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#include "SDL.h"
#include "SDL_opengl.h"
#include <stdio.h>
#include <string.h>
#define WIDTH 640
#define HEIGHT 480
int main(int argc, char* argv[]) {
SDL_Window* window;
SDL_GLContext context;
int i, j;
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
window = SDL_CreateWindow(
"OpenGL Window", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, WIDTH, HEIGHT, SDL_WINDOW_OPENGL);
if (!window) {
fprintf(stderr, "Couldn't create window: %s\n", SDL_GetError());
return 0;
}
context = SDL_GL_CreateContext(window);
if (!context) {
fprintf(stderr, "Couldn't create context: %s\n", SDL_GetError());
return 0;
}
glMatrixMode(GL_PROJECTION);
glOrtho(0.0, 8.0, 0.0, 3.0, -1.0, 1.0);
glMatrixMode(GL_MODELVIEW);
glClearColor(0, 0, 0, 1);
glEnable(GL_TEXTURE_2D);
GLuint texture;
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
GLubyte texture_data[] = {
0xffu, 0xffu, 0xffu, 0xffu,
0xffu, 0xffu, 0xffu, 0xeeu,
0xffu, 0xffu, 0xffu, 0xddu,
0xffu, 0xffu, 0xffu, 0xccu,
0xffu, 0xffu, 0xffu, 0xbbu,
0xffu, 0xffu, 0xffu, 0xaau,
0xffu, 0xffu, 0xffu, 0x99u,
0xffu, 0xffu, 0xffu, 0x88u,
0xffu, 0xffu, 0xffu, 0x77u,
0xffu, 0xffu, 0xffu, 0x66u,
0xffu, 0xffu, 0xffu, 0x55u,
0xffu, 0xffu, 0xffu, 0x44u,
0xffu, 0xffu, 0xffu, 0x33u,
0xffu, 0xffu, 0xffu, 0x22u,
0xffu, 0xffu, 0xffu, 0x11u,
0xffu, 0xffu, 0xffu, 0x00u,
};
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 2, 8, 0, GL_RGBA, GL_UNSIGNED_BYTE, texture_data);
const GLfloat vertex_data[4][4] = {
{ 0.25f, 0.25f, 0.0f, 0.0f },
{ 0.75f, 0.25f, 1.0f, 0.0f },
{ 0.25f, 0.75f, 0.0f, 1.0f },
{ 0.75f, 0.75f, 1.0f, 1.0f }
};
const GLushort indices[] = {
0u, 1u, 2u, 2u, 1u, 3u,
};
const GLenum alpha_test_modes[8] = {
GL_NEVER, GL_LESS, GL_LEQUAL, GL_EQUAL,
GL_NOTEQUAL, GL_GEQUAL, GL_GREATER, GL_ALWAYS
};
glVertexPointer(2, GL_FLOAT, sizeof (vertex_data[0]), &vertex_data[0][0]);
glEnableClientState(GL_VERTEX_ARRAY);
glTexCoordPointer(2, GL_FLOAT, sizeof (vertex_data[0]), &vertex_data[0][2]);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glEnable(GL_BLEND);
glEnable(GL_ALPHA_TEST);
glClear(GL_COLOR_BUFFER_BIT);
for(i = 0; i < 8; i++) {
for(j = 0; j < 3; j++) {
glLoadIdentity();
glTranslatef(i, j, 0.0f);
glAlphaFunc(alpha_test_modes[i], ((float)j)/2.0f );
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, indices);
}
}
SDL_GL_SwapWindow(window);
glDeleteTextures(1, &texture);
// Don't quit - we need to reftest the canvas! SDL_Quit();
return 0;
}
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