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/*******************************************************************
* *
* 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);
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;
}
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