GRAFIKA KOMPUTER - M. Ali Fauzi | PTIIK Universitas...

GRAFIKA KOMPUTER~ M. Ali Fauzi

DrawingPrimitive Objects

Recall

Although you can draw complex and interestingpictures using OpenGL,they’re all constructed from a small number of primitive graphical items.

Recall

This shouldn’t be too surprising—look at what Leonardo da Vinciaccomplished with just pencils and paintbrushes.

A DRAWING SURVIVAL KIT

Clearing the Window

On a computer, the memory holding the picture is usually filled with the last picture you drew, so you typically need to clear it to some background color before you start to draw the new scene.

Clearing the Window

glClearColor(0.0f, 0.0f, 0.0f, 1.0f);

glClear(GL_COLOR_BUFFER_BIT);

// Set background color to black and opaque// Clear the color buffer

Specifying a ColorFor example, the pseudocodeset_current_color(red);

draw_object(A);

draw_object(B);

set_current_color(green);

set_current_color(blue);

draw_object(C);

draws objects A and B in red, and object C in blue. The command on thefourth line is wasted.

Forcing Completion of Drawing

glFlush();

OrglFinish();

OrglutSwapBuffers();

Coordinate System Survival KitglutReshapeFunc(reshape);

void reshape(int w, int h)

{

glViewport(0,0,(GLsizei) w, (GLsizei) h);

glMatrixMode(GL_PROJECTION);

glLoadIdentity();

gluOrtho2D(0.0, (GLdouble) w, 0.0,

(GLdouble) h);

}

Coordinate System glViewport() adjusts the pixel rectangle for drawing to be the entire new window. The next three routines adjust the coordinate system for drawing so that the lower left corner is (0, 0) and the upper right corner is (w, h)

Coordinate System

OPENGL GEOMETRIC DRAWING PRIMITIVES

Geometric Primitives

The geometry is specified by vertices.There are ten primitive types

Use glBegin()/glEnd() :

glBegin(Glenum mode);

// some vertices, color, etc

glEnd();


glBegin(GL_QUADS);

glColor3f(1.0f, 0.0f, 0.0f);

glVertex2f(-0.5f, -0.5f);

glVertex2f( 0.5f, -0.5f);

glVertex2f( 0.5f, 0.5f);

glVertex2f(-0.5f, 0.5f);

glEnd();


Between glBegin/ glEnd, those openglcommands are allowed:

glVertex*() : set vertex coordinates

glColor*() : set current color

glTexCoord*(): set texture

coordinates (Texture)

Points, GL_POINTS

> Individual points> Point size can be altered

glPointSize (float size)

Points, GL_POINTS

glPointSize( 0.5 );

glBegin(GL_POINTS);

glColor3f( 0.1, 0.0, 0.0 );

glVertex2f( -0.9, 0 );

glVertex2f( -0.4, 0.4 );

glVertex2f( 0.0, 0.9 );

glVertex2f( 0.4, 0.4 );

glVertex2f( 0.9, 0 );

glVertex2f( 0.4, -0.4 );

glVertex2f( 0, -0.9 );

glVertex2f( -0.4, -0.4 );

glEnd();

Lines, GL_LINES

> Pairs of vertices interpreted as individual line segments> Can specify line width using:

glLineWidth (float width)

Lines, GL_LINES

glLineWidth( 0.5 );

glBegin(GL_LINES);

glColor3f( 0.0, 0.0, 0.0 );


glVertex2f( -0.4, 0.4 );

glVertex2f( 0.0, 0.9 );

glVertex2f( 0.4, 0.4 );


glVertex2f( 0.4, -0.4 );


glVertex2f( -0.4, -0.4 );

glEnd();

Line Strip, GL_LINE_STRIP

Series of connected line segments

glLineWidth( 0.5 );

glBegin(GL_LINE_STRIP);

glColor3f( 0.0, 0.0, 0.0 );


glVertex2f( -0.4, 0.4 );

glVertex2f( 0.0, 0.9 );

glVertex2f( 0.4, 0.4 );


glVertex2f( 0.4, -0.4 );


glVertex2f( -0.4, -0.4 );

glEnd();

Line Strip, GL_LINE_STRIP

Line Loop, GL_LINE_LOOP

Line strip with a segment added between last and first vertices

glLineWidth( 0.5 );

glBegin(GL_LINE_LOOP);

glColor3f( 0.0, 0.0, 0.0 );


glVertex2f( -0.4, 0.4 );

glVertex2f( 0.0, 0.9 );

glVertex2f( 0.4, 0.4 );


glVertex2f( 0.4, -0.4 );


glVertex2f( -0.4, -0.4 );

glEnd();

Line Loop, GL_LINE_LOOP

Polygon, GL_POLYGON

Boundary of a simple, convex polygon

glBegin(GL_POLYGON);

glColor3f( 0.0, 0.1, 0.1 );


glVertex2f( -0.4, 0.4 );

glVertex2f( 0.0, 0.9 );

glVertex2f( 0.4, 0.4 );


glVertex2f( 0.4, -0.4 );


glVertex2f( -0.4, -0.4 );

glEnd();

Polygon, GL_POLYGON

Triangles, GL_TRIANGLES

Triples of vertices interpreted as triangles

glBegin(GL_TRIANGLES);

glColor3f( 0.0, 0.1, 0.1 );


glVertex2f( -0.4, 0.4 );

glVertex2f( 0.0, 0.9 );

glVertex2f( 0.4, 0.4 );


glVertex2f( 0.4, -0.4 );


glVertex2f( -0.4, -0.4 );

glEnd();

Triangles, GL_TRIANGLES

Triangle Strip,GL_TRIANGLE_STRIP

Linked strip of triangles

v0

v2

v1

v3

v4 v5

v6v7

glBegin(GL_TRIANGLE_STRIP);

glColor3f( 0.0, 0.1, 0.1 );


glVertex2f( -0.4, 0.4 );

glVertex2f( 0.0, 0.9 );

glVertex2f( 0.4, 0.4 );


glVertex2f( 0.4, -0.4 );


glVertex2f( -0.4, -0.4 );

glEnd();

Triangle Strip,GL_TRIANGLE_STRIP

Triangle Fan,GL_TRIANGLE_FAN

Linked fan of triangles

v0

v1 v2

v3v4

v5

glBegin(GL_TRIANGLE_FAN);

glColor3f( 0.0, 0.1, 0.1 );


glVertex2f( -0.4, 0.4 );

glVertex2f( 0.0, 0.9 );

glVertex2f( 0.4, 0.4 );


glVertex2f( 0.4, -0.4 );


glVertex2f( -0.4, -0.4 );

glEnd();

Triangle Fan,GL_TRIANGLE_FAN

Quads, GL_QUADS

Quadruples of vertices interpreted as four-sided polygons

glBegin(GL_QUADS);

glColor3f( 0.0, 0.1, 0.1 );


glVertex2f( -0.4, 0.4 );

glVertex2f( 0.0, 0.9 );

glVertex2f( 0.4, 0.4 );


glVertex2f( 0.4, -0.4 );


glVertex2f( -0.4, -0.4 );

glEnd();

Quads, GL_QUADS

Quad Strip,GL_QUAD_STRIP

Linked strip of quads

glBegin(GL_QUAD_STRIP);

glColor3f( 0.0, 0.1, 0.1 );


glVertex2f( -0.4, 0.4 );

glVertex2f( 0.0, 0.9 );

glVertex2f( 0.4, 0.4 );


glVertex2f( 0.4, -0.4 );


glVertex2f( -0.4, -0.4 );

glEnd();

Quad Strip,GL_QUAD_STRIP

Stippled Lines

To make stippled (dotted or dashed) lines, you use the commandglLineStipple() to define the stipple pattern, and then you enable linestippling with glEnable().

glLineStipple(1, 0x3F07);

glEnable(GL_LINE_STIPPLE);

Stippled Lines

Drawing CircleGLfloat jari_jari=150;

// Titik Pusat

GLfloat a = 290, b = 250 ;

GLfloat x=a+jari_jari, y=b;

glLineWidth(7);

glBegin(GL_LINE_LOOP);

for(float teta=0;teta<=360;teta++){

GLfloat x_aksen = (x-a)*cos((teta/180)*(22/7)) -

((y-b)*sin((teta/180)*(22/7))) + a;

GLfloat y_aksen = (x-a)*sin((teta/180)*(22/7)) -

((y-b)*cos((teta/180)*(22/7))) + b;

glVertex2i(x_aksen,y_aksen);

}

glEnd();

Drawing Starsint s; // ukuran titik

float x,y; // posisi titik

for(int i=0;i<1000;i++){

s=rand()%4+1;

glPointSize(s);

glBegin(GL_POINTS);

x=-100+200*(float)rand()/RAND_MAX;

y=-100+200*(float)rand()/RAND_MAX;

glVertex2f(x,y);

glEnd();

}

Tugas

> Draw Circle, Ellips, Cardioid, Treeleaf, Spiral, Limacon and Rain> Write Down the Docs> Format PDF

Tugas

> Send to [email protected]

> Subject GRAFKOM_[KELAS]_NIM_Tug

as2_PrimitiveObjects

PLAGIARISM =ZERO

Cheers, Old Sport~ M. Ali [email protected]

GRAFIKA KOMPUTER - M. Ali Fauzi | PTIIK Universitas...

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