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/* * Copyright (c) 1993-1999, 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 * Unpublished-- rights reserved under the copyright laws of the * United States.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#include #include /* 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, -1.0); drawTriangle (2.0, 2.0, 3.0, 2.0, 2.5, 3.0, -9.0); 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[]) { unsigned int i, j; GLuint 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, -1.0); drawTriangle (2.0, 2.0, 3.0, 2.0, 2.5, 3.0, -9.0); 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(); } 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; }