lecture04-1

0j 00 00 10 gltranslatef 30 00 00 drawbolt

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Unformatted text preview: system draw_wheel( ); for (j=0; j<5; j++) { glPushMatrix (); glRotatef(72.0*j, 0.0, 0.0, 1.0); glTranslatef (3.0, 0.0, 0.0); draw_bolt ( ); glPopMatrix ( ); R RT RTv Global – Bottom Up Start Trans Rot Matrix Manipulation – Example Matrix Local coordinate system draw_wheel( ); for (j=0; j<5; j++) { glPushMatrix (); glRotatef(72.0*j, 0.0, 0.0, 1.0); glTranslatef (3.0, 0.0, 0.0); draw_bolt ( ); glPopMatrix ( ); R RT RTv Local – Top Down Start Rot Trans OpenGL: Conventions Functions in OpenGL start with gl gl Functions • Most functions just gl (e.g., glColor()) Most glColor() • Functions starting with glu are utility functions (e.g., Functions glu gluLookAt()) gluLookAt() • Functions starting with glx are for interfacing with the X Functions glx Windows system (e.g., in gfx.c) Windows OpenGL: Conventions Function names indicate argument type and number • Functions ending with f take floats Functions • Functions ending with i take ints Functions • Functions ending with b take bytes Functions • Functions ending with ub take unsigned bytes Functions ub • Functions that end with v take an array. Functions Examples • glColor3f() takes 3 floats • glColor4fv() takes an array of 4 floats glColor4fv() takes OpenGL: Conventions Variables written in CAPITAL letters • Example: GLUT_SINGLE, GLUT_RGB • usually constants • use the bitwise or command (x | y) to combine constants OpenGL: Simple Use Open a window and attach OpenGL to it Set projection parameters (e.g., field of view) Setup lighting, if any Main rendering loop • Set camera pose with gluLookAt() Set – Camera position specified in world coordinates • Render polygons of model – Simplest case: vertices of polygons in world coordinates OpenGL: Simple Use Open a window and attach OpenGL to it • glutCreateWindow() or FLTK window method OpenGL: Perspective Projection Set projection parameters (e.g., field of view) Typically, we use a perspective projection perspective • Distant objects appear smaller than near objects Distant • Vanishing point at center of screen • Defined by a view frustum (draw it) Defined view Other projections: orthographic, isometric Other orthographic isometric Setting up Camera glMatrixMode(GL_MODELVIEW); glLoadIdentity(); gluLookAt( eyeX, eyeY, eyeZ, eyeX, lookX, lookY, lookZ, upX, upY, upZ); upX, • eye[XYZ]: camera position in world coordinates • look[XYZ]: a point centered in camera’s view • up[XYZ]: a vector defining the cam...
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