Chapter 3 Viewing

Contents Overview: The Camera Analogy Viewing and Modeling Transformation Projection Transformation Viewport Transformation

Chapter Objectives View a geometric model in any orientation Control the location in 3D space Clip Undesired portions of the model

Overview -The Camera Analogy-

Overview: The Camera Analogy Viewing Transformation Positioning the view volume in the world Modeling Transformation Positioning models in the world Projection Transformation Determining the shape of the view volume Viewport Transformation

Method for Transformation - 1 The Viewing Transformation glTranslatef(); glRotatef(); gluLookAt(); The Modeling Transformation glScalef();

Method for Transformation - 2 The Projection Transformation Perspective Orthographic Order of Setting glMatrixMode(types) glLoadIdentity() glFrustum() or gluPerspective(), glOrtho()

General-Purpose Transformation Commands glMatrixMode(GLenum mode) Specifies which matrix will be modified GL_MODELVIEW, GL_PROJECTION, GL_TEXTURE glLoadIdentity() Sets the currently modifiable matrix to the 4*4 identity matrix

General-Purpose Transformation Commands glMultMatrix{fd}(const Type *m) Multiply the current matrix by the matrix passed in as an argument glLoadMatrix{fd}(const Type *m) Set the 16 values of the current matrix to those specified by m

Viewing and Modeling Transformations

Thinking about Transformation To performing viewing or modeling transformation glMatrixMode(GL_MODELVIEW);

2 Types of Coordinate System Example glMatrixMode(GL_MODELVIEW); glloadIdentity(); glMultiMatrixf(N); glMultiMatrixf(M); glBegin(GL_POINTS); glVertex3f(v); glEnd(); Grand, Fixed Coordinate System Moving a Local Coordinate System

Modeling Transformation Translate Void glTranslate{fd}(x, y, z); Rotate Void glRotate{fd}(angle, x, y, z); Scale Void glScale{fd}(x, y, z); glScalef(2.0, -1.5, 1.0);

Viewing Transformation - 1 glTranslate() or glRotate() Moving forward camera = Moving Backward Object gluLookAt() Void gluLookAt( eyex, eyey, eyez, centerx, centery, centerz, upx, upy, upz);

Viewing Transformation - 2 Creating a Custom Utility Routine Void PilotView(GLdouble planex, Gldouble planey, Gldouble planez, Gldouble roll, Gldouble pitch, Gldouble heading) { glRotated(roll, 0.0, 0.0, 1.0); glRotated(pitch, 0.0, 1.0, 0.0); glRotated(heading, 1.0, 0.0, 0.0); glTranslated(-planex, -planey, -planez); }

Projection Transformations

Projection Transformations Purpose To define a viewing volume How an object is projected onto the screen How to Clip the object Setting for projection transformation glMatrixMode(GL_PROJECTION); glLoadIdentity();

Perspective Projection - 1 Foreshortening The farther, the smaller object appears in the final image glFrustum(left, right, bottm, top, near, far)

Perspective Projection - 2 gluPerspective(fov, aspect, near, far)

Orthographic Projection -1 View Volume Rectangular parallelepiped

Orthographic Projection -2 glOrtho(left, right, bottom, top, near, far) glOrtho2D (left, right, bottom, top)

Viewport Transformation

Defining the Viewport glViewport(x, y, width, height) gluPerspective(fov, 2.0, near, far); glViewport(0, 0, 400, 200); The Transformed Depth coordinates

Program Demo Transformation\lesson1.exe