242 строки
7.5 KiB
C
242 строки
7.5 KiB
C
/*******************************************************************
|
|
* *
|
|
* 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 1
|
|
#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>
|
|
|
|
void shaders() {
|
|
#if USE_GLEW
|
|
glewInit();
|
|
#endif
|
|
|
|
GLint ok;
|
|
|
|
const char *vertexShader = "void main(void) \n"
|
|
"{ \n"
|
|
" gl_Position = ftransform(); \n"
|
|
" gl_TexCoord[0] = gl_MultiTexCoord0; \n"
|
|
" gl_FrontColor = gl_Color; \n"
|
|
"} \n";
|
|
const char *fragmentShader = "uniform sampler2D tex0; \n"
|
|
"void main(void) \n"
|
|
"{ \n"
|
|
" gl_FragColor = gl_Color * texture2D(tex0, gl_TexCoord[0].xy); \n"
|
|
"} \n";
|
|
|
|
GLuint vs = glCreateShader(GL_VERTEX_SHADER);
|
|
glShaderSource(vs, 1, &vertexShader, NULL);
|
|
glCompileShader(vs);
|
|
glGetShaderiv(vs, GL_COMPILE_STATUS, &ok);
|
|
assert(ok);
|
|
|
|
GLuint fs = glCreateShader(GL_FRAGMENT_SHADER);
|
|
glShaderSource(fs, 1, &fragmentShader, NULL);
|
|
glCompileShader(fs);
|
|
glGetShaderiv(fs, GL_COMPILE_STATUS, &ok);
|
|
assert(ok);
|
|
|
|
GLuint program = glCreateProgram();
|
|
|
|
glAttachShader(program, vs);
|
|
glAttachShader(program, fs);
|
|
glLinkProgram(program);
|
|
glGetProgramiv(program, GL_LINK_STATUS, &ok);
|
|
assert(ok);
|
|
assert(glIsProgram(program));
|
|
assert(!glIsProgram(0));
|
|
assert(!glIsProgram(program+1)); // a number that can't be a real shader
|
|
|
|
glUseProgram(program);
|
|
|
|
{
|
|
// Also, check getting the error log
|
|
const char *fakeVertexShader = "atbute ve4 blarg; ### AAA\n";
|
|
GLuint vs = glCreateShader(GL_VERTEX_SHADER);
|
|
glShaderSource(vs, 1, &fakeVertexShader, NULL);
|
|
glCompileShader(vs);
|
|
glGetShaderiv(vs, GL_COMPILE_STATUS, &ok);
|
|
assert(!ok);
|
|
GLint infoLen = 0;
|
|
glGetShaderiv(vs, GL_INFO_LOG_LENGTH, &infoLen);
|
|
assert(infoLen > 1);
|
|
}
|
|
}
|
|
|
|
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_PROJECTION );
|
|
GLfloat matrixData[] = { 2.0/640, 0, 0, 0,
|
|
0, -2.0/480, 0, 0,
|
|
0, 0, -1, 0,
|
|
-1, 1, 0, 1 };
|
|
glLoadMatrixf(matrixData); // test loadmatrix
|
|
|
|
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 = IMG_Load("screenshot.png")) ) {
|
|
|
|
// 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\n");
|
|
}
|
|
|
|
// 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\n");
|
|
}
|
|
|
|
// 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 );
|
|
|
|
//SDL_LockSurface(surface);
|
|
|
|
// Add some greyness
|
|
memset(surface->pixels, 0x66, surface->w*surface->h);
|
|
|
|
// Edit the texture object's image data using the information SDL_Surface gives us
|
|
glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA, surface->w, surface->h, 0,
|
|
GL_RGBA, GL_UNSIGNED_BYTE, surface->pixels );
|
|
|
|
//SDL_UnlockSurface(surface);
|
|
}
|
|
else {
|
|
printf("SDL could not load image.bmp: %s\n", 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 );
|
|
|
|
shaders();
|
|
|
|
// Bind the texture to which subsequent calls refer to
|
|
glBindTexture( GL_TEXTURE_2D, texture );
|
|
|
|
// Use clientside vertex pointers to render two items
|
|
GLfloat vertexData[] = { 0, 0, 10, 10, // texture2, position2
|
|
1, 0, 300, 10,
|
|
1, 1, 300, 128,
|
|
0, 1, 10, 128,
|
|
0, 0.5, 410, 10,
|
|
1, 0.5, 600, 10,
|
|
1, 1, 630, 200,
|
|
0.5, 1, 310, 250,
|
|
0, 0, 100, 300,
|
|
1, 0, 300, 300,
|
|
1, 1, 300, 400,
|
|
0, 1, 100, 400 };
|
|
|
|
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
|
|
glTexCoordPointer(2, GL_FLOAT, 4*4, &vertexData[0]);
|
|
glEnableClientState(GL_VERTEX_ARRAY);
|
|
glVertexPointer(2, GL_FLOAT, 4*4, &vertexData[2]);
|
|
|
|
glDrawArrays(GL_QUADS, 0, 4);
|
|
|
|
glTexCoordPointer(2, GL_FLOAT, 4*4*2, &vertexData[0]); // and now with a different stride
|
|
glVertexPointer(2, GL_FLOAT, 4*4*2, &vertexData[2]);
|
|
glDrawArrays(GL_QUADS, 4, 4);
|
|
|
|
glTexCoordPointer(2, GL_FLOAT, 4*4, &vertexData[0]); // and back
|
|
glVertexPointer(2, GL_FLOAT, 4*4, &vertexData[2]);
|
|
glDrawArrays(GL_QUADS, 8, 4);
|
|
|
|
glDisableClientState(GL_TEXTURE_COORD_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
|
|
|
|
// Now we can delete the OpenGL texture and close down SDL
|
|
glDeleteTextures( 1, &texture );
|
|
|
|
SDL_Quit();
|
|
|
|
return 0;
|
|
}
|