectangular object, thus making it appear to be three dimensional. Shading can also be used to make some objects appear to be in front of or behind

other objects in the image

some real word examples

Type of shading

• Flat shading– glShadeModel(GL_FLAT)

• Smooth (Gouraud) shading– glShadeModel(GL_SMOOTH)

Flat Shading• The simplest shading algorithm, called flat shading,

consists of using an illumination model to determine the corresponding intensity value for the incident light, then shade the entire polygon according to this value. Flat shading is also known as constant shading or constant intensity shading. Its main advantage is that it is easy it implement.

• In the case of curved objects, when the surface changes gradually and the light source and viewer are far from the surface.

• In general, when there are large numbers of plane surfaces.

• when problem is not light, some thing else

Gourand Shading

• This shading algorithm was first described by H. Gouraud in 1971. It is also called bilinear intensity interpolation. Gouraud shading is easier to understand in the context of the scan-line algorithm used in hidden surface removal, For now, assume that each pixel is examined according to its horizontal (scan-line) placement

• here edges are visible• In modern graphics hardware, gourand shading is

probably at least as fast as flat shading,and faster than phong shading.

• Gouraud is enabled by default

complete coding#include <Gl/glut.h>

void Draw() {glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glEnable(GL_DEPTH_TEST);

// Set material propertiesGLfloat qaBlack[] = {0.0, 0.0, 0.0, 1.0};GLfloat qaGreen[] = {0.0, 1.0, 0.0, 1.0};GLfloat qaRed[] = {1.0, 0.0, 0.0, 1.0};GLfloat qaBlue[] = {0.0, 0.0, 1.0, 1.0};GLfloat qaWhite[] = {1.0, 1.0, 1.0, 1.0};GLfloat qaLowAmbient[] = {0.2, 0.2, 0.2, 1.0};GLfloat qaFullAmbient[] = {1.0, 1.0, 1.0, 1.0};

for (int iIndex = 0; iIndex < 2; ++iIndex) {if (iIndex == 0) {

glShadeModel(GL_FLAT);} else {

glShadeModel(GL_SMOOTH);}

//Set, ambient, diffuse and specular lighting. Set ambient to 20%.glMaterialfv(GL_FRONT, GL_AMBIENT, qaGreen);glMaterialfv(GL_FRONT, GL_DIFFUSE, qaGreen);glMaterialfv(GL_FRONT, GL_SPECULAR, qaWhite);glMaterialf(GL_FRONT, GL_SHININESS, 128.0);glLightfv(GL_LIGHT0, GL_AMBIENT, qaLowAmbient);

// Draw a sphereglMatrixMode(GL_MODELVIEW);glLoadIdentity();glPushMatrix();

glTranslatef(-0.5 + (float)iIndex, 0.5, -2.0);glutSolidSphere(.5, 20, 20);

glPopMatrix();

// Turn off diffuse and specular reflection. Set ambient light to full.glMaterialfv(GL_FRONT, GL_DIFFUSE, qaBlack);glMaterialfv(GL_FRONT, GL_SPECULAR, qaBlack);glLightfv(GL_LIGHT0, GL_AMBIENT, qaFullAmbient);

// Draw a triangle with one red, green, and blue vertex.glBegin(GL_TRIANGLES);

glMaterialfv(GL_FRONT, GL_AMBIENT, qaRed);glVertex3f(-.5 + (float)iIndex, 0.0, -.2);glMaterialfv(GL_FRONT, GL_AMBIENT, qaGreen);glVertex3f(-.933 + (float)iIndex, -.75, -.2);glMaterialfv(GL_FRONT, GL_AMBIENT, qaBlue);glVertex3f(-.067 + (float)iIndex, -.75, -.2);

glEnd();}

glFlush();}

void Initialize() {glClearColor(0.0, 0.0, 0.0, 0.0);glMatrixMode(GL_PROJECTION);glLoadIdentity();glOrtho(-1.0, 1.0, -1.0, 1.0, -3.0, 3.0);

// Lighting set upglLightModeli(GL_LIGHT_MODEL_LOCAL_VIEWER, GL_TRUE);glEnable(GL_LIGHTING);glEnable(GL_LIGHT0);

// Set lighting intensity and colorGLfloat qaAmbientLight[] = {0.2, 0.2, 0.2, 1.0};GLfloat qaDiffuseLight[] = {0.8, 0.8, 0.8, 1.0};GLfloat qaSpecularLight[] = {1.0, 1.0, 1.0, 1.0};glLightfv(GL_LIGHT0, GL_AMBIENT, qaAmbientLight);glLightfv(GL_LIGHT0, GL_DIFFUSE, qaDiffuseLight);glLightfv(GL_LIGHT0, GL_SPECULAR, qaSpecularLight);

// Set the light positionGLfloat qaLightPosition[] = {0.0, 1.0, -.5, 1.0};glLightfv(GL_LIGHT0, GL_POSITION, qaLightPosition);

}

int main(int iArgc, char** cppArgv) {glutInit(&iArgc, cppArgv);glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);glutInitWindowSize(250, 250);glutInitWindowPosition(200, 200);glutCreateWindow("XoaX.net");Initialize();glutDisplayFunc(Draw);glutMainLoop();return 0;

}

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