forked from KolibriOS/kolibrios
719 lines
16 KiB
HTML
719 lines
16 KiB
HTML
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<HTML
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><HEAD
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><TITLE
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>Using OpenGL With SDL</TITLE
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><META
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NAME="GENERATOR"
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CONTENT="Modular DocBook HTML Stylesheet Version 1.64
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"><LINK
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REL="HOME"
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TITLE="SDL Library Documentation"
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HREF="index.html"><LINK
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REL="UP"
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TITLE="Graphics and Video"
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HREF="guidevideo.html"><LINK
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REL="PREVIOUS"
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TITLE="Graphics and Video"
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HREF="guidevideo.html"><LINK
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REL="NEXT"
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TITLE="Input handling"
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HREF="guideinput.html"></HEAD
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><BODY
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CLASS="SECT1"
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BGCOLOR="#FFF8DC"
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TEXT="#000000"
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LINK="#0000ee"
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VLINK="#551a8b"
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ALINK="#ff0000"
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><DIV
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CLASS="NAVHEADER"
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><TABLE
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WIDTH="100%"
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BORDER="0"
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CELLPADDING="0"
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CELLSPACING="0"
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><TR
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><TH
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COLSPAN="3"
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ALIGN="center"
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>SDL Library Documentation</TH
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></TR
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><TR
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><TD
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WIDTH="10%"
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ALIGN="left"
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VALIGN="bottom"
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><A
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HREF="guidevideo.html"
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>Prev</A
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></TD
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><TD
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WIDTH="80%"
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ALIGN="center"
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VALIGN="bottom"
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>Chapter 2. Graphics and Video</TD
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><TD
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WIDTH="10%"
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ALIGN="right"
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VALIGN="bottom"
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><A
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HREF="guideinput.html"
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>Next</A
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></TD
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></TR
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></TABLE
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><HR
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ALIGN="LEFT"
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WIDTH="100%"></DIV
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><DIV
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CLASS="SECT1"
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><H1
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CLASS="SECT1"
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><A
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NAME="GUIDEVIDEOOPENGL"
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>Using OpenGL With SDL</A
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></H1
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><P
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>SDL has the ability to create and use OpenGL contexts on several platforms(Linux/X11, Win32, BeOS, MacOS Classic/Toolbox, MacOS X, FreeBSD/X11 and Solaris/X11). This allows you to use SDL's audio, event handling, threads and times in your OpenGL applications (a function often performed by GLUT).</P
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><DIV
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CLASS="SECT2"
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><H2
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CLASS="SECT2"
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><A
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NAME="AEN103"
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>Initialisation</A
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></H2
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><P
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>Initialising SDL to use OpenGL is not very different to initialising SDL normally. There are three differences; you must pass <TT
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CLASS="LITERAL"
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>SDL_OPENGL</TT
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> to <A
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HREF="sdlsetvideomode.html"
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><TT
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CLASS="FUNCTION"
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>SDL_SetVideoMode</TT
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></A
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>, you must specify several GL attributes (depth buffer size, framebuffer sizes) using <A
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HREF="sdlglsetattribute.html"
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><TT
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CLASS="FUNCTION"
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>SDL_GL_SetAttribute</TT
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></A
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> and finally, if you wish to use double buffering you must specify it as a GL attribute, <I
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CLASS="EMPHASIS"
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>not</I
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> by passing the <TT
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CLASS="LITERAL"
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>SDL_DOUBLEBUF</TT
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> flag to <TT
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CLASS="FUNCTION"
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>SDL_SetVideoMode</TT
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>.</P
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><DIV
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CLASS="EXAMPLE"
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><A
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NAME="AEN114"
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></A
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><P
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><B
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>Example 2-7. Initializing SDL with OpenGL</B
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></P
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><PRE
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CLASS="PROGRAMLISTING"
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> /* Information about the current video settings. */
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const SDL_VideoInfo* info = NULL;
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/* Dimensions of our window. */
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int width = 0;
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int height = 0;
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/* Color depth in bits of our window. */
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int bpp = 0;
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/* Flags we will pass into SDL_SetVideoMode. */
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int flags = 0;
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/* First, initialize SDL's video subsystem. */
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if( SDL_Init( SDL_INIT_VIDEO ) < 0 ) {
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/* Failed, exit. */
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fprintf( stderr, "Video initialization failed: %s\n",
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SDL_GetError( ) );
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quit_tutorial( 1 );
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}
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/* Let's get some video information. */
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info = SDL_GetVideoInfo( );
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if( !info ) {
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/* This should probably never happen. */
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fprintf( stderr, "Video query failed: %s\n",
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SDL_GetError( ) );
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quit_tutorial( 1 );
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}
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/*
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* Set our width/height to 640/480 (you would
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* of course let the user decide this in a normal
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* app). We get the bpp we will request from
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* the display. On X11, VidMode can't change
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* resolution, so this is probably being overly
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* safe. Under Win32, ChangeDisplaySettings
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* can change the bpp.
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*/
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width = 640;
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height = 480;
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bpp = info->vfmt->BitsPerPixel;
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/*
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* Now, we want to setup our requested
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* window attributes for our OpenGL window.
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* We want *at least* 5 bits of red, green
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* and blue. We also want at least a 16-bit
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* depth buffer.
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*
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* The last thing we do is request a double
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* buffered window. '1' turns on double
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* buffering, '0' turns it off.
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*
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* Note that we do not use SDL_DOUBLEBUF in
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* the flags to SDL_SetVideoMode. That does
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* not affect the GL attribute state, only
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* the standard 2D blitting setup.
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*/
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SDL_GL_SetAttribute( SDL_GL_RED_SIZE, 5 );
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SDL_GL_SetAttribute( SDL_GL_GREEN_SIZE, 5 );
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SDL_GL_SetAttribute( SDL_GL_BLUE_SIZE, 5 );
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SDL_GL_SetAttribute( SDL_GL_DEPTH_SIZE, 16 );
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SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 );
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/*
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* We want to request that SDL provide us
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* with an OpenGL window, in a fullscreen
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* video mode.
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*
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* EXERCISE:
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* Make starting windowed an option, and
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* handle the resize events properly with
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* glViewport.
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*/
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flags = SDL_OPENGL | SDL_FULLSCREEN;
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/*
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* Set the video mode
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*/
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if( SDL_SetVideoMode( width, height, bpp, flags ) == 0 ) {
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/*
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* This could happen for a variety of reasons,
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* including DISPLAY not being set, the specified
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* resolution not being available, etc.
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*/
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fprintf( stderr, "Video mode set failed: %s\n",
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SDL_GetError( ) );
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quit_tutorial( 1 );
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}</PRE
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></DIV
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></DIV
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><DIV
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CLASS="SECT2"
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><H2
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CLASS="SECT2"
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><A
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NAME="AEN117"
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>Drawing</A
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></H2
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><P
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>Apart from initialisation, using OpenGL within SDL is the same as using OpenGL
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with any other API, e.g. GLUT. You still use all the same function calls and
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data types. However if you are using a double-buffered display, then you must
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use
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<A
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HREF="sdlglswapbuffers.html"
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><TT
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CLASS="FUNCTION"
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>SDL_GL_SwapBuffers()</TT
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></A
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>
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to swap the buffers and update the display. To request double-buffering
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with OpenGL, use
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<A
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HREF="sdlglsetattribute.html"
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><TT
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CLASS="FUNCTION"
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>SDL_GL_SetAttribute</TT
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></A
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>
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with <TT
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CLASS="LITERAL"
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>SDL_GL_DOUBLEBUFFER</TT
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>, and use
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<A
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HREF="sdlglgetattribute.html"
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><TT
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CLASS="FUNCTION"
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>SDL_GL_GetAttribute</TT
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></A
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>
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to see if you actually got it.</P
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><P
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>A full example code listing is now presented below.</P
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><DIV
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CLASS="EXAMPLE"
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><A
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NAME="AEN128"
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></A
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><P
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><B
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>Example 2-8. SDL and OpenGL</B
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></P
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><PRE
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CLASS="PROGRAMLISTING"
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>/*
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* SDL OpenGL Tutorial.
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* (c) Michael Vance, 2000
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* briareos@lokigames.com
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*
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* Distributed under terms of the LGPL.
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*/
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#include <SDL/SDL.h>
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#include <GL/gl.h>
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#include <GL/glu.h>
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#include <stdio.h>
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#include <stdlib.h>
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static GLboolean should_rotate = GL_TRUE;
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static void quit_tutorial( int code )
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{
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/*
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* Quit SDL so we can release the fullscreen
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* mode and restore the previous video settings,
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* etc.
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*/
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SDL_Quit( );
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/* Exit program. */
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exit( code );
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}
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static void handle_key_down( SDL_keysym* keysym )
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{
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/*
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* We're only interested if 'Esc' has
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* been presssed.
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*
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* EXERCISE:
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* Handle the arrow keys and have that change the
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* viewing position/angle.
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*/
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switch( keysym->sym ) {
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case SDLK_ESCAPE:
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quit_tutorial( 0 );
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break;
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case SDLK_SPACE:
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should_rotate = !should_rotate;
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break;
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default:
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break;
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}
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}
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static void process_events( void )
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{
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/* Our SDL event placeholder. */
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SDL_Event event;
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/* Grab all the events off the queue. */
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while( SDL_PollEvent( &event ) ) {
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switch( event.type ) {
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case SDL_KEYDOWN:
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/* Handle key presses. */
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handle_key_down( &event.key.keysym );
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break;
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case SDL_QUIT:
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/* Handle quit requests (like Ctrl-c). */
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quit_tutorial( 0 );
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break;
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}
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}
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}
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static void draw_screen( void )
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{
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/* Our angle of rotation. */
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static float angle = 0.0f;
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/*
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* EXERCISE:
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* Replace this awful mess with vertex
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* arrays and a call to glDrawElements.
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*
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* EXERCISE:
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* After completing the above, change
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* it to use compiled vertex arrays.
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*
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* EXERCISE:
|
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* Verify my windings are correct here ;).
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*/
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static GLfloat v0[] = { -1.0f, -1.0f, 1.0f };
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static GLfloat v1[] = { 1.0f, -1.0f, 1.0f };
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static GLfloat v2[] = { 1.0f, 1.0f, 1.0f };
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static GLfloat v3[] = { -1.0f, 1.0f, 1.0f };
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static GLfloat v4[] = { -1.0f, -1.0f, -1.0f };
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static GLfloat v5[] = { 1.0f, -1.0f, -1.0f };
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static GLfloat v6[] = { 1.0f, 1.0f, -1.0f };
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static GLfloat v7[] = { -1.0f, 1.0f, -1.0f };
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static GLubyte red[] = { 255, 0, 0, 255 };
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static GLubyte green[] = { 0, 255, 0, 255 };
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static GLubyte blue[] = { 0, 0, 255, 255 };
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static GLubyte white[] = { 255, 255, 255, 255 };
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static GLubyte yellow[] = { 0, 255, 255, 255 };
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static GLubyte black[] = { 0, 0, 0, 255 };
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static GLubyte orange[] = { 255, 255, 0, 255 };
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static GLubyte purple[] = { 255, 0, 255, 0 };
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/* Clear the color and depth buffers. */
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glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
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/* We don't want to modify the projection matrix. */
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glMatrixMode( GL_MODELVIEW );
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glLoadIdentity( );
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/* Move down the z-axis. */
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glTranslatef( 0.0, 0.0, -5.0 );
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/* Rotate. */
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glRotatef( angle, 0.0, 1.0, 0.0 );
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if( should_rotate ) {
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if( ++angle > 360.0f ) {
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angle = 0.0f;
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}
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}
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/* Send our triangle data to the pipeline. */
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|
|
glBegin( GL_TRIANGLES );
|
||
|
|
|
||
|
|
glColor4ubv( red );
|
||
|
|
glVertex3fv( v0 );
|
||
|
|
glColor4ubv( green );
|
||
|
|
glVertex3fv( v1 );
|
||
|
|
glColor4ubv( blue );
|
||
|
|
glVertex3fv( v2 );
|
||
|
|
|
||
|
|
glColor4ubv( red );
|
||
|
|
glVertex3fv( v0 );
|
||
|
|
glColor4ubv( blue );
|
||
|
|
glVertex3fv( v2 );
|
||
|
|
glColor4ubv( white );
|
||
|
|
glVertex3fv( v3 );
|
||
|
|
|
||
|
|
glColor4ubv( green );
|
||
|
|
glVertex3fv( v1 );
|
||
|
|
glColor4ubv( black );
|
||
|
|
glVertex3fv( v5 );
|
||
|
|
glColor4ubv( orange );
|
||
|
|
glVertex3fv( v6 );
|
||
|
|
|
||
|
|
glColor4ubv( green );
|
||
|
|
glVertex3fv( v1 );
|
||
|
|
glColor4ubv( orange );
|
||
|
|
glVertex3fv( v6 );
|
||
|
|
glColor4ubv( blue );
|
||
|
|
glVertex3fv( v2 );
|
||
|
|
|
||
|
|
glColor4ubv( black );
|
||
|
|
glVertex3fv( v5 );
|
||
|
|
glColor4ubv( yellow );
|
||
|
|
glVertex3fv( v4 );
|
||
|
|
glColor4ubv( purple );
|
||
|
|
glVertex3fv( v7 );
|
||
|
|
|
||
|
|
glColor4ubv( black );
|
||
|
|
glVertex3fv( v5 );
|
||
|
|
glColor4ubv( purple );
|
||
|
|
glVertex3fv( v7 );
|
||
|
|
glColor4ubv( orange );
|
||
|
|
glVertex3fv( v6 );
|
||
|
|
|
||
|
|
glColor4ubv( yellow );
|
||
|
|
glVertex3fv( v4 );
|
||
|
|
glColor4ubv( red );
|
||
|
|
glVertex3fv( v0 );
|
||
|
|
glColor4ubv( white );
|
||
|
|
glVertex3fv( v3 );
|
||
|
|
|
||
|
|
glColor4ubv( yellow );
|
||
|
|
glVertex3fv( v4 );
|
||
|
|
glColor4ubv( white );
|
||
|
|
glVertex3fv( v3 );
|
||
|
|
glColor4ubv( purple );
|
||
|
|
glVertex3fv( v7 );
|
||
|
|
|
||
|
|
glColor4ubv( white );
|
||
|
|
glVertex3fv( v3 );
|
||
|
|
glColor4ubv( blue );
|
||
|
|
glVertex3fv( v2 );
|
||
|
|
glColor4ubv( orange );
|
||
|
|
glVertex3fv( v6 );
|
||
|
|
|
||
|
|
glColor4ubv( white );
|
||
|
|
glVertex3fv( v3 );
|
||
|
|
glColor4ubv( orange );
|
||
|
|
glVertex3fv( v6 );
|
||
|
|
glColor4ubv( purple );
|
||
|
|
glVertex3fv( v7 );
|
||
|
|
|
||
|
|
glColor4ubv( green );
|
||
|
|
glVertex3fv( v1 );
|
||
|
|
glColor4ubv( red );
|
||
|
|
glVertex3fv( v0 );
|
||
|
|
glColor4ubv( yellow );
|
||
|
|
glVertex3fv( v4 );
|
||
|
|
|
||
|
|
glColor4ubv( green );
|
||
|
|
glVertex3fv( v1 );
|
||
|
|
glColor4ubv( yellow );
|
||
|
|
glVertex3fv( v4 );
|
||
|
|
glColor4ubv( black );
|
||
|
|
glVertex3fv( v5 );
|
||
|
|
|
||
|
|
glEnd( );
|
||
|
|
|
||
|
|
/*
|
||
|
|
* EXERCISE:
|
||
|
|
* Draw text telling the user that 'Spc'
|
||
|
|
* pauses the rotation and 'Esc' quits.
|
||
|
|
* Do it using vetors and textured quads.
|
||
|
|
*/
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Swap the buffers. This this tells the driver to
|
||
|
|
* render the next frame from the contents of the
|
||
|
|
* back-buffer, and to set all rendering operations
|
||
|
|
* to occur on what was the front-buffer.
|
||
|
|
*
|
||
|
|
* Double buffering prevents nasty visual tearing
|
||
|
|
* from the application drawing on areas of the
|
||
|
|
* screen that are being updated at the same time.
|
||
|
|
*/
|
||
|
|
SDL_GL_SwapBuffers( );
|
||
|
|
}
|
||
|
|
|
||
|
|
static void setup_opengl( int width, int height )
|
||
|
|
{
|
||
|
|
float ratio = (float) width / (float) height;
|
||
|
|
|
||
|
|
/* Our shading model--Gouraud (smooth). */
|
||
|
|
glShadeModel( GL_SMOOTH );
|
||
|
|
|
||
|
|
/* Culling. */
|
||
|
|
glCullFace( GL_BACK );
|
||
|
|
glFrontFace( GL_CCW );
|
||
|
|
glEnable( GL_CULL_FACE );
|
||
|
|
|
||
|
|
/* Set the clear color. */
|
||
|
|
glClearColor( 0, 0, 0, 0 );
|
||
|
|
|
||
|
|
/* Setup our viewport. */
|
||
|
|
glViewport( 0, 0, width, height );
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Change to the projection matrix and set
|
||
|
|
* our viewing volume.
|
||
|
|
*/
|
||
|
|
glMatrixMode( GL_PROJECTION );
|
||
|
|
glLoadIdentity( );
|
||
|
|
/*
|
||
|
|
* EXERCISE:
|
||
|
|
* Replace this with a call to glFrustum.
|
||
|
|
*/
|
||
|
|
gluPerspective( 60.0, ratio, 1.0, 1024.0 );
|
||
|
|
}
|
||
|
|
|
||
|
|
int main( int argc, char* argv[] )
|
||
|
|
{
|
||
|
|
/* Information about the current video settings. */
|
||
|
|
const SDL_VideoInfo* info = NULL;
|
||
|
|
/* Dimensions of our window. */
|
||
|
|
int width = 0;
|
||
|
|
int height = 0;
|
||
|
|
/* Color depth in bits of our window. */
|
||
|
|
int bpp = 0;
|
||
|
|
/* Flags we will pass into SDL_SetVideoMode. */
|
||
|
|
int flags = 0;
|
||
|
|
|
||
|
|
/* First, initialize SDL's video subsystem. */
|
||
|
|
if( SDL_Init( SDL_INIT_VIDEO ) < 0 ) {
|
||
|
|
/* Failed, exit. */
|
||
|
|
fprintf( stderr, "Video initialization failed: %s\n",
|
||
|
|
SDL_GetError( ) );
|
||
|
|
quit_tutorial( 1 );
|
||
|
|
}
|
||
|
|
|
||
|
|
/* Let's get some video information. */
|
||
|
|
info = SDL_GetVideoInfo( );
|
||
|
|
|
||
|
|
if( !info ) {
|
||
|
|
/* This should probably never happen. */
|
||
|
|
fprintf( stderr, "Video query failed: %s\n",
|
||
|
|
SDL_GetError( ) );
|
||
|
|
quit_tutorial( 1 );
|
||
|
|
}
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Set our width/height to 640/480 (you would
|
||
|
|
* of course let the user decide this in a normal
|
||
|
|
* app). We get the bpp we will request from
|
||
|
|
* the display. On X11, VidMode can't change
|
||
|
|
* resolution, so this is probably being overly
|
||
|
|
* safe. Under Win32, ChangeDisplaySettings
|
||
|
|
* can change the bpp.
|
||
|
|
*/
|
||
|
|
width = 640;
|
||
|
|
height = 480;
|
||
|
|
bpp = info->vfmt->BitsPerPixel;
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Now, we want to setup our requested
|
||
|
|
* window attributes for our OpenGL window.
|
||
|
|
* We want *at least* 5 bits of red, green
|
||
|
|
* and blue. We also want at least a 16-bit
|
||
|
|
* depth buffer.
|
||
|
|
*
|
||
|
|
* The last thing we do is request a double
|
||
|
|
* buffered window. '1' turns on double
|
||
|
|
* buffering, '0' turns it off.
|
||
|
|
*
|
||
|
|
* Note that we do not use SDL_DOUBLEBUF in
|
||
|
|
* the flags to SDL_SetVideoMode. That does
|
||
|
|
* not affect the GL attribute state, only
|
||
|
|
* the standard 2D blitting setup.
|
||
|
|
*/
|
||
|
|
SDL_GL_SetAttribute( SDL_GL_RED_SIZE, 5 );
|
||
|
|
SDL_GL_SetAttribute( SDL_GL_GREEN_SIZE, 5 );
|
||
|
|
SDL_GL_SetAttribute( SDL_GL_BLUE_SIZE, 5 );
|
||
|
|
SDL_GL_SetAttribute( SDL_GL_DEPTH_SIZE, 16 );
|
||
|
|
SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 );
|
||
|
|
|
||
|
|
/*
|
||
|
|
* We want to request that SDL provide us
|
||
|
|
* with an OpenGL window, in a fullscreen
|
||
|
|
* video mode.
|
||
|
|
*
|
||
|
|
* EXERCISE:
|
||
|
|
* Make starting windowed an option, and
|
||
|
|
* handle the resize events properly with
|
||
|
|
* glViewport.
|
||
|
|
*/
|
||
|
|
flags = SDL_OPENGL | SDL_FULLSCREEN;
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Set the video mode
|
||
|
|
*/
|
||
|
|
if( SDL_SetVideoMode( width, height, bpp, flags ) == 0 ) {
|
||
|
|
/*
|
||
|
|
* This could happen for a variety of reasons,
|
||
|
|
* including DISPLAY not being set, the specified
|
||
|
|
* resolution not being available, etc.
|
||
|
|
*/
|
||
|
|
fprintf( stderr, "Video mode set failed: %s\n",
|
||
|
|
SDL_GetError( ) );
|
||
|
|
quit_tutorial( 1 );
|
||
|
|
}
|
||
|
|
|
||
|
|
/*
|
||
|
|
* At this point, we should have a properly setup
|
||
|
|
* double-buffered window for use with OpenGL.
|
||
|
|
*/
|
||
|
|
setup_opengl( width, height );
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Now we want to begin our normal app process--
|
||
|
|
* an event loop with a lot of redrawing.
|
||
|
|
*/
|
||
|
|
while( 1 ) {
|
||
|
|
/* Process incoming events. */
|
||
|
|
process_events( );
|
||
|
|
/* Draw the screen. */
|
||
|
|
draw_screen( );
|
||
|
|
}
|
||
|
|
|
||
|
|
/*
|
||
|
|
* EXERCISE:
|
||
|
|
* Record timings using SDL_GetTicks() and
|
||
|
|
* and print out frames per second at program
|
||
|
|
* end.
|
||
|
|
*/
|
||
|
|
|
||
|
|
/* Never reached. */
|
||
|
|
return 0;
|
||
|
|
}</PRE
|
||
|
|
></DIV
|
||
|
|
></DIV
|
||
|
|
></DIV
|
||
|
|
><DIV
|
||
|
|
CLASS="NAVFOOTER"
|
||
|
|
><HR
|
||
|
|
ALIGN="LEFT"
|
||
|
|
WIDTH="100%"><TABLE
|
||
|
|
WIDTH="100%"
|
||
|
|
BORDER="0"
|
||
|
|
CELLPADDING="0"
|
||
|
|
CELLSPACING="0"
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
WIDTH="33%"
|
||
|
|
ALIGN="left"
|
||
|
|
VALIGN="top"
|
||
|
|
><A
|
||
|
|
HREF="guidevideo.html"
|
||
|
|
>Prev</A
|
||
|
|
></TD
|
||
|
|
><TD
|
||
|
|
WIDTH="34%"
|
||
|
|
ALIGN="center"
|
||
|
|
VALIGN="top"
|
||
|
|
><A
|
||
|
|
HREF="index.html"
|
||
|
|
>Home</A
|
||
|
|
></TD
|
||
|
|
><TD
|
||
|
|
WIDTH="33%"
|
||
|
|
ALIGN="right"
|
||
|
|
VALIGN="top"
|
||
|
|
><A
|
||
|
|
HREF="guideinput.html"
|
||
|
|
>Next</A
|
||
|
|
></TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
WIDTH="33%"
|
||
|
|
ALIGN="left"
|
||
|
|
VALIGN="top"
|
||
|
|
>Graphics and Video</TD
|
||
|
|
><TD
|
||
|
|
WIDTH="34%"
|
||
|
|
ALIGN="center"
|
||
|
|
VALIGN="top"
|
||
|
|
><A
|
||
|
|
HREF="guidevideo.html"
|
||
|
|
>Up</A
|
||
|
|
></TD
|
||
|
|
><TD
|
||
|
|
WIDTH="33%"
|
||
|
|
ALIGN="right"
|
||
|
|
VALIGN="top"
|
||
|
|
>Input handling</TD
|
||
|
|
></TR
|
||
|
|
></TABLE
|
||
|
|
></DIV
|
||
|
|
></BODY
|
||
|
|
></HTML
|
||
|
|
>
|