157 lines
3.6 KiB
C
157 lines
3.6 KiB
C
/*
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* Copyright (c) 1991, 1992, 1993 Silicon Graphics, Inc.
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*
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* Permission to use, copy, modify, distribute, and sell this software and
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* its documentation for any purpose is hereby granted without fee, provided
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* that (i) the above copyright notices and this permission notice appear in
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* all copies of the software and related documentation, and (ii) the name of
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* Silicon Graphics may not be used in any advertising or
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* publicity relating to the software without the specific, prior written
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* permission of Silicon Graphics.
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*
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* THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF
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* ANY KIND,
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* EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY
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* WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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*
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* IN NO EVENT SHALL SILICON GRAPHICS BE LIABLE FOR
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* ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,
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* OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
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* WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF
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* LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
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* OF THIS SOFTWARE.
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*/
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#define GL_GLEXT_PROTOTYPES
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#include <math.h>
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include <GL/glut.h>
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GLenum doubleBuffer;
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static void Init(void)
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{
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fprintf(stderr, "GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER));
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fprintf(stderr, "GL_VERSION = %s\n", (char *) glGetString(GL_VERSION));
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fprintf(stderr, "GL_VENDOR = %s\n", (char *) glGetString(GL_VENDOR));
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glClearColor(0.0, 0.0, 1.0, 0.0);
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}
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static void Reshape(int width, int height)
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{
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glViewport(0, 0, (GLint)width, (GLint)height);
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glMatrixMode(GL_PROJECTION);
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glLoadIdentity();
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glOrtho(-1.0, 1.0, -1.0, 1.0, 0, 100.0);
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glMatrixMode(GL_MODELVIEW);
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}
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static void Key(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(1);
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default:
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return;
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}
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glutPostRedisplay();
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}
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static float
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expected(float z, float size, const float atten[3])
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{
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float dist = fabs(z);
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const GLfloat q = atten[0] + dist * (atten[1] + dist * atten[2]);
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const GLfloat a = sqrt(1.0 / q);
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return size * a;
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}
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static void Draw(void)
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{
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static GLfloat atten[3] = { 0.0, 0.1, .01 };
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float size = 40.0;
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int i;
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glClear(GL_COLOR_BUFFER_BIT);
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glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
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glPointSize(size);
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glPointParameterfvARB(GL_POINT_DISTANCE_ATTENUATION_ARB, atten);
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glColor3f(1,0,0);
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printf("Expected point sizes:\n");
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glBegin(GL_POINTS);
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for (i = 0; i < 5; i++) {
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float x = -0.8 + i * 0.4;
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float z = -i * 20 - 10;
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glVertex3f( x, 0.0, z);
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printf(" %f\n", expected(z, size, atten));
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}
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glEnd();
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glFlush();
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if (doubleBuffer) {
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glutSwapBuffers();
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}
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}
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static GLenum Args(int argc, char **argv)
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{
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GLint i;
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doubleBuffer = GL_FALSE;
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for (i = 1; i < argc; i++) {
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if (strcmp(argv[i], "-sb") == 0) {
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doubleBuffer = GL_FALSE;
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} else if (strcmp(argv[i], "-db") == 0) {
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doubleBuffer = GL_TRUE;
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} else {
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fprintf(stderr, "%s (Bad option).\n", argv[i]);
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return GL_FALSE;
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}
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}
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return GL_TRUE;
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}
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int main(int argc, char **argv)
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{
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GLenum type;
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glutInit(&argc, argv);
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if (Args(argc, argv) == GL_FALSE) {
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exit(1);
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}
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glutInitWindowPosition(0, 0); glutInitWindowSize( 250, 250);
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type = GLUT_RGB;
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type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE;
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glutInitDisplayMode(type);
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if (glutCreateWindow(argv[0]) == GL_FALSE) {
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exit(1);
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}
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Init();
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glutReshapeFunc(Reshape);
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glutKeyboardFunc(Key);
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glutDisplayFunc(Draw);
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glutMainLoop();
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return 0;
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}
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