OpenGL Programming Guide Second Edition - Niksula

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} glMatrixMode(GL_PROJECTION); glLoadIdentity(); glOrtho(−50.0, 50.0, −50.0, 50.0, −1.0, 1.0); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); void mouse(int button, int state, int x, int y) { } /* switch (button) { } case GLUT_LEFT_BUTTON: if (state == GLUT_DOWN) glutIdleFunc(spinDisplay); break; case GLUT_MIDDLE_BUTTON: if (state == GLUT_DOWN) glutIdleFunc(NULL); break; default: break; * Request double buffer display mode. * Register mouse input callback functions */ int main(int argc, char** argv) { } glutInit(&argc, argv); glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB); glutInitWindowSize (250, 250); glutInitWindowPosition (100, 100); glutCreateWindow (argv[0]); init (); glutDisplayFunc(display); glutReshapeFunc(reshape); glutMouseFunc(mouse); glutMainLoop(); return 0; OpenGL Programming Guide − Chapter 2, State Management and Drawing Geometric Objects − 18
Chapter 2 State Management and Drawing Geometric Objects Chapter Objectives After reading this chapter, you’ll be able to do the following: Clear the window to an arbitrary color Force any pending drawing to complete Draw with any geometric primitive⎯points, lines, and polygons⎯in two or three dimensions Turn states on and off and query state variables Control the display of those primitives⎯for example, draw dashed lines or outlined polygons Specify normal vectors at appropriate points on the surface of solid objects Use vertex arrays to store and access a lot of geometric data with only a few function calls Save and restore several state variables at once Although you can draw complex and interesting pictures using OpenGL, they’re all constructed from a small number of primitive graphical items. This shouldn’t be too surprising⎯look at what Leonardo da Vinci accomplished with just pencils and paintbrushes. At the highest level of abstraction, there are three basic drawing operations: clearing the window, drawing a geometric object, and drawing a raster object. Raster objects, which include such things as two−dimensional images, bitmaps, and character fonts, are covered in Chapter 8. In this chapter, you learn how to clear the screen and to draw geometric objects, including points, straight lines, and flat polygons. You might think to yourself, "Wait a minute. I’ve seen lots of computer graphics in movies and on television, and there are plenty of beautifully shaded curved lines and surfaces. How are those drawn, if all OpenGL can draw are straight lines and flat polygons?" Even the image on the cover of this book includes a round table and objects on the table that have curved surfaces. It turns out that all the curved lines and surfaces you’ve seen are approximated by large numbers of little flat polygons or straight lines, in much the same way that the globe on the cover is constructed from a large set of rectangular blocks. The globe doesn’t appear to have a smooth surface because the blocks are relatively large compared to the globe. Later in this chapter, we show you how to construct curved lines and surfaces from lots of small geometric primitives. This chapter has the following major sections: "A Drawing Survival Kit" explains how to clear the window and force drawing to be completed. It also gives you basic information about controlling the color of geometric objects and describing a coordinate system. "Describing Points, Lines, and Polygons" shows you what the set of primitive geometric objects is and how to draw them. "Basic State Management" describes how to turn on and off some states (modes) and query state variables. OpenGL Programming Guide − Chapter 2, State Management and Drawing Geometric Objects − 1
Page 1 and 2: OpenGL Programming Guide Second Edi
Page 3 and 4: Examples of Composing Several Trans
Page 5 and 6: Bitmaps and Fonts The Current Raste
Page 7 and 8: Chapter 12 Evaluators and NURBS Pre
Page 9 and 10: Implementation−Dependent Pixel De
Page 11 and 12: Rotation Perspective Projection Ort
Page 13 and 14: depth−cuing diffuse directional l
Page 15 and 16: RGBA mode server shading shininess
Page 17 and 18: To Tom Doeppner and Andy van Dam, w
Page 19 and 20: textures onto three−dimensional o
Page 21 and 22: geometry). Even if you have little
Page 23 and 24: Acknowledgments The second edition
Page 25 and 26: Chapter 1 Introduction to OpenGL Ch
Page 27 and 28: of motion. "Plate 8" shows the scen
Page 29 and 30: } glVertex3f (0.25, 0.75, 0.0); glE
Page 31 and 32: OpenGL as a State Machine OpenGL is
Page 33 and 34: is enabled and the primitive is a p
Page 35 and 36: If you are directly accessing a win
Page 37 and 38: glVertex3f (0.75, 0.75, 0.0); glVer
Page 39 and 40: human eye is only so good. The key
Page 41: Figure 1−3 Double−Buffered Rota
Page 45 and 46: appropriate size and location for a
Page 47 and 48: Chapter 5 for details on these topi
Page 49 and 50: Example 2−1 Reshape Callback Func
Page 51 and 52: See Figure 2−3 for some examples
Page 53 and 54: glVertex4f(2.3, 1.0, −2.2, 2.0);
Page 55 and 56: GL_LINES Draws a series of unconnec
Page 57 and 58: ones in blue, despite the extra col
Page 59 and 60: void glLineWidth(GLfloat width); Se
Page 61 and 62: void display(void) { int i; glClear
Page 63 and 64: GL_FILL to indicate whether the pol
Page 65 and 66: Figure 2−10 Constructing a Polygo
Page 67 and 68: 0xAA, 0xAA, 0xAA, 0xAA, 0x55, 0x55,
Page 69 and 70: glPolygonMode(GL_FRONT_AND_BACK, GL
Page 71 and 72: Figure 2−14 Six Sides; Eight Shar
Page 73 and 74: void glEdgeFlagPointer(GLsizei stri
Page 75 and 76: glEnableClientState (GL_VERTEX_ARRA
Page 77 and 78: process as few as eight vertices. (
Page 79 and 80: } else glColorPointer(sc, tc, str,
Page 81 and 82: GL_ALL_ATTRIB_BITS −− GL_COLOR_
Page 83 and 84: glBegin(GL_LINE_STRIP); for (i = 0;
Page 85 and 86: } out[0] = v1[1]*v2[2] − v1[2]*v2
Page 87 and 88: } } for (i = 0; i < 3; i++) { } v12
Page 89 and 90: Chapter 3 Viewing Chapter Objective
Page 91 and 92: the following. 1. Set up your tripo
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program, not necessarily the order
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} glViewport (0, 0, (GLsizei) w, (G
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interior spaces look when viewed fr
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Philosophy" in Chapter 7.) (OpenGL
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x−axis), if you want the object t
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shown in Figure 3−6. Figure 3−6
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glLoadIdentity(); glScalef(1.5, 0.5
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Figure 3−10 Separating the Viewpo
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Figure 3−12 Using gluLookAt() So,
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glMatrixMode(GL_PROJECTION); glLoad
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GLdouble near, GLdouble far); Creat
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planes and locate them wherever you
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(Chapter 10 discusses the depth buf
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{ } double radtheta, degtheta; radt
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Figure 3−21 Pushing and Popping t
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Advanced If you know enough mathema
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* clip left half −− x < 0 */ }
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#include #include #include stati
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Figure 3−25 Robot Arm You can use
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} } case ‘S’: shoulder = (shoul
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#include #include #include #incl
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Chapter 4 Color Chapter Objectives
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is called the color buffer. The siz
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number of bitplanes, 0.0 specifies
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Figure 4−4 A Color Map A painter
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mode. Then you must control the vis
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GL_FLAT. With flat shading, the col
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independent quad 4i Table 4−2 How
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"Real−World and OpenGL Lighting"
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desire a more accurate (or just dif
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Example 5−1 accomplishes these ta
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Example 5−1, the only element of
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GLfloat light_ambient[] = { 0.0, 0.
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Figure 5−2 GL_SPOT_CUTOFF Paramet
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A light position that remains fixed
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*/ void display(void) { } GLfloat p
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} gluLookAt (ex, ey, ez, 0.0, 0.0,
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it doesn’t matter what the back
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glMaterialfv(GL_FRONT_AND_BACK, GL_
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glTranslatef (1.25, 3.0, 0.0); glMa
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void display(void) { } glClear(GL_C
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colors when in RGBA mode. (See "The
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The diffuse term needs to take into
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of using this color ramp with a sin
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drawn in a window on the screen? Wh
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To blend three different images equ
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#include static int leftFirst = GL
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already in the framebuffer (the des
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} glPushMatrix (); glTranslatef (0.
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Figure 6−2 Aliased and Antialiase
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#include static float rotAngle = 0
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} glutDisplayFunc (display); glutMa
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} } rotAngle += 20.; if (rotAngle >
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#include #include #include #incl
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{ } switch (key) { } case ‘t’:
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} } glFogf (GL_FOG_DENSITY, 0.35);
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In these three equations, z is the
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} glFogf (GL_FOG_START, 1.0); glFog
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where m is the maximum depth slope
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Chapter 7 Display Lists Chapter Obj
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} } } } glEnd(); glVertex3f(x, y, z
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glEnd() calls are stored in the dis
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implementation may be able to perfo
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} return 0; The glTranslatef() rout
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arrays, so these operations can be
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mechanism requires that you put the
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} CP; int type; CP Adata[] = { }; {
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} glTranslatef(10.0, 30.0, 0.0); pr
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glEndList(); If you use the display
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Chapter 8 Drawing Pixels, Bitmaps,
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0xff, 0x00, 0xff, 0x00, 0xc0, 0x00,
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Drawing the Bitmap Once you’ve se
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an offset to every entry in the str
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{0x00, 0x00, 0x7e, 0xe7, 0xc3, 0xc3
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} glutMainLoop(); return 0; Images
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component, followed by a blue color
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current drawing buffers with glDraw
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Figure 8−8 glCopyTexImage*() and
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Figure 8−9 *SKIP_ROWS, *SKIP_PIXE
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Pixel Mapping All the color compone
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} int i, j, c; for (i = 0; i < chec
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} glutMotionFunc(motion); glutMainL
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3. Each component (R, G, B, A, or d
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5. If the storage format is one of
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lend a texture color with the surfa
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An Overview and an Example This sec
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#define checkImageHeight 64 static
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} init(); glutDisplayFunc(display);
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texture of internal format GL_R3_G3
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Note: There is one major limitation
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{ } switch (key) { } case ‘s’:
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GL_READ_BUFFER and are processed ex
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#include #include #include GLuby
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} glTexEnvf(GL_TEXTURE_ENV, GL_TEXT
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Figure 9−5 Texture Magnification
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eturned in textureNames do not have
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} GL_NEAREST); glTexParameteri(GL_T
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texture objects. void glPrioritizeT
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lended with the texture color in a
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the surface, the more distortion of
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Figure 9−8 Clamping a Texture You
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Initially in Example 9−6, equally
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} glFlush(); void reshape(int w, in
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calculated only at the time they’
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indexed by s’/q’ and t’/q’
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Figure 10−1 Region Occupied by a
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you might use them for saving an im
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can be one of the following: GL_FRO
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7. Logical operation Each of these
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You can obtain the values for all s
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} glPushMatrix(); glRotatef (90.0,
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pixel appears, it’s drawn only if
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Table 10−4 Sixteen Logical Operat
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} xwsize = right − left; ywsize =
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} glutSolidSphere (1.0, 16, 16); gl
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} glFlush(); void reshape(int w, in
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Example 10−5 Depth−of−Field E
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} } glAccum (GL_RETURN, 1.0); glFlu
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Chapter 11 Tessellators and Quadric
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hurts to be tidy. Tessellation Call
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void errorCallback(GLenum errorCode
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GLdouble value); For the tessellati
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The winding rules are also designed
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for several vertices may not get th
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The GLU provides a routine for obta
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GLUquadricObj* gluNewQuadric (void)
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sweepAngle are measured in degrees,
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} glTranslatef(0.0, 2.0, 0.0); glPu
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Chapter 12 Evaluators and NURBS Cha
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vertices can be used like any other
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} A cubic Bézier curve is describe
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You can use glEvalCoord1() with any
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}; {0.5, −1.5, −1.0}, {1.5, −
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Figure 12−3 Lit, Shaded Bézier S
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} for (i = 0; i < imageWidth; i++)
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once with the control points (ratio
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} glRotatef(330.0, 1.,0.,0.); glSca
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The default value for GLU_DISPLAY_M
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points, respectively. You might als
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Figure 12−6 Trimmed NURBS Surface
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Chapter 13 Selection and Feedback C
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As mentioned in the previous sectio
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void drawTriangle (GLfloat x1, GLfl
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} glPushMatrix (); glMatrixMode (GL
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different components of a primitive
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glMatrixMode (GL_PROJECTION); glPus
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} glPopMatrix(); /* draw last two w
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} if (mode == GL_SELECT) glLoadName
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} return 0; Try This Modify Example
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hand, selection in three dimensions
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A Feedback Example Example 13−7 d
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} glMatrixMode (GL_PROJECTION); glL
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Chapter 14 Now That You Know Chapte
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GL_STACK_OVERFLOW Command would cau
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extension that is available only on
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Each time through the loop, you cle
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} } set_color(i,j); glVertex2i(x(i,
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the bits of the appropriate color d
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C, ..., I, where region I is outsid
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Shadows Every possible projection o
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you’ll need to clear the stencil
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Figure 14−3 Dirichlet Domains If
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Video⎯Even if your machine doesn
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from specialized vertex arrays. Per
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applied to the top matrix on the st
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OpenGL State Variables The followin
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GL_FOG_START Linear fog start fog 0
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GL_TEXTURE_WRAP_x Texture wrap mode
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GL_DOMAIN 1D domain endpoints ⎯
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Appendix C OpenGL and Window System
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glFinish(), glXWaitGL() doesn’t r
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Use aglQueryVersion() to determine
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AGLDrawable aglGetCurrentDrawable (
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A shortcut for using OS/2 logical f
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directly. CreateDIBitmap() creates
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Appendix D Basics of GLUT: The Open
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depending upon whether the mouse ha
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Appendix E Calculating Normal Vecto
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evaluated at a particular point (x,
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Sometimes, you need to vary this me
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transformations.) After transformat
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As before, the inverses are obtaine
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Appendix G Programming Tips This ap
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computations. If your application r
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Appendix H OpenGL Invariance OpenGL
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Appendix I Color Plates This append
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Plate 4 The scene drawn with flat
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Plate 7 The scene drawn with one of
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. Plate 10 Teapots drawn with jitte
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Plate 14 Gray teapots drawn with di
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. Plate 18 Lighted, green teapots d
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Plate 21 An environment−mapped ob
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Plate 23 A magnification of the pre
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Plate 27 Sophisticated use of textu
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Plate 31 Another scene from a diffe
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itplane A rectangular array of bits
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decal A method of calculating color
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gamma correction A function applied
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A source of illumination which has
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A point, a line, a polygon, a bitma
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The 4×4 matrix that transforms tex
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Index
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