/**************************************************************************** Copyright 1995 by Silicon Graphics Incorporated, Mountain View, California. All Rights Reserved Permission to use, copy, modify, and distribute this software and its documentation for any purpose and without fee is hereby granted, provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation, and that the name of Silicon Graphics not be used in advertising or publicity pertaining to distribution of the software without specific, written prior permission. SILICON GRAPHICS DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL SILICON GRAPHICS BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. ****************************************************************************/ /* * Derived from code written by Kurt Akeley, November 1992 * * Uses PolygonOffset to draw hidden-line images. PolygonOffset * shifts the z values of polygons an amount that is * proportional to their slope in screen z. This keeps * the lines, which are drawn without displacement, from * interacting with their respective polygons, and * thus eliminates line dropouts. * * The left image shows an ordinary antialiased wireframe image. * The center image shows an antialiased hidden-line image without * PolygonOffset. * The right image shows an antialiased hidden-line image using * PolygonOffset to reduce artifacts. * * Drag with a mouse button pressed to rotate the models. * Press the escape key to exit. */ /* * Modified for OpenGL 1.1 glPolygonOffset() conventions */ #include <GL/glx.h> #include <X11/keysym.h> #include <stdlib.h> #include <stdio.h> #include <string.h> #undef GL_EXT_polygon_offset /* use GL 1.1 version instead of extension */ #ifndef EXIT_FAILURE # define EXIT_FAILURE 1 #endif #ifndef EXIT_SUCCESS # define EXIT_SUCCESS 0 #endif #define MAXQUAD 6 typedef float Vertex[3]; typedef Vertex Quad[4]; /* data to define the six faces of a unit cube */ Quad quads[MAXQUAD] = { { {0,0,0}, {0,0,1}, {0,1,1}, {0,1,0} }, /* x = 0 */ { {0,0,0}, {1,0,0}, {1,0,1}, {0,0,1} }, /* y = 0 */ { {0,0,0}, {1,0,0}, {1,1,0}, {0,1,0} }, /* z = 0 */ { {1,0,0}, {1,0,1}, {1,1,1}, {1,1,0} }, /* x = 1 */ { {0,1,0}, {1,1,0}, {1,1,1}, {0,1,1} }, /* y = 1 */ { {0,0,1}, {1,0,1}, {1,1,1}, {0,1,1} } /* z = 1 */ }; #define WIREFRAME 0 #define HIDDEN_LINE 1 static void error(const char* prog, const char* msg); static void cubes(int mx, int my, int mode); static void fill(Quad quad); static void outline(Quad quad); static void draw_hidden(Quad quad, int mode, int face); static void process_input(Display *dpy, Window win); static int query_extension(char* extName); static int attributeList[] = { GLX_RGBA, GLX_RED_SIZE, 1, GLX_GREEN_SIZE, 1, GLX_BLUE_SIZE, 1, GLX_DOUBLEBUFFER, GLX_DEPTH_SIZE, 1, None }; static int dimension = 3; int main(int argc, char** argv) { Display *dpy; XVisualInfo *vi; XSetWindowAttributes swa; Window win; GLXContext cx; GLint z; dpy = XOpenDisplay(0); if (!dpy) error(argv[0], "can't open display"); vi = glXChooseVisual(dpy, DefaultScreen(dpy), attributeList); if (!vi) error(argv[0], "no suitable visual"); cx = glXCreateContext(dpy, vi, 0, GL_TRUE); swa.colormap = XCreateColormap(dpy, RootWindow(dpy, vi->screen), vi->visual, AllocNone); swa.border_pixel = 0; swa.event_mask = ExposureMask | StructureNotifyMask | KeyPressMask | ButtonPressMask | ButtonMotionMask; win = XCreateWindow(dpy, RootWindow(dpy, vi->screen), 0, 0, 900, 300, 0, vi->depth, InputOutput, vi->visual, CWBorderPixel|CWColormap|CWEventMask, &swa); XStoreName(dpy, win, "hiddenline"); XMapWindow(dpy, win); glXMakeCurrent(dpy, win, cx); /* check for the polygon offset extension */ #ifndef GL_VERSION_1_1 if (!query_extension("GL_EXT_polygon_offset")) error(argv[0], "polygon_offset extension is not available"); #else (void) query_extension; #endif /* set up viewing parameters */ glMatrixMode(GL_PROJECTION); glFrustum(-1, 1, -1, 1, 6, 20); glMatrixMode(GL_MODELVIEW); glTranslatef(0, 0, -15); /* set other relevant state information */ glEnable(GL_DEPTH_TEST); glGetIntegerv(GL_DEPTH_BITS, &z); printf("GL_DEPTH_BITS = %d\n", z); #ifdef GL_EXT_polygon_offset printf("using 1.0 offset extension\n"); glPolygonOffsetEXT( 1.0, 0.00001 ); #else printf("using 1.1 offset\n"); glPolygonOffset( 1.0, 0.5 ); #endif glShadeModel( GL_FLAT ); glDisable( GL_DITHER ); /* process events until the user presses ESC */ while (1) process_input(dpy, win); return 0; } static void draw_scene(int mx, int my) { glClearColor(0.25, 0.25, 0.25, 0); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glPushMatrix(); glTranslatef(-1.7, 0.0, 0.0); cubes(mx, my, WIREFRAME); glPopMatrix(); glPushMatrix(); cubes(mx, my, HIDDEN_LINE); glPopMatrix(); glPushMatrix(); glTranslatef(1.7, 0.0, 0.0); #ifdef GL_EXT_polygon_offset glEnable(GL_POLYGON_OFFSET_EXT); #else glEnable(GL_POLYGON_OFFSET_FILL); #endif cubes(mx, my, HIDDEN_LINE); #ifdef GL_EXT_polygon_offset glDisable(GL_POLYGON_OFFSET_EXT); #else glDisable(GL_POLYGON_OFFSET_FILL); #endif glPopMatrix(); } static void cubes(int mx, int my, int mode) { int x, y, z, i; /* track the mouse */ glRotatef(mx / 2.0, 0, 1, 0); glRotatef(my / 2.0, 1, 0, 0); /* draw the lines as hidden polygons */ glTranslatef(-0.5, -0.5, -0.5); glScalef(1.0/dimension, 1.0/dimension, 1.0/dimension); for (z = 0; z < dimension; z++) { for (y = 0; y < dimension; y++) { for (x = 0; x < dimension; x++) { glPushMatrix(); glTranslatef(x, y, z); glScalef(0.8, 0.8, 0.8); for (i = 0; i < MAXQUAD; i++) draw_hidden(quads[i], mode, i); glPopMatrix(); } } } } static void fill(Quad quad) { /* draw a filled polygon */ glBegin(GL_QUADS); glVertex3fv(quad[0]); glVertex3fv(quad[1]); glVertex3fv(quad[2]); glVertex3fv(quad[3]); glEnd(); } static void outline(Quad quad) { /* draw an outlined polygon */ glBegin(GL_LINE_LOOP); glVertex3fv(quad[0]); glVertex3fv(quad[1]); glVertex3fv(quad[2]); glVertex3fv(quad[3]); glEnd(); } static void draw_hidden(Quad quad, int mode, int face) { static const GLfloat colors[3][3] = { {0.5, 0.5, 0.0}, {0.8, 0.5, 0.0}, {0.0, 0.5, 0.8} }; if (mode == HIDDEN_LINE) { glColor3fv(colors[face % 3]); fill(quad); } /* draw the outline using white */ glColor3f(1, 1, 1); outline(quad); } static void process_input(Display *dpy, Window win) { XEvent event; static int prevx, prevy; static int deltax = 90, deltay = 40; do { char buf[31]; KeySym keysym; XNextEvent(dpy, &event); switch(event.type) { case Expose: break; case ConfigureNotify: { /* this approach preserves a 1:1 viewport aspect ratio */ int vX, vY, vW, vH; int eW = event.xconfigure.width, eH = event.xconfigure.height; if (eW >= eH) { vX = 0; vY = (eH - eW) >> 1; vW = vH = eW; } else { vX = (eW - eH) >> 1; vY = 0; vW = vH = eH; } glViewport(vX, vY, vW, vH); } break; case KeyPress: (void) XLookupString(&event.xkey, buf, sizeof(buf), &keysym, NULL); switch (keysym) { case XK_Escape: exit(EXIT_SUCCESS); default: break; } case ButtonPress: prevx = event.xbutton.x; prevy = event.xbutton.y; break; case MotionNotify: deltax += (event.xbutton.x - prevx); prevx = event.xbutton.x; deltay += (event.xbutton.y - prevy); prevy = event.xbutton.y; break; default: break; } } while (XPending(dpy)); draw_scene(deltax, deltay); glXSwapBuffers(dpy, win); } static void error(const char *prog, const char *msg) { fprintf(stderr, "%s: %s\n", prog, msg); exit(EXIT_FAILURE); } static int query_extension(char* extName) { char *p = (char *) glGetString(GL_EXTENSIONS); char *end = p + strlen(p); while (p < end) { int n = strcspn(p, " "); if ((strlen(extName) == n) && (strncmp(extName, p, n) == 0)) return GL_TRUE; p += (n + 1); } return GL_FALSE; }