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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>
#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 Color {
GLubyte r;
GLubyte g;
GLubyte b;
GLubyte a;
} Color;
typedef struct Vertex {
GLfloat x;
GLfloat y;
Color color;
} Vertex;
Vertex vertices[18] = {
{-1.00, 0.0, {0xFF, 0x00, 0xFF, 0xFF}},
{-1.00, 1.0, {0xFF, 0xFF, 0x00, 0xFF}},
{-0.75, 0.0, {0xFF, 0x00, 0x00, 0xFF}},
{-0.75, 1.0, {0xFF, 0xFF, 0xFF, 0xFF}},
{-0.50, 0.0, {0xFF, 0x00, 0x00, 0xFF}},
{-0.50, 1.0, {0xFF, 0xFF, 0x00, 0xFF}},
{-0.25, 0.0, {0xFF, 0x00, 0xFF, 0xFF}},
{-0.25, 1.0, {0xFF, 0xFF, 0x00, 0xFF}},
{-0.00, 0.0, {0xFF, 0x00, 0x00, 0xFF}},
{-0.00, 1.0, {0xFF, 0xFF, 0xFF, 0xFF}},
{ 0.25, 0.0, {0xFF, 0x00, 0x00, 0xFF}},
{ 0.25, 1.0, {0xFF, 0xFF, 0x00, 0xFF}},
{ 0.50, 0.0, {0xFF, 0x00, 0xFF, 0xFF}},
{ 0.50, 1.0, {0xFF, 0xFF, 0x00, 0xFF}},
{ 0.75, 0.0, {0xFF, 0x00, 0x00, 0xFF}},
{ 0.75, 1.0, {0xFF, 0xFF, 0xFF, 0xFF}},
{ 1.00, 0.0, {0xFF, 0x00, 0x00, 0xFF}},
{ 1.00, 1.0, {0xFF, 0xFF, 0x00, 0xFF}}
};
Vertex vertices2[18] = {
{-1.00, -1.0, {0xFF, 0x00, 0xFF, 0xFF}},
{-1.00, 0.0, {0xFF, 0xFF, 0x00, 0xFF}},
{-0.75, -1.0, {0xFF, 0x00, 0x00, 0xFF}},
{-0.75, 0.0, {0xFF, 0xFF, 0xFF, 0xFF}},
{-0.50, -1.0, {0xFF, 0x00, 0x00, 0xFF}},
{-0.50, 0.0, {0xFF, 0xFF, 0x00, 0xFF}},
{-0.25, -1.0, {0xFF, 0x00, 0xFF, 0xFF}},
{-0.25, 0.0, {0xFF, 0xFF, 0x00, 0xFF}},
{-0.00, -1.0, {0xFF, 0x00, 0x00, 0xFF}},
{-0.00, 0.0, {0xFF, 0xFF, 0xFF, 0xFF}},
{ 0.25, -1.0, {0xFF, 0x00, 0x00, 0xFF}},
{ 0.25, 0.0, {0xFF, 0xFF, 0x00, 0xFF}},
{ 0.50, -1.0, {0xFF, 0x00, 0xFF, 0xFF}},
{ 0.50, 0.0, {0xFF, 0xFF, 0x00, 0xFF}},
{ 0.75, -1.0, {0xFF, 0x00, 0x00, 0xFF}},
{ 0.75, 0.0, {0xFF, 0xFF, 0xFF, 0xFF}},
{ 1.00, -1.0, {0xFF, 0x00, 0x00, 0xFF}},
{ 1.00, 0.0, {0xFF, 0xFF, 0x00, 0xFF}}
};
// make a vertex buffer for the second set of vertices
GLuint vbo = 0;
glGenBuffers(1, &vbo);
// bind to it
glBindBuffer(GL_ARRAY_BUFFER, vbo);
// send it to gl
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices2), vertices2, GL_STATIC_READ); // GL_STATIC_READ is not in WebGL!
// unbind from it
glBindBuffer(GL_ARRAY_BUFFER, 0);
// DRAW
// Clear the screen before drawing
glClear( GL_COLOR_BUFFER_BIT );
// This test ensures that we can use two separate arrays in memory for different
// attributes, and that they each can have different stride.
// The first test shows implicit striding (the zero indicates tightly packed)
// The second test shows explicit striding where the stride is passed in
// even though it also is tightly packed
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_COLOR_ARRAY);
// TEST 1 - clientside data
glVertexPointer(2, GL_FLOAT, sizeof(Vertex), vertices);
glColorPointer(4, GL_UNSIGNED_BYTE, sizeof(Vertex), &vertices[0].color);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 6);
glDrawArrays(GL_TRIANGLE_STRIP, 10, 3);
// TEST 2 - bind to array buffer, gl*Pointer calls are offsets into the buffer, which was previously uploaded to
glBindBuffer(GL_ARRAY_BUFFER, vbo);
glVertexPointer(2, GL_FLOAT, sizeof(Vertex), 0);
glColorPointer(4, GL_UNSIGNED_BYTE, sizeof(Vertex), (GLvoid*)((GLvoid*)&vertices2[0].color - (GLvoid*)&vertices2[0]));
// gldrawarrays first with a low number of vertices, then with a high number
glDrawArrays(GL_TRIANGLE_STRIP, 0, 6);
glDrawArrays(GL_TRIANGLE_STRIP, 10, 3);
glBindBuffer(GL_ARRAY_BUFFER, 0);
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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