Steward

分享是一種喜悅、更是一種幸福

程式語言 - Simple DirectMedia Layer (SDL) - v1.2 - C/C++ - OpenGL 1.0 - Apply Alpha Blending

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參考資訊：
https://github.com/gamedev-net/nehe-opengl

main.c

#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <SDL.h>
#include <GL/gl.h>
 
int main(int argc, char *argv[])
{
    const int W = 320;
    const int H = 240;
    GLuint tex = 0;
    GLdouble nearPlane = 0.1;
    GLdouble farPlane = 100.0;
    GLdouble top = nearPlane * tan(45.0 * 3.14159 / 360.0);
    GLdouble right = top * ((GLfloat)W / (GLfloat)H);
    SDL_Surface *bmp = NULL;
    SDL_Surface *screen = NULL;
  
    SDL_Init(SDL_INIT_VIDEO);
    screen = SDL_SetVideoMode(W, H, 16, SDL_SWSURFACE | SDL_OPENGL);
    bmp = SDL_LoadBMP("main.bmp");

    glGenTextures(1, &tex);
    glBindTexture(GL_TEXTURE_2D, tex);
    glEnable(GL_TEXTURE_2D);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, bmp->w, bmp->h, 0, GL_BGR, GL_UNSIGNED_BYTE, bmp->pixels);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

    GLfloat LightAmbient[] = {0.1f, 0.1f, 0.1f, 1.0f};
    GLfloat LightDiffuse[] = {1.0f, 1.0f, 1.0f, 1.0f};
    GLfloat LightPosition[] = {3.0f, 3.0f, 3.0f, 1.0f};

    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT1);

    glLightfv(GL_LIGHT1, GL_AMBIENT, LightAmbient);
    glLightfv(GL_LIGHT1, GL_DIFFUSE, LightDiffuse);
    glLightfv(GL_LIGHT1, GL_POSITION, LightPosition);

    glEnable(GL_COLOR_MATERIAL);
    glColorMaterial(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE);
  
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE);
    glColor4f(1.0f, 1.0f, 1.0f, 0.5f);

    glViewport(0, 0, W, H);
    glMatrixMode(GL_PROJECTION);
    glFrustum(-right, right, -top, top, nearPlane, farPlane); 
    glMatrixMode(GL_MODELVIEW);

    glLoadIdentity();
    glTranslatef(0.0f, 0.0f, -5.0f);
    glRotatef(45, 0.0f, 1.0f, 0.0f);
    glBindTexture(GL_TEXTURE_2D, tex);
    glBegin(GL_QUADS);
        glNormal3f(0.0f, 0.0f, 1.0f);
        glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f, -1.0f, 1.0f);
        glTexCoord2f(1.0f, 1.0f); glVertex3f(1.0f, -1.0f, 1.0f);
        glTexCoord2f(1.0f, 0.0f); glVertex3f(1.0f, 1.0f, 1.0f);
        glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, 1.0f, 1.0f);

        glNormal3f(0.0f, 0.0f, -1.0f);
        glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f, -1.0f);
        glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f, 1.0f, -1.0f);
        glTexCoord2f(1.0f, 1.0f); glVertex3f(1.0f, 1.0f, -1.0f);
        glTexCoord2f(1.0f, 0.0f); glVertex3f(1.0f, -1.0f, -1.0f);

        glNormal3f(0.0f, 1.0f, 0.0f);
        glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f, 1.0f, -1.0f);
        glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, 1.0f, 1.0f);
        glTexCoord2f(0.0f, 0.0f); glVertex3f(1.0f, 1.0f, 1.0f);
        glTexCoord2f(0.0f, 1.0f); glVertex3f(1.0f, 1.0f, -1.0f);

        glNormal3f(0.0f, -1.0f, 0.0f);
        glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f, -1.0f, -1.0f);
        glTexCoord2f(1.0f, 1.0f); glVertex3f(1.0f, -1.0f, -1.0f);
        glTexCoord2f(1.0f, 0.0f); glVertex3f(1.0f, -1.0f, 1.0f);
        glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f, 1.0f);

        glNormal3f(1.0f, 0.0f, 0.0f);
        glTexCoord2f(0.0f, 0.0f); glVertex3f(1.0f, -1.0f, -1.0f);
        glTexCoord2f(0.0f, 1.0f); glVertex3f(1.0f, 1.0f, -1.0f);
        glTexCoord2f(1.0f, 1.0f); glVertex3f(1.0f, 1.0f, 1.0f);
        glTexCoord2f(1.0f, 0.0f); glVertex3f(1.0f, -1.0f, 1.0f);

        glNormal3f(-1.0f, 0.0f, 0.0f);
        glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f, -1.0f);
        glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f, 1.0f);
        glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f, 1.0f, 1.0f);
        glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f, 1.0f, -1.0f);
    glEnd();

    glEnable(GL_BLEND);

    SDL_GL_SwapBuffers();
    SDL_Delay(3000);

    glDeleteTextures(1, &tex);

    SDL_FreeSurface(bmp);
    SDL_Quit();
    return 0;
}

編譯、執行

$ gcc main.c -I/usr/include/SDL -o main -lSDL -lGL
$ ./main