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我正在尝试将使用 SDL 1.2 和 OpenGL 1.3 的游戏移植到 Android 并最终移植到 iOS。

为此，我不得不切换到 SDL 1.3，下一个未发布的版本将成为 SDL 2.0，它已被移植到 Android。最初的结果很好，只有 SDL 和 SDL_image 一切正常。

但是当我将 OpenGL ES 1.1 添加到混合中并尝试渲染一个带纹理的矩形时，我得到的只是一个白色矩形。

有什么想法我在这里做错了吗？就像我说的，只是 SDL/SDL_image 显示图像就好了。

编辑：我已经根据下面 Ryan Maloney 的建议更新了下面的代码，即在我使用 GL_FLOAT 的地方使用浮点文字并尝试使用SDL_GL_BindTexture而不是手动创建纹理。但是也不起作用，我得到一个黑色纹理和一些错误：没有可用的 EGL 配置，EGLNativeWindowType 0x2a1b5380 已经连接到另一个 API。glBindTexture仍然会产生白色纹理。

编辑2：刚刚有了实际检查错误的绝妙想法：如果我glGetError()在之后打电话glTexImage2D，我会得到GL_INVALID_OPERATION。

#include <GLES/gl.h>
#include <SDL.h>
#include <SDL_image.h>
#include <string>

// Set to 1 to use SDL_GL_BindTexture instead of glBindTexture
#define USE_SDL_TEXTURE 0

static const int screen_width = 640;
static const int screen_height = 480;

void init_opengl()
{
    glEnable(GL_TEXTURE_2D);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    glEnable(GL_BLEND);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glViewport(0, 0, screen_width, screen_height);
    glOrthof(0, screen_width, screen_height, 0, -1, 1);
    glMatrixMode(GL_MODELVIEW);
}

int next_power_of_two(int n)
{
    double logbase2 = log((double) n) / log(2.0);
    return (int) (pow(2, ceil(logbase2)) + 0.5);
}

SDL_Surface* convert_to_power_of_two(SDL_Surface* surface)
{
    int width = next_power_of_two(surface->w);
    int height = next_power_of_two(surface->h);

    SDL_Surface* pot_surface = SDL_CreateRGBSurface(0, width, height, 32,
                                                    0x00ff0000, 0x0000ff00,
                                                    0x000000ff, 0xff000000);
    SDL_Rect dstrect;
    dstrect.w = surface->w;
    dstrect.h = surface->h;
    dstrect.x = 0;
    dstrect.y = 0;
    SDL_SetSurfaceAlphaMod(surface, 0);
    SDL_BlitSurface(surface, NULL, pot_surface, &dstrect);
    SDL_FreeSurface(surface);

    return pot_surface;
}

GLenum get_texture_format(SDL_PixelFormat* pixel_format, GLint bpp)
{
    switch (bpp) {
    case 4:
        return GL_RGBA;
    case 3:
        return GL_RGB;
    }
    throw "Unsupported pixel format";
}

#if USE_SDL_TEXTURE
SDL_Texture* load_image(const std::string& path, SDL_Renderer* renderer)
#else
GLuint load_image(const std::string& path)
#endif
{
    SDL_Surface* surface = IMG_Load(path.c_str());
    SDL_Surface* pot_surface = convert_to_power_of_two(surface);

#if USE_SDL_TEXTURE
    return SDL_CreateTextureFromSurface(renderer, surface);
#else
    SDL_PixelFormat* pixel_format = pot_surface->format;
    GLint bpp = pixel_format->BytesPerPixel;
    GLenum texture_format = get_texture_format(pixel_format, bpp);

    GLuint texture;
    glGenTextures(1, &texture);
    glBindTexture(GL_TEXTURE_2D, texture);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexImage2D(GL_TEXTURE_2D, 0, bpp, pot_surface->w, pot_surface->h, 0,
                 texture_format, GL_UNSIGNED_BYTE, pot_surface->pixels);

    SDL_FreeSurface(pot_surface);
    return texture;
#endif
}

#if USE_SDL_TEXTURE
void draw_texture(SDL_Texture* texture, float width, float height)
#else
void draw_texture(GLuint texture, float width, float height)
#endif
{
#if USE_SDL_TEXTURE
    SDL_GL_BindTexture(texture, NULL, NULL);
#else
    glBindTexture(GL_TEXTURE_2D, texture);
#endif

    GLfloat texture_coordinates[] = {0.0f, 1.0f,
                                     0.0f, 0.0f,
                                     1.0f, 1.0f,
                                     1.0f, 0.0f};
    glTexCoordPointer(2, GL_FLOAT, 0, texture_coordinates);
    glEnableClientState(GL_TEXTURE_COORD_ARRAY);

    GLfloat vertices[] = {0.0f, height,
                          0.0f, 0.0f,
                          width, height,
                          width, 0.0f};
    glVertexPointer(2, GL_FLOAT, 0, vertices);
    glEnableClientState(GL_VERTEX_ARRAY);

    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

    glDisableClientState(GL_VERTEX_ARRAY);
    glDisableClientState(GL_TEXTURE_COORD_ARRAY);
}

int main(int argc, char* argv[])
{
SDL_Init(SDL_INIT_VIDEO);
atexit(SDL_Quit);

IMG_Init(IMG_INIT_PNG);
atexit(IMG_Quit);

SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);

const Uint32 flags = SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN;
SDL_Window* window = SDL_CreateWindow("Foo", 0, 0,
                                      screen_width, screen_height, flags);

#if USE_SDL_TEXTURE
SDL_Renderer* renderer = SDL_CreateRenderer(window, 1, SDL_RENDERER_ACCELERATED);
#endif

SDL_GLContext context = SDL_GL_CreateContext(window);
SDL_GL_SetSwapInterval(1);

init_opengl();

#if USE_SDL_TEXTURE
    SDL_Texture* texture = load_image("character_editor_bg.png", renderer);
#else
    GLuint texture = load_image("character_editor_bg.png");
#endif

SDL_Event event;
for (;;) {
    SDL_WaitEvent(&event);
    if (event.type == SDL_QUIT)
        break;

    glClear(GL_COLOR_BUFFER_BIT);
    draw_texture(texture, screen_width, screen_height);

    SDL_GL_SwapWindow(window);
    SDL_Delay(1);
}

SDL_GL_DeleteContext(context);
SDL_DestroyWindow(window);
SDL_Quit();
return 0;
}
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1 回答 1

2

终于发现问题了。事实上，我glTexImage2D完全错误地使用了它，并且由于某种原因它在 OpenGL 1.3 中运行良好。

这是调用应该是什么：

    glTexImage2D(GL_TEXTURE_2D, 0, texture_format, pot_surface->w, pot_surface->h, 0,
             texture_format, GL_UNSIGNED_BYTE, pot_surface->pixels);

以前，我bpp作为第三个参数传递，这是垃圾。

于 2012-12-29T07:09:03.860 回答