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+ * Unpublished-- rights reserved under the copyright laws of the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