| /******************************************************************* |
| * * |
| * Using SDL With OpenGL * |
| * * |
| * Tutorial by Kyle Foley (sdw) * |
| * * |
| * http://gpwiki.org/index.php/SDL:Tutorials:Using_SDL_with_OpenGL * |
| * * |
| *******************************************************************/ |
| |
| /* |
| THIS WORK, INCLUDING THE SOURCE CODE, DOCUMENTATION |
| AND RELATED MEDIA AND DATA, IS PLACED INTO THE PUBLIC DOMAIN. |
| |
| THE ORIGINAL AUTHOR IS KYLE FOLEY. |
| |
| THIS SOFTWARE IS PROVIDED AS-IS WITHOUT WARRANTY |
| OF ANY KIND, NOT EVEN THE IMPLIED WARRANTY OF |
| MERCHANTABILITY. THE AUTHOR OF THIS SOFTWARE, |
| ASSUMES _NO_ RESPONSIBILITY FOR ANY CONSEQUENCE |
| RESULTING FROM THE USE, MODIFICATION, OR |
| REDISTRIBUTION OF THIS SOFTWARE. |
| */ |
| |
| #ifndef __EMSCRIPTEN__ |
| #define USE_GLEW 0 |
| #endif |
| |
| #if USE_GLEW |
| #include "GL/glew.h" |
| #endif |
| |
| #include "SDL/SDL.h" |
| #include "SDL/SDL_image.h" |
| #if !USE_GLEW |
| #include "SDL/SDL_opengl.h" |
| #endif |
| |
| #include <stdio.h> |
| #include <string.h> |
| #include <assert.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\n", SDL_GetError()); |
| return 1; |
| } |
| |
| SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 ); // *new* |
| |
| screen = SDL_SetVideoMode( 640, 480, 16, SDL_OPENGL ); // *changed* |
| if ( !screen ) { |
| printf("Unable to set video mode: %s\n", SDL_GetError()); |
| return 1; |
| } |
| |
| // Set the OpenGL state after creating the context with SDL_SetVideoMode |
| |
| glClearColor( 0, 0, 0, 0 ); |
| |
| #ifndef __EMSCRIPTEN__ |
| glEnable( GL_TEXTURE_2D ); // Need this to display a texture XXX unnecessary in OpenGL ES 2.0/WebGL |
| #endif |
| |
| glViewport( 0, 0, 640, 480 ); |
| |
| glMatrixMode( GL_MODELVIEW ); |
| glLoadIdentity(); |
| |
| // Clear the screen before drawing |
| glClear( GL_COLOR_BUFFER_BIT ); |
| |
| typedef struct Vertex { |
| GLfloat x; |
| GLfloat y; |
| } Vertex; |
| |
| typedef struct Color { |
| GLubyte r; |
| GLubyte g; |
| GLubyte b; |
| GLubyte a; |
| } Color; |
| |
| typedef struct Type1 { |
| Vertex location; |
| Color color; |
| } Type1; |
| |
| typedef struct Type2 { |
| GLuint unused1; |
| Vertex location; |
| GLfloat unused2; |
| Color color; |
| } Type2; |
| |
| Type1 first[3] = { |
| {{-1.0, 0.0}, {0xFF, 0x00, 0x00, 0xFF}}, |
| {{ 0.0, 1.0}, {0x00, 0xFF, 0x00, 0xFF}}, |
| {{ 1.0, 0.0}, {0x00, 0x00, 0xFF, 0xFF}} |
| }; |
| |
| Type2 second[3] = { |
| {0.0, {-1.0, 0.0}, 0.0, {0xFF, 0x00, 0x00, 0xFF}}, |
| {0.0, { 1.0, 0.0}, 0.0, {0x00, 0x00, 0xFF, 0xFF}}, |
| {0.0, { 0.0, -1.0}, 0.0, {0x00, 0xFF, 0x00, 0xFF}}}; |
| |
| // make two vbo objects |
| GLuint vbo[2]; |
| glGenBuffers(2, &vbo[0]); |
| |
| // load the first into the context |
| glBindBuffer(GL_ARRAY_BUFFER, vbo[0]); |
| |
| // allocate enough space for 100 vertices |
| glBufferData(GL_ARRAY_BUFFER, sizeof(Type1)*100, NULL, GL_DYNAMIC_DRAW); |
| |
| // load the second into the context |
| glBindBuffer(GL_ARRAY_BUFFER, vbo[1]); |
| |
| // allocate enough space for 100 vertices |
| glBufferData(GL_ARRAY_BUFFER, sizeof(Type2)*100, NULL, GL_DYNAMIC_DRAW); |
| |
| // DRAW |
| |
| GLbyte * pointer; |
| |
| // Clear the screen before drawing |
| glClear( GL_COLOR_BUFFER_BIT ); |
| |
| glEnableClientState(GL_VERTEX_ARRAY); |
| glEnableClientState(GL_COLOR_ARRAY); |
| |
| // FIRST |
| // load the first into the context |
| glBindBuffer(GL_ARRAY_BUFFER, vbo[0]); |
| |
| // Load actual data in |
| glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(Type1)*3, &first[0]); |
| |
| // point to the buffer's location data |
| glVertexPointer(2, GL_FLOAT, sizeof(Type1), NULL); |
| |
| pointer = (GLbyte*)(((GLbyte*)&first[0].color) - ((GLbyte*)&first[0].location)); |
| |
| printf("location = %p\n", pointer); |
| // point to the buffer's color data |
| glColorPointer(4, GL_UNSIGNED_BYTE, sizeof(Type1), pointer); |
| |
| glDrawArrays(GL_TRIANGLE_STRIP, 0, 3); |
| |
| // SECOND |
| |
| // load the first into the context |
| glBindBuffer(GL_ARRAY_BUFFER, vbo[1]); |
| |
| // Load actual data in |
| glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(Type2)*3, &second[0]); |
| |
| pointer = (GLbyte*)((GLbyte*)&second[0].location - (GLbyte*)&second[0].unused1); |
| |
| // point to the buffer's location data |
| printf("location = %p\n", pointer); |
| glVertexPointer(2, GL_FLOAT, sizeof(Type2), pointer); |
| |
| pointer = (GLbyte*)((GLbyte*)&second[0].color - (GLbyte*)&second[0].unused1); |
| |
| // point to the buffer's location data |
| printf("location = %p\n", pointer); |
| glColorPointer(4, GL_UNSIGNED_BYTE, sizeof(Type2), pointer); |
| |
| glDrawArrays(GL_TRIANGLE_STRIP, 0, 3); |
| |
| glDisableClientState(GL_COLOR_ARRAY); |
| glDisableClientState(GL_VERTEX_ARRAY); |
| |
| for(int i = 0; i <= 2; ++ i) |
| { |
| SDL_GL_SetSwapInterval(i); |
| assert(SDL_GL_GetSwapInterval() == i); |
| } |
| |
| SDL_GL_SwapBuffers(); |
| |
| #ifndef __EMSCRIPTEN__ |
| // Wait for 3 seconds to give us a chance to see the image |
| SDL_Delay(3000); |
| #endif |
| |
| SDL_Quit(); |
| |
| return 0; |
| } |