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Diffstat (limited to 'progs/trivial/tri-blend-sub.c')
-rw-r--r-- | progs/trivial/tri-blend-sub.c | 145 |
1 files changed, 145 insertions, 0 deletions
diff --git a/progs/trivial/tri-blend-sub.c b/progs/trivial/tri-blend-sub.c new file mode 100644 index 0000000..d207791 --- /dev/null +++ b/progs/trivial/tri-blend-sub.c @@ -0,0 +1,145 @@ +/* + * 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 + * Unpublished-- rights reserved under the copyright laws of the + * United States.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. + */ + +/* + * alpha.c + * This program draws several overlapping filled polygons + * to demonstrate the effect order has on alpha blending results. + * Use the 't' key to toggle the order of drawing polygons. + */ +#include <GL/glut.h> +#include <stdlib.h> + +static int leftFirst = GL_TRUE; + +/* Initialize alpha blending function. + */ +static void init(void) +{ + glBlendEquation (GL_FUNC_SUBTRACT); + glBlendFunc (GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); + glShadeModel (GL_FLAT); + glClearColor (1.0, 0.0, 0.0, 0.0); +} + +static void drawLeftTriangle(void) +{ + /* draw yellow triangle on LHS of screen */ + + glBegin (GL_TRIANGLES); + glColor4f(1.0, 1.0, 0.0, 0.75); + glVertex3f(0.1, 0.9, 0.0); + glVertex3f(0.1, 0.1, 0.0); + glVertex3f(0.7, 0.5, 0.0); + glEnd(); +} + +static void drawRightTriangle(void) +{ + /* draw cyan triangle on RHS of screen */ + + glEnable (GL_BLEND); + glBegin (GL_TRIANGLES); + glColor4f(0.0, 1.0, 1.0, 0.75); + glVertex3f(0.9, 0.9, 0.0); + glVertex3f(0.3, 0.5, 0.0); + glVertex3f(0.9, 0.1, 0.0); + glEnd(); + glDisable (GL_BLEND); +} + +void display(void) +{ + glClear(GL_COLOR_BUFFER_BIT); + + if (leftFirst) { + drawLeftTriangle(); + drawRightTriangle(); + } + else { + drawRightTriangle(); + drawLeftTriangle(); + } + + glFlush(); +} + +void reshape(int w, int h) +{ + glViewport(0, 0, (GLsizei) w, (GLsizei) h); + glMatrixMode(GL_PROJECTION); + glLoadIdentity(); + if (w <= h) + gluOrtho2D (0.0, 1.0, 0.0, 1.0*(GLfloat)h/(GLfloat)w); + else + gluOrtho2D (0.0, 1.0*(GLfloat)w/(GLfloat)h, 0.0, 1.0); +} + +/* ARGSUSED1 */ +void keyboard(unsigned char key, int x, int y) +{ + switch (key) { + case 't': + case 'T': + leftFirst = !leftFirst; + glutPostRedisplay(); + break; + case 27: /* Escape key */ + exit(0); + break; + default: + break; + } +} + +/* Main Loop + * Open window with initial window size, title bar, + * RGBA display mode, and handle input events. + */ +int main(int argc, char** argv) +{ + glutInit(&argc, argv); + glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB); + glutInitWindowSize (200, 200); + glutCreateWindow (argv[0]); + init(); + glutReshapeFunc (reshape); + glutKeyboardFunc (keyboard); + glutDisplayFunc (display); + glutMainLoop(); + return 0; +} |