GPGPU - używając renderowania poza ekranem (ang. offscreen rendering): nie wysyła danych do bufora ramki[3] (ang. the frame buffer) ale do innej części pamięci karty graficznej (ang. the offscreen buffer)[4]
nie jest biblioteką lecz specyfikacją (API). Nie jest związane ze sprzętem i dzięki temu jest wieloplatformowe, uniwersalne i abstrakcyjne. Nie posiada kodu źródłowego
działa w architekturze klient-serwer
Nie ma okien, menu, procedur obsługi wejścia, czy inneych rodzajów interakcji
język programowania: C, C++, C#, Ada, Java, JavaScript, Python, Ruby, PHP, Lua, R, Perl, OCaml, Common Lisp, Clojure, Fortran, D i wiele innych
środowiska (konsola / IDE)
platforma (OpenGL / OpenGL ES)
wersja OpenGL ( Core-profile vs Tryb natychmiastowy (Immediate mode)[8] :
legacy = 1 lub 2 . Może używać GLUT
modern = czyli 3 lub 4 (GLSL). Nie można korzystać z GLUT, ale zastęþuje go i rozszerza GLFW. Do rysowania i wyświetlania grafiki trzeba używać shaderów [9]
biblioteki podstawowe i ich wersje (Gl, Glu , GLew, ...)
Ponieważ prawie dowolnie można łączyć powyższe cechy (9) liczba możliwych kombinacji jest bardzo duża, dlatego prawie każdy poradnik, program musimy zmodyfikować do naszych warunków.
Dostęp do GPU:
z poziomu X-window: DRI -> GPU (np. Mesa 3D)
z poziomu konsoli bez X-window: DRI -> GPU (np. DirectFB[10])
Sprawdzamy instalację za pomocą konsolowego programu glxinfo (Mesa) [12][13]
glxinfo
lub
glxinfo | more
lub
glxinfo > gl.txt
otrzymujemy:
name of display: :0
display: :0 screen: 0
direct rendering: Yes
server glx vendor string: NVIDIA Corporation
server glx version string: 1.4
server glx extensions:
GLX_ARB_create_context, GLX_ARB_create_context_profile,
GLX_ARB_create_context_robustness, GLX_ARB_fbconfig_float,
GLX_ARB_multisample, GLX_EXT_buffer_age,
GLX_EXT_create_context_es2_profile, GLX_EXT_create_context_es_profile,
GLX_EXT_framebuffer_sRGB, GLX_EXT_swap_control, GLX_EXT_swap_control_tear,
GLX_EXT_texture_from_pixmap, GLX_EXT_visual_info, GLX_EXT_visual_rating,
GLX_NV_float_buffer, GLX_NV_multisample_coverage, GLX_SGIX_fbconfig,
GLX_SGIX_pbuffer, GLX_SGI_swap_control, GLX_SGI_video_sync
client glx vendor string: NVIDIA Corporation
client glx version string: 1.4
client glx extensions:
...
glxinfo | grep "OpenGL version"
przykładowy wynik:
OpenGL version string: 3.0 Mesa 10.3.2
lub:
sudo /usr/lib/nux/unity_support_test -p -f
Przykładowy wynik:
OpenGL vendor string: NVIDIA Corporation
OpenGL renderer string: GeForce GTX 770/PCIe/SSE2
OpenGL version string: 4.3.0 NVIDIA 319.32
Not software rendered: yes
Not blacklisted: yes
GLX fbconfig: yes
GLX texture from pixmap: yes
GL npot or rect textures: yes
GL vertex program: yes
GL fragment program: yes
GL vertex buffer object: yes
GL framebuffer object: yes
GL version is 1.4+: yes
Unity 3D supported: yes
glxinfo | grep 'shading language version string'
Przykładowy wynik:
OpenGL core profile shading language version string: 4.60 NVIDIA
OpenGL shading language version string: 4.60 NVIDIA
OpenGL ES profile shading language version string: OpenGL ES GLSL ES 3.20
Spróbujmy skompilować przeglądarkę dla programistów w Ubuntu używając komendy:
gcc v.c -lm -lGLU -lglut -Wall
Otrzymamy:
v.c: In function ‘readPPM’:
v.c:67:13: warning: variable ‘j’ set but not used [-Wunused-but-set-variable]
int j ;
^
/usr/bin/ld: /tmp/cc2PsYvI.o: undefined reference to symbol 'glDrawPixels'
/usr/lib/nvidia-319/libGL.so.1: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status
Błąd. Kompilator nie widzi definicji procedury glDrawPixels. W Ubuntu problem rozwiązuje dodanie biblioteki GL:
gcc v.c -lm -lGL -lGLU -lglut -Wall
v.c: In function ‘readPPM’:
v.c:67:13: warning: variable ‘j’ set but not used [-Wunused-but-set-variable]
int j ;
^
Jest to niskopoziomowa biblioteka zawierająca procedury do rysowania linii, koloru tła itp.
Otrzymujemy dostęp do OpenGL-1.1. Na więcej potrzebujemy rozszerzeń, np. za pomocą biblioteki GLEW[34]
Podział wg zależności od systemu operacyjnego ( OS )[37]
zależne od OS
bezpośredni ( rendering contexts and pixel formats )
direct rendering from OpenGl application to OpenGl DRIdriver
from framebuffer application to Direct Rendering Manager (DRM)
biblioteki
GLX (ang. OpenGL Extension to the X Window System) – interfejs łączący OpenGL z X Window System i zapewniający działającym w oknach X Window System dostęp do funkcji OpenGL
Direct Rendering Manager(DRM) – komponent Direct Rendering Infrastructure (DRI), czyli systemu sprzętowej akceleracji grafiki pod Linuksa. DRM odpowiada za bezpieczeństwo oraz zarządzaniem zasobami.
DRM składa się z dwóch modułów jądra systemu operacyjnego. Jednego wspólnego dla wszystkich kart graficznych, oraz sterowników właściwych dla konkretnego urządzenia. Obydwa te moduły pozwalają klientowi serwera X, na bezpośredni dostęp do urządzenia (z pominięciem serwera X).
/*http://www.glfw.org/documentation.htmlgcc g.c -lGL -lGLU -lglut -lglfw./a.out*/#include<GLFW/glfw3.h>intmain(void){GLFWwindow*window;/* Initialize the library */if(!glfwInit())return-1;/* Create a windowed mode window and its OpenGL context */window=glfwCreateWindow(640,480,"Hello World",NULL,NULL);if(!window){glfwTerminate();return-1;}/* Make the window's context current */glfwMakeContextCurrent(window);/* Loop until the user closes the window */while(!glfwWindowShouldClose(window)){/* Render here */glClear(GL_COLOR_BUFFER_BIT);/* Swap front and back buffers */glfwSwapBuffers(window);/* Poll for and process events */glfwPollEvents();}glfwTerminate();return0;}
GLEW = OpenGL Extension Wrangler Library (ang.) jest to programistyczna biblioteka międzyplatformowa, pomagająca w odpytywaniu i ładowaniu rozszerzeń OpenGL. GLEW dostarcza efektywne mechanizmy do określania w czasie uruchamiania programu dostępnych rozszerzeń na danej platformie. Wszystkie rozszerzenia OpenGL są wylistowane w jednym pliku nagłówkowym, który z kolei jest maszynowo generowany na podstawie oficjalnej listy rozszerzeń.
GLEW zawiera dodatkowe programy konsolowe, np.: glewinfo
glewinfo>i.txt
W pliku i.txt jest informacja:
---------------------------
GLEW Extension Info
---------------------------
GLEW version 1.8.0
Reporting capabilities of display :0, visual 0x2b
Running on a GeForce GTX 770/PCIe/SSE2 from NVIDIA Corporation
OpenGL version 4.3.0 NVIDIA 319.60 is supported
Następnie jest lista rozszerzeń i informacja o dostępności (OK/MISSING).
GLM[44] to biblioteka matematyczna C++ (i zastępująca stałe funkcje potokowe OpenGL) dla oprogramowania 3D opartego na specyfikacji OpenGL Shading Language (GLSL).
//gcc c.c -lGLEW -lGL -lGLU -lglut //./a.out#include<stdio.h>#include<GL/glew.h>#include<GL/glut.h>#include<GL/gl.h>#include<GL/glu.h>voidmain(intargc,char**argv){glutInit(&argc,argv);glewInit();if(GL_VERSION_4_0)printf("OpenGL 4.0 is supported\n");}
Konsolowy program korzystający z bibliotek GL, GLU, GLUT i GLEW. Tworzy okno wypełnione czerwonym kolorem oraz sprawdza wersję biblioteki GLEW
/*gcc g.c -lGLEW -lGL -lGLU -lglut ./a.outhttp://www.linuxforu.com/2013/04/graphics-programming-in-linux/Graphics Programming in Linux By Rajnish-Singh on April 1, 2013 in Developers, Features, Overview · 3 Commentshttp://www.opengl.org/sdk/libs/GLEW/call glewInit(); once you've obtained a OpenGL context in your program.*/#include<stdio.h>#include<GL/glew.h> // glew before gl #include<GL/gl.h>#include<GL/glu.h>#include<GL/glut.h>voiddisplay(){glClearColor(1,0,0,0);glClear(GL_COLOR_BUFFER_BIT);glFlush();}voidmain(intargc,char**argv){glutInit(&argc,argv);glutInitWindowPosition(100,100);glutInitWindowSize(500,500);glutCreateWindow("Hello World");GLenumerr=glewInit();if(GLEW_OK!=err)fprintf(stderr,"Error: %s\n",glewGetErrorString(err));/* Problem: glewInit failed, something is seriously wrong. */elsefprintf(stdout,"Status: Using GLEW %s\n",glewGetString(GLEW_VERSION));glutDisplayFunc(display);glutMainLoop();}
/*gcc g.c -lGLEW -lGL -lGLU -lglut ./a.outhttp://www.linuxforu.com/2013/04/graphics-programming-in-linux/Graphics Programming in Linux By Rajnish-Singh on April 1, 2013 in Developers, Features, Overview · 3 Commentshttp://www.opengl.org/sdk/libs/GLEW/call glewInit(); once you've obtained a OpenGL context in your program.http://steps3d.narod.ru/tutorials/glew-tutorial.html*/#include<stdio.h>#include<GL/glew.h> // glew before gl #include<GL/gl.h>#include<GL/glu.h>#include<GL/glut.h>voiddisplay(){glClearColor(1,0,0,0);glClear(GL_COLOR_BUFFER_BIT);glFlush();}intmain(intargc,char**argv){glutInit(&argc,argv);glutInitWindowPosition(100,100);glutInitWindowSize(500,500);glutCreateWindow("Hello World");GLenumerr=glewInit();if(GLEW_OK!=err){fprintf(stderr,"Error: %s\n",glewGetErrorString(err));/* Problem: glewInit failed, something is seriously wrong. */return1;}fprintf(stdout,"Status: Using GLEW %s\n",glewGetString(GLEW_VERSION));// checking for extensions if(!GLEW_ARB_shading_language_100){printf("GL_ARB_shading_language_100 NOT supported.\n");return2;}printf("GL_ARB_shading_language_100 is supported.\n");if(!GLEW_ARB_shader_objects){printf("GL_ARB_shader_objects NOT supported");return3;}printf("GL_ARB_shader_objects is supported");if(!GLEW_ARB_vertex_shader||!GLEW_ARB_fragment_shader){printf("No GLSL support\n");exit(4);}printf(" GLSL is supported\n");glutDisplayFunc(display);glutMainLoop();}
dane punktu nad którym znajduje się mysz (patrz procedura Motion, można to zmienić !!!)
Program służy do analizy plików graficznych.
/* * image.c * * read in a PPM or PGM binary image and display it, full size Based on code by : Dr. Lori L. Scarlatos Stony Brook University http://ms.cc.sunysb.edu/~lscarlatos/ "I do not have a license for image.c; it was created as an example for my students. Please feel free to use it. Best regards, Lori"Warning: This article describes legacy OpenGL APIs that have been removed from core OpenGL 3.1 and above (they are only deprecated in OpenGL 3.0). It is recommended that you not use this functionality in your programs.Fixed Function Pipeline* ----------------------------* it does not opens asci versions of these files * examples files : * http://people.sc.fsu.edu/~jburkardt/data/data.htmlhttp://web.eecs.umich.edu/~sugih/courses/eecs487/glut-howto/sample.c // gcc v.c -lm -lGLU -lglut -Wall // ? windows gcc v.c -lm -lglut -lGL -lGLU -Wall // ubuntu ./a.out 5.pgm *//*locate glut.h/usr/include/GL/freeglut.h/usr/include/GL/glut.h#ifdef FREEGLUT#include <GL/freeglut.h>#else#include <GL/glut.h>#endif*///#include <Windows.h>#include<GL/gl.h>#include<GL/glu.h>//#include <GL/glut.h> // oryginal glut #include<GL/freeglut.h> // freeglut #include<stdio.h>#include<string.h>#include<stdlib.h>#include<math.h> /* fabs*///#include <malloc.h>/* Global variables */#define MAXLINE 80 /* maximum length of a line of text *//*3.2 ConventionsIn developing the freeglut library, we have taken careful steps to ensure consistency in function operation across the board, in such a manner as to maintain compatibility with GLUT's behavior whenever possible. In this section some of the important conventions of FreeGLUT, and their compatibility with GLUT, are made explicit.3.2.1 Window placement and sizeThere is considerable confusion about the "right thing to do" concerning window size and position. GLUT itself is not consistent between Windows and UNIX/X11; since platform independence is a virtue for freeglut, we decided to break with GLUT's behaviour. Under UNIX/X11, it is apparently not possible to get the window border sizes in order to subtract them off the window's initial position until some time after the window has been created. Therefore we decided on the following behavior, both under Windows and under UNIX/X11:When you create a window with position (x,y) and size (w,h), the upper left hand corner of the outside of the window (the non-client area) is at (x,y) and the size of the drawable (client) area is (w,h). The coordinates taken by glutInitPosition and glutPositionWindow, as well as the coordinates provided by FreeGLUT when it calls the glutPositionFunc callback, specify the top-left of the non-client area of the window.When you query the size and position of the window using glutGet, FreeGLUT will return the size of the drawable area--the (w,h) that you specified when you created the window--and the coordinates of the upper left hand corner of the drawable (client) area--which is NOT the (x,y) position of the window you specified when you created it.*/GLintImageWidth,ImageHeight;/* size of the Image in pixels */GLintWindowWidth,WindowHeight;/* size of the window in pixels */GLintMaxScreenWidth,MaxScreenHeight;/* size of the screen in pixels */GLubyte*Picture;/* Array of colors (GLubyte) */intsize;// mouse position as a global variables //static float mx=0.0f,my=0.0f ;intiX,iY;// intcenterX=200,centerY=200;GLintiYmax,iXmax;// mouse coordinate inside image unsignedcharpixel[3];// change it manually !!!!!constdoubleZyMin=-1.0;constdoubleZxMin=-2.0;constdoublePixelHeight=0.0020010005002501;constdoublePixelWidth=0.0020010005002501;intfiletype;enum{P2,P3,P5,P6};/* possible file types *//* gives position of point (iX,iY) in 1D array ; uses also global variables */unsignedintf(unsignedint_iX,unsignedint_iY){return(_iX+(iYmax-_iY-1)*iXmax);}/* * Read from a PPM or PGM (binary) file * Output is a array of GLubyte */voidreadPPM(char*filename,GLubyte**pic){FILE*fp;charline[MAXLINE];inti,rowsize;// int size; // moved to global var intj;GLubyte*ptr;/* Read in file type */fp=fopen(filename,"r");/* in Unix rb = r */if(fp==NULL){perror(" perror : ");printf("Error from fopen : I can't open %s file' ! ",filename);exit(1);}elseprintf("File %s has been opened !\n",filename);/* Each file starts with aa two-byte magic number (in ASCII) that explains : * - the type of file it is (PBM, PGM, and PPM) * - its encoding (ASCII or binary). * The magic number is a capital P followed by a single digit number. */fgets(line,MAXLINE,fp);/* 1st line : Magic Number */switch(line[1]){case'2':filetype=P2;printf("This is PGM text file (P2), but now I do not have procedure for opening it \n");break;case'3':filetype=P3;printf("This is PPM text file (P3), but now I do not have procedure for opening it !\n");break;case'5':filetype=P5;printf("This is PGM binary file (P5) and I can open it !\n");break;case'6':filetype=P6;printf("This is PPM binary file (P6) and I can open it !\n");break;default:printf("Error from readPPM : need binary PPM or binary PGM file as input!\n");exit(1);}/* if this is a comment, read next line. Maybe in binary files there is no comment ?*//* there maybe more then one line of comment */fgets(line,MAXLINE,fp);while(line[0]=='#'){printf(" comment = %s \n",line);/* 2nd or more line starting with # = comment, print it */fgets(line,MAXLINE,fp);// read next line }/* Read in width and height, & allocate space *//* these 2 numbers should be in one line with space between them *//* 3nd line: width and height */sscanf(line,"%d %d",&ImageWidth,&ImageHeight);printf("iWidth = %d\n",ImageWidth);printf("iHeight = %d\n",ImageHeight);iXmax=ImageWidth-1;iYmax=ImageHeight-1;if(filetype==P5){size=ImageHeight*ImageWidth;/* greymap: 1 byte per pixel */rowsize=ImageWidth;}else/* filetype == P6 */{size=ImageHeight*ImageWidth*3;/* pixmap: 3 bytes per pixel */rowsize=ImageWidth*3;}*pic=(GLubyte*)malloc(size);/* create dynamic array *//* Read in maximum value (ignore) */fgets(line,MAXLINE,fp);/* next line *//* */if(filetype==P5||filetype==P6){/* Read in the pixel array row-by-row: 1st row = top scanline */ptr=*pic+(ImageHeight-1)*rowsize;for(i=ImageHeight;i>0;i--){/* For binary File I/O you use fread and fwrite */j=fread((void*)ptr,1,rowsize,fp);ptr-=rowsize;}if(j)printf("File %s has been read !\n",filename);elseprintf(" j Error from readPPM procedure : I can't read %d file !.\n",j);}elseprintf("Error from readPPM procedure : I can't read %s file !. It should be P5 or P6 file !\n",filename);fclose(fp);printf("File %s has been closed !\n",filename);}/* Draw the picture on the screen */voidDraw(void){/* black background of GLUT window */glClearColor(0.0f,0.0f,0.0f,1.0f);// Clear the background of our window to blackglClear(GL_COLOR_BUFFER_BIT);//Clear the colour buffer (more buffers later on)glLoadIdentity();// Load the Identity Matrix to reset our drawing locationsglFlush();// Flush the OpenGL buffers to the window// left lower corner of displayed image glRasterPos2i(-1,-1);// By default, OpenGL assumes a system running from -1 to 1, switch(filetype){caseP5:/* greymap: use as illumination values */glDrawPixels(ImageWidth,ImageHeight,GL_LUMINANCE,GL_UNSIGNED_BYTE,Picture);printf("P5 Image has been drawn !\n");break;caseP6:glDrawPixels(ImageWidth,ImageHeight,GL_RGB,GL_UNSIGNED_BYTE,Picture);printf("P6 Image has been drawn !\n");break;default:printf("Error from Draw procedure : There is no image to draw !\n");}}// Detecting Mouse Clicks// x and y specify the location (in window-relative coordinates) of the mouse when// the event occurredvoidMouseClicks(intbutton,intstate,intx,inty){switch(button)caseGLUT_LEFT_BUTTON:if(state==GLUT_DOWN)// do somethingcaseGLUT_RIGHT_BUTTON:;// etc., etc.}// mouse motion //The x and y callback parameters // indicate the mouse location // in window relative coordinates//// x, y –> coordinates of the mouse relative to upper left corner of window// setting the mouse position to be relative to the mouse// position inside the window//voidPassiveMouseMotion(intx,inty){//double Zx,Zy;//double Ux; //int index;//GLubyte Gray;// put your code here ???? iX=x;/* invert y axis */iY=WindowHeight-y-1;//+ (glutGet(GLUT_WINDOW_HEIGHT) - ImageHeight); ///glutGet(GLUT_WINDOW_HEIGHT) - y; // ????/* output : prints to console */if((filetype==P5||filetype==P6)&&-1<iX&&iX<ImageWidth&&iY<ImageHeight)// && iY<ImageHeight{glReadPixels(iX,iY,1,1,GL_RGB,GL_UNSIGNED_BYTE,pixel);// pixel coordinates of the mouse relative to upper left corner of windowprintf(" pixel iX=%3d / %d ; iY=%3d color = %d \n",iX,MaxScreenWidth,iY,pixel[1]);}}staticvoidKey(unsignedcharkey,intx,inty){switch(key){case27:{glutLeaveFullScreen();break;}/* esc */case'f':{glutFullScreen();break;}case'q':{printf("Key preseed and exit \n");exit(1);}case'Q':{printf("Key preseed and exit \n");exit(1);}case't':{glutFullScreenToggle();break;}// GLUT does not include the glutLeaveFullScreen and glutFullScreenToggle functions from freeglut default:return;}}/* Resize the picture ; OpenGL calls this function whenever the window is resized Called when window is resized, also when window is first created, before the first call to display().*/voidReshape(GLintw,GLinth){/* save new screen dimensions */WindowWidth=w;WindowHeight=h;/* the viewport is the rectangular region of the window where the image is drawn */// Viewport : A rectangular region in the screen for display (in screen coordinate system) glViewport(0,0,ImageWidth-1,ImageHeight-1);// glViewport( 0.f, 0.f, SCREEN_WIDTH, SCREEN_HEIGHT );glMatrixMode(GL_PROJECTION);glLoadIdentity();// Define a world window : A rectangular region in the world that is to be displayed (in world coordinate system)// By default, OpenGL assumes a system running from -1 to 1, gluOrtho2D(-1,1,-1,1);// An orthographic projection is basically a 3D projection that does not have perspectiveglMatrixMode(GL_MODELVIEW);glLoadIdentity();}/* Initialization: create window glutInitWindowSize(600, 600);*/voidMyInit(intargc,char*argv[]){charfilename[MAXLINE];/* Read in the file (allocates space for Picture) */if(argc<2){printf("Enter the name of a binary PPM or PGM file: ");scanf("%s",filename);readPPM((char*)filename,&Picture);}else{readPPM(argv[1],&Picture);}glutInit(&argc,argv);MaxScreenWidth=glutGet(GLUT_SCREEN_WIDTH);MaxScreenHeight=glutGet(GLUT_SCREEN_HEIGHT);glutInitWindowPosition(-1,1);// upper left cornerglutInitWindowSize(MaxScreenWidth,MaxScreenHeight);// full screen of my monitorglutInitDisplayMode(GLUT_RGB|GLUT_SINGLE);if(glutCreateWindow("OpenGl binary pgm/ppm Image viewer ")==GL_FALSE){printf("Error from MyInit , glutCreateWindow\n");exit(1);}}/* ------------------ Main program ---------------------------------------*/intmain(intargc,char**argv){MyInit(argc,argv);glutPassiveMotionFunc(PassiveMouseMotion);// mouse move with no key pressed glutReshapeFunc(Reshape);// move or resize of screen window glutDisplayFunc(Draw);// glutKeyboardFunc(Key);//glutMainLoop();return0;}
Q: Czego lepiej używać, wymiarów typu 1.0f, -2,0f, czy wartości w pixelach 100, 550 - przy rysowaniu?
A: "Używaj tego co Ci wygodniej. Większość instrukcji operujących na wierzchołkach ma wersje dla liczb całkowitych - te z przedrostkiem i, jak i zmiennoprzecinkowych - te z przedrostkiem f(float) lub d(double)).
np: glVertex2i(x,y), glVertex2f(x,y), glVertex3d(x,y,z) itd." [49]
Q: Gdzie definiujemy viewport?
A: W 2 miejscach:
w inicjalizacji, wtedy ma taki sam rozmiar jak całe okno
w funkcji zmieniającej rozmiar okna (glutReshapeFunc)
wielkość fragmentu okna ekranu gdzie jest wyświetlany obraz (ang. viewport) [50][51]
Współrzędne są liczbami całkowitymi:
glutInitWindowSize(2560, 1440); // screen width, screen height in poixels
glViewport(50, 50, 350, 250); // viewport left down and upper right corners in window coordinate
