SDL OPENGL 在linux ubuntu示例

gl画纹理texture

/*
* SDL OpenGL Tutorial.
* (c) Michael Vance, 2000
* briareos@lokigames.com
*
* Distributed under terms of the LGPL.
*/

#include <SDL/SDL.h>
#include <GL/gl.h>
#include <GL/glu.h>

#include <stdio.h>
#include <stdlib.h>

/*******************************************************************
* *
* Using SDL With OpenGL *
* *
* Tutorial by Kyle Foley (sdw) *
* *
* http://gpwiki.org/index.php/SDL:Tutorials:Using_SDL_with_OpenGL *
* *
*******************************************************************/

#include <stdio.h>

int main(int argc, char *argv[])
{
SDL_Surface *screen;

// Slightly different SDL initialization
if ( SDL_Init(SDL_INIT_VIDEO) != 0 ) {
printf("Unable to initialize SDL: %s ", SDL_GetError());
return 1;
}

SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 ); // *new*

screen = SDL_SetVideoMode( 640, 480, 16, SDL_OPENGL | SDL_FULLSCREEN ); // *changed*
if ( !screen ) {
printf("Unable to set video mode: %s ", SDL_GetError());
return 1;
}

// Set the OpenGL state after creating the context with SDL_SetVideoMode

glClearColor( 0, 0, 0, 0 );

glEnable( GL_TEXTURE_2D ); // Need this to display a texture

glViewport( 0, 0, 640, 480 );

glMatrixMode( GL_PROJECTION );
glLoadIdentity();

glOrtho( 0, 640, 480, 0, -1, 1 );

glMatrixMode( GL_MODELVIEW );
glLoadIdentity();

// Load the OpenGL texture

GLuint texture; // Texture object handle
SDL_Surface *surface; // Gives us the information to make the texture

if ( (surface = SDL_LoadBMP("image.bmp")) ) {

// Check that the image's width is a power of 2
if ( (surface->w & (surface->w - 1)) != 0 ) {
printf("warning: image.bmp's width is not a power of 2 ");
}

// Also check if the height is a power of 2
if ( (surface->h & (surface->h - 1)) != 0 ) {
printf("warning: image.bmp's height is not a power of 2 ");
}

// Have OpenGL generate a texture object handle for us
glGenTextures( 1, &texture );

// Bind the texture object
glBindTexture( GL_TEXTURE_2D, texture );

// Set the texture's stretching properties
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );

// Edit the texture object's image data using the information SDL_Surface gives us
glTexImage2D( GL_TEXTURE_2D, 0, 3, surface->w, surface->h, 0,
GL_BGR, GL_UNSIGNED_BYTE, surface->pixels );
}
else {
printf("SDL could not load image.bmp: %s ", SDL_GetError());
SDL_Quit();
return 1;
}

// Free the SDL_Surface only if it was successfully created
if ( surface ) {
SDL_FreeSurface( surface );
}

// Clear the screen before drawing
glClear( GL_COLOR_BUFFER_BIT );

// Bind the texture to which subsequent calls refer to
glBindTexture( GL_TEXTURE_2D, texture );

glBegin( GL_QUADS );
// Top-left vertex (corner)
glTexCoord2i( 0, 0 );
glVertex3f( 100, 100, 0 );

// Bottom-left vertex (corner)
glTexCoord2i( 1, 0 );
glVertex3f( 228, 100, 0 );

// Bottom-right vertex (corner)
glTexCoord2i( 1, 1 );
glVertex3f( 228, 228, 0 );

// Top-right vertex (corner)
glTexCoord2i( 0, 1 );
glVertex3f( 100, 228, 0 );
glEnd();

SDL_GL_SwapBuffers();

// Wait for 3 seconds to give us a chance to see the image
SDL_Delay(30000);

// Now we can delete the OpenGL texture and close down SDL
glDeleteTextures( 1, &texture );

SDL_Quit();

return 0;
}

---

旋转球
http://www.libsdl.org/docs/html/guidevideoopengl.html
/*
 * SDL OpenGL Tutorial.
 * (c) Michael Vance, 2000
 * briareos@lokigames.com
 *
 * Distributed under terms of the LGPL. 
 */

#include <SDL/SDL.h>
#include <GL/gl.h>
#include <GL/glu.h>

#include <stdio.h>
#include <stdlib.h>

static GLboolean should_rotate = GL_TRUE;

static void quit_tutorial( int code )
{
    /*
     * Quit SDL so we can release the fullscreen
     * mode and restore the previous video settings,
     * etc.
     */
    SDL_Quit( );

    /* Exit program. */
    exit( code );
}

static void handle_key_down( SDL_keysym* keysym )
{

    /* 
     * We're only interested if 'Esc' has
     * been presssed.
     *
     * EXERCISE: 
     * Handle the arrow keys and have that change the
     * viewing position/angle.
     */
    switch( keysym->sym ) {
    case SDLK_ESCAPE:
        quit_tutorial( 0 );
        break;
    case SDLK_SPACE:
        should_rotate = !should_rotate;
        break;
    default:
        break;
    }

}

static void process_events( void )
{
    /* Our SDL event placeholder. */
    SDL_Event event;

    /* Grab all the events off the queue. */
    while( SDL_PollEvent( &event ) ) {

        switch( event.type ) {
        case SDL_KEYDOWN:
            /* Handle key presses. */
            handle_key_down( &event.key.keysym );
            break;
        case SDL_QUIT:
            /* Handle quit requests (like Ctrl-c). */
            quit_tutorial( 0 );
            break;
        }

    }

}

static void draw_screen( void )
{
    /* Our angle of rotation. */
    static float angle = 0.0f;

    /*
     * EXERCISE:
     * Replace this awful mess with vertex
     * arrays and a call to glDrawElements.
     *
     * EXERCISE:
     * After completing the above, change
     * it to use compiled vertex arrays.
     *
     * EXERCISE:
     * Verify my windings are correct here ;).
     */
    static GLfloat v0[] = { -1.0f, -1.0f,  1.0f };
    static GLfloat v1[] = {  1.0f, -1.0f,  1.0f };
    static GLfloat v2[] = {  1.0f,  1.0f,  1.0f };
    static GLfloat v3[] = { -1.0f,  1.0f,  1.0f };
    static GLfloat v4[] = { -1.0f, -1.0f, -1.0f };
    static GLfloat v5[] = {  1.0f, -1.0f, -1.0f };
    static GLfloat v6[] = {  1.0f,  1.0f, -1.0f };
    static GLfloat v7[] = { -1.0f,  1.0f, -1.0f };
    static GLubyte red[]    = { 255,   0,   0, 255 };
    static GLubyte green[]  = {   0, 255,   0, 255 };
    static GLubyte blue[]   = {   0,   0, 255, 255 };
    static GLubyte white[]  = { 255, 255, 255, 255 };
    static GLubyte yellow[] = {   0, 255, 255, 255 };
    static GLubyte black[]  = {   0,   0,   0, 255 };
    static GLubyte orange[] = { 255, 255,   0, 255 };
    static GLubyte purple[] = { 255,   0, 255,   0 };

    /* Clear the color and depth buffers. */
    glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

    /* We don't want to modify the projection matrix. */
    glMatrixMode( GL_MODELVIEW );
    glLoadIdentity( );

    /* Move down the z-axis. */
    glTranslatef( 0.0, 0.0, -5.0 );

    /* Rotate. */
    glRotatef( angle, 0.0, 1.0, 0.0 );

    if( should_rotate ) {

        if( ++angle > 360.0f ) {
            angle = 0.0f;
        }

    }

    /* Send our triangle data to the pipeline. */
    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
",
             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
",
             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
",
             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;
}

---

显示黑屏的例子：

#include <stdio.h>
#include <stdlib.h>
#include <GL/gl.h>
#include <GL/glu.h>
#include <SDL/SDL.h>

/* 屏幕宽，高和颜色位数 */
#define SCREEN_WIDTH 640
#define SCREEN_HEIGHT 480
#define SCREEN_BPP 16

/* 设置布尔值 */
#define TRUE 1
#define FALSE 0

/* SDL表面 */
SDL_Surface *surface;

/* 用来释放／销毁程序资源，并返回桌面 */
void Quit(int returnCode) {
/* 清除窗口 */
SDL_Quit();

/* 退出 */
exit(returnCode);
}

/* 窗口更改后重新设置视点（观察点） */
int resizeWindow(int width, int height) {
/* 高与宽的比例 */
GLfloat ratio;

/* 防止除零 */
if (height == 0)
height = 1;

ratio = (GLfloat) width / (GLfloat) height;

/* 设置视点 */
glViewport(0, 0, (GLint) width, (GLint) height);

/* 选择投影矩阵 */
glMatrixMode(GL_PROJECTION);
glLoadIdentity();

/* 设置透视 */
gluPerspective(45.0f, ratio, 0.1f, 100.0f);

/* 选择模型观察矩阵 */
glMatrixMode(GL_MODELVIEW);

/* 重置模型观察矩阵 */
glLoadIdentity();

return (TRUE);
}

/* 获得键盘按键事件 */
void handleKeyPress(SDL_keysym *keysym) {
switch (keysym->sym) {
case SDLK_ESCAPE:
/* ESC按下时 */
Quit(0);
break;
case SDLK_F1:
/* F1按下时
* 触发全屏模式
*/
SDL_WM_ToggleFullScreen(surface);
break;
default:
break;
}

return;
}

/* OpenGL初始化函数 */
int initGL(void) {

/* 启用阴影平滑 */
glShadeModel(GL_SMOOTH);

/* 设置黑色背景 */
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);

/* 设置深度缓存 */
glClearDepth(1.0f);

/* 启用深度测试 */
glEnable(GL_DEPTH_TEST);

/* 所作深度测试类型 */
glDepthFunc(GL_LEQUAL);

/* 告知系统对透视进行修正 */
glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);

return (TRUE);
}

/* 绘制代码 */
int drawGLScene(void) {
/* 计算fps */
static GLint T0 = 0;
static GLint Frames = 0;

/* 清除屏幕及深度缓冲 */
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glLoadIdentity();

/* 绘制屏幕 */
SDL_GL_SwapBuffers();

/* 自增长桢的计算 */
Frames++;
{
GLint t = SDL_GetTicks();
if (t - T0 >= 5000) {
GLfloat seconds = (t - T0) / 1000.0;
GLfloat fps = Frames / seconds;
printf("%d frames in %g seconds = %g FPS ", Frames, seconds, fps);
T0 = t;
Frames = 0;
}
}

return (TRUE);
}

/* 程序主函数 */
int main(int argc, char **argv) {
/* 通过SDL_SetVideoMode标志 */
int videoFlags;
/* 主循环变量 */
int done = FALSE;
/* SDL事件 */
SDL_Event event;
/* 显示一些信息在屏幕 */
const SDL_VideoInfo *videoInfo;
/* 窗口激活标志 */
int isActive = TRUE;

/* 初始化 SDL */
if (SDL_Init(SDL_INIT_VIDEO) < 0) {
fprintf(stderr, "Video initialization failed: %s ", SDL_GetError());
Quit(1);
}

/* 获得视频信息 */
videoInfo = SDL_GetVideoInfo();

if (!videoInfo) {
fprintf(stderr, "Video query failed: %s ", SDL_GetError());
Quit(1);
}

/* 通过SDL_SetVideoMode标志 */
videoFlags = SDL_OPENGL; /* 在SDL中启用OpenGL */
videoFlags |= SDL_GL_DOUBLEBUFFER; /* 启用双缓冲 */
videoFlags |= SDL_HWPALETTE; /* 硬件保存调色板 */
videoFlags |= SDL_RESIZABLE; /* 窗口可更改 */

/* 检测表面是否可以保存入内存 */
if (videoInfo->hw_available){
printf("===support. ");
videoFlags |= SDL_HWSURFACE;
}else{
printf("===not support. ");
videoFlags |= SDL_SWSURFACE;
}

/* 测试硬件翻转 */
if (videoInfo->blit_hw)
videoFlags |= SDL_HWACCEL;

/* 设置OpenGL双缓冲 */
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);

/* 获得SDL表面 */
surface = SDL_SetVideoMode(SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP, videoFlags);

/* 验证表面 */
if (!surface) {
fprintf(stderr, "Video mode set failed: %s ", SDL_GetError());
Quit(1);
}

/* 初始化 OpenGL */
if (initGL() == FALSE) {
fprintf(stderr, "Could not initialize OpenGL. ");
Quit(1);
}

/* 初始化窗口 */
resizeWindow(SCREEN_WIDTH, SCREEN_HEIGHT);

/* 等待事件 */
while (!done) {
/* 获得事件队列 */

while (SDL_PollEvent(&event)) {
switch (event.type) {
case SDL_ACTIVEEVENT:
/* 不在焦点时候或最小化，不需要绘制
*/
if (event.active.gain == 0)
isActive = FALSE;
else
isActive = TRUE;
break;
case SDL_VIDEORESIZE:
/* 获得改变窗口事件 */
surface = SDL_SetVideoMode(event.resize.w, event.resize.h, 16, videoFlags);
if (!surface) {
fprintf(stderr, "Could not get a surface after resize: %s ", SDL_GetError());
Quit(1);
}
resizeWindow(event.resize.w, event.resize.h);
break;
case SDL_KEYDOWN:
/* 获得键盘按下 */
handleKeyPress(&event.key.keysym);
break;
case SDL_QUIT:
/* 获得退出请求 */
done = TRUE;
break;
default:
break;
}
}

/* 绘制场景 */
if (isActive)
drawGLScene();
}

/* 清除本身并退出 */
Quit(0);

/* 不可能执行这里了 */
return (0);
}