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jtg
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progs/redbook/select.c
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progs/redbook/select.c
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/*
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* Copyright (c) 1993-1997, Silicon Graphics, Inc.
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* ALL RIGHTS RESERVED
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* Permission to use, copy, modify, and distribute this software for
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* any purpose and without fee is hereby granted, provided that the above
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* copyright notice appear in all copies and that both the copyright notice
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* and this permission notice appear in supporting documentation, and that
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* the name of Silicon Graphics, Inc. not be used in advertising
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* or publicity pertaining to distribution of the software without specific,
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* written prior permission.
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*
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* THE MATERIAL EMBODIED ON THIS SOFTWARE IS PROVIDED TO YOU "AS-IS"
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* AND WITHOUT WARRANTY OF ANY KIND, EXPRESS, IMPLIED OR OTHERWISE,
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* INCLUDING WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY OR
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* FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL SILICON
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* GRAPHICS, INC. BE LIABLE TO YOU OR ANYONE ELSE FOR ANY DIRECT,
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* SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY
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* KIND, OR ANY DAMAGES WHATSOEVER, INCLUDING WITHOUT LIMITATION,
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* LOSS OF PROFIT, LOSS OF USE, SAVINGS OR REVENUE, OR THE CLAIMS OF
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* THIRD PARTIES, WHETHER OR NOT SILICON GRAPHICS, INC. HAS BEEN
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* ADVISED OF THE POSSIBILITY OF SUCH LOSS, HOWEVER CAUSED AND ON
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* ANY THEORY OF LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE
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* POSSESSION, USE OR PERFORMANCE OF THIS SOFTWARE.
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*
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* US Government Users Restricted Rights
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* Use, duplication, or disclosure by the Government is subject to
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* restrictions set forth in FAR 52.227.19(c)(2) or subparagraph
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* (c)(1)(ii) of the Rights in Technical Data and Computer Software
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* clause at DFARS 252.227-7013 and/or in similar or successor
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* clauses in the FAR or the DOD or NASA FAR Supplement.
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* Unpublished-- rights reserved under the copyright laws of the
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* United States. Contractor/manufacturer is Silicon Graphics,
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* Inc., 2011 N. Shoreline Blvd., Mountain View, CA 94039-7311.
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*
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* OpenGL(R) is a registered trademark of Silicon Graphics, Inc.
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*/
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/*
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* select.c
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* This is an illustration of the selection mode and
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* name stack, which detects whether objects which collide
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* with a viewing volume. First, four triangles and a
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* rectangular box representing a viewing volume are drawn
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* (drawScene routine). The green triangle and yellow
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* triangles appear to lie within the viewing volume, but
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* the red triangle appears to lie outside it. Then the
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* selection mode is entered (selectObjects routine).
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* Drawing to the screen ceases. To see if any collisions
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* occur, the four triangles are called. In this example,
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* the green triangle causes one hit with the name 1, and
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* the yellow triangles cause one hit with the name 3.
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*/
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#include <GL/glut.h>
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#include <stdlib.h>
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#include <stdio.h>
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/* draw a triangle with vertices at (x1, y1), (x2, y2)
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* and (x3, y3) at z units away from the origin.
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*/
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void drawTriangle (GLfloat x1, GLfloat y1, GLfloat x2,
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GLfloat y2, GLfloat x3, GLfloat y3, GLfloat z)
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{
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glBegin (GL_TRIANGLES);
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glVertex3f (x1, y1, z);
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glVertex3f (x2, y2, z);
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glVertex3f (x3, y3, z);
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glEnd ();
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}
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/* draw a rectangular box with these outer x, y, and z values */
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void drawViewVolume (GLfloat x1, GLfloat x2, GLfloat y1,
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GLfloat y2, GLfloat z1, GLfloat z2)
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{
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glColor3f (1.0, 1.0, 1.0);
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glBegin (GL_LINE_LOOP);
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glVertex3f (x1, y1, -z1);
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glVertex3f (x2, y1, -z1);
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glVertex3f (x2, y2, -z1);
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glVertex3f (x1, y2, -z1);
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glEnd ();
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glBegin (GL_LINE_LOOP);
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glVertex3f (x1, y1, -z2);
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glVertex3f (x2, y1, -z2);
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glVertex3f (x2, y2, -z2);
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glVertex3f (x1, y2, -z2);
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glEnd ();
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glBegin (GL_LINES); /* 4 lines */
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glVertex3f (x1, y1, -z1);
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glVertex3f (x1, y1, -z2);
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glVertex3f (x1, y2, -z1);
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glVertex3f (x1, y2, -z2);
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glVertex3f (x2, y1, -z1);
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glVertex3f (x2, y1, -z2);
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glVertex3f (x2, y2, -z1);
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glVertex3f (x2, y2, -z2);
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glEnd ();
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}
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/* drawScene draws 4 triangles and a wire frame
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* which represents the viewing volume.
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*/
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void drawScene (void)
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{
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glMatrixMode (GL_PROJECTION);
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glLoadIdentity ();
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gluPerspective (40.0, 4.0/3.0, 1.0, 100.0);
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glMatrixMode (GL_MODELVIEW);
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glLoadIdentity ();
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gluLookAt (7.5, 7.5, 12.5, 2.5, 2.5, -5.0, 0.0, 1.0, 0.0);
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glColor3f (0.0, 1.0, 0.0); /* green triangle */
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drawTriangle (2.0, 2.0, 3.0, 2.0, 2.5, 3.0, -5.0);
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glColor3f (1.0, 0.0, 0.0); /* red triangle */
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drawTriangle (2.0, 7.0, 3.0, 7.0, 2.5, 8.0, -5.0);
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glColor3f (1.0, 1.0, 0.0); /* yellow triangles */
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drawTriangle (2.0, 2.0, 3.0, 2.0, 2.5, 3.0, 0.0);
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drawTriangle (2.0, 2.0, 3.0, 2.0, 2.5, 3.0, -10.0);
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drawViewVolume (0.0, 5.0, 0.0, 5.0, 0.0, 10.0);
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}
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/* processHits prints out the contents of the selection array
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*/
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void processHits (GLint hits, GLuint buffer[])
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{
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unsigned int i, j;
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GLuint names, *ptr;
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printf ("hits = %d\n", hits);
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ptr = (GLuint *) buffer;
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for (i = 0; i < hits; i++) { /* for each hit */
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names = *ptr;
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printf (" number of names for hit = %d\n", names); ptr++;
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printf(" z1 is %g;", (float) *ptr/0x7fffffff); ptr++;
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printf(" z2 is %g\n", (float) *ptr/0x7fffffff); ptr++;
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printf (" the name is ");
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for (j = 0; j < names; j++) { /* for each name */
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printf ("%d ", *ptr); ptr++;
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}
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printf ("\n");
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}
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}
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/* selectObjects "draws" the triangles in selection mode,
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* assigning names for the triangles. Note that the third
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* and fourth triangles share one name, so that if either
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* or both triangles intersects the viewing/clipping volume,
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* only one hit will be registered.
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*/
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#define BUFSIZE 512
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void selectObjects(void)
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{
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GLuint selectBuf[BUFSIZE];
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GLint hits;
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glSelectBuffer (BUFSIZE, selectBuf);
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(void) glRenderMode (GL_SELECT);
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glInitNames();
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glPushName(0);
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glPushMatrix ();
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glMatrixMode (GL_PROJECTION);
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glLoadIdentity ();
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glOrtho (0.0, 5.0, 0.0, 5.0, 0.0, 10.0);
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glMatrixMode (GL_MODELVIEW);
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glLoadIdentity ();
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glLoadName(1);
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drawTriangle (2.0, 2.0, 3.0, 2.0, 2.5, 3.0, -5.0);
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glLoadName(2);
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drawTriangle (2.0, 7.0, 3.0, 7.0, 2.5, 8.0, -5.0);
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glLoadName(3);
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drawTriangle (2.0, 2.0, 3.0, 2.0, 2.5, 3.0, 0.0);
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drawTriangle (2.0, 2.0, 3.0, 2.0, 2.5, 3.0, -10.0);
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glPopMatrix ();
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glFlush ();
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hits = glRenderMode (GL_RENDER);
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processHits (hits, selectBuf);
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}
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void init (void)
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{
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glEnable(GL_DEPTH_TEST);
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glShadeModel(GL_FLAT);
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}
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void display(void)
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{
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glClearColor (0.0, 0.0, 0.0, 0.0);
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glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
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drawScene ();
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selectObjects ();
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glFlush();
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}
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/* ARGSUSED1 */
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void keyboard(unsigned char key, int x, int y)
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{
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switch (key) {
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case 27:
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exit(0);
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break;
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}
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}
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/* Main Loop */
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int main(int argc, char** argv)
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{
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glutInit(&argc, argv);
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glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
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glutInitWindowSize (200, 200);
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glutInitWindowPosition (100, 100);
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glutCreateWindow (argv[0]);
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init();
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glutDisplayFunc(display);
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glutKeyboardFunc(keyboard);
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glutMainLoop();
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return 0;
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}
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