如何在 1D 缓冲区中生成 2D 纹理并将其加载到 OpenGL 中？

Question

在某些情况下，我以一维二进制数据和指定格式的形式从相机获取实时图像数据。我想将此格式转换为 RGBA 或 BGRA 并使用它来纹理屏幕对齐的四边形。但是，我似乎误解了一些关于如何在 OpenGL 中生成和加载纹理的核心概念，因为我无法让以下示例正常工作：

void OpenGLRenderer::renderScreenAlignedQuad(const XrCompositionLayerProjectionView& view)
{
    CHECK_GL_ERROR(glBindVertexArray(m_screenAlignedQuad.vao));
    CHECK_GL_ERROR(glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_screenAlignedQuad.indexBuffer));

    // Update texture
    glPixelStorei(GL_UNPACK_ALIGNMENT, 4);
    glBindTexture(GL_TEXTURE_2D, m_screenAlignedQuad.texture);

#define BUFF_HEIGHT 1152
#define BUFF_WIDTH 1152
    unsigned char *buffer = new unsigned char[BUFF_HEIGHT * BUFF_WIDTH * 4];
    for (int32_t y = 0; y < BUFF_HEIGHT; y++) {
        for (int32_t x = 0; x < BUFF_WIDTH; x++) {
            int32_t ind = y * BUFF_WIDTH + x * 4;
            buffer[ind] = 255;   // R
            buffer[ind + 1] = 0; // G
            buffer[ind + 2] = 0; // B
            buffer[ind + 3] = 255; // A
        }
    }
    {// =! Critical section !=
        // The mutex will be unlocked when this object goes out of scope;
        // Note that it blocks other threads from writing, but allows reading
        std::shared_lock<std::shared_mutex> sl(m_videoStreamContext.g_currentFrameDataMutex);
        CHECK_GL_ERROR(glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, BUFF_HEIGHT, BUFF_WIDTH, 0, GL_RGBA, GL_UNSIGNED_BYTE, buffer));
    }// =! Critical section !=

    CHECK_GL_ERROR(glDrawElements(GL_TRIANGLES, m_screenAlignedQuad.indexCount, GL_UNSIGNED_SHORT, 0));
}

我想在这里实现的是将整个屏幕变成红色的纹理。相反，我得到了这个：

纹理坐标似乎没问题（我之前能够正确地纹理加载的图像）：

对于更多调试信息，我添加了更多颜色：

void OpenGLRenderer::renderScreenAlignedQuad(const XrCompositionLayerProjectionView& view)
{
    CHECK_GL_ERROR(glBindVertexArray(m_screenAlignedQuad.vao));
    CHECK_GL_ERROR(glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_screenAlignedQuad.indexBuffer));

    // Update texture
    glPixelStorei(GL_UNPACK_ALIGNMENT, 4);
    glBindTexture(GL_TEXTURE_2D, m_screenAlignedQuad.texture);

    unsigned char *buffer = new unsigned char[BUFF_HEIGHT * BUFF_WIDTH * 4];
    for (int32_t y = 0; y < BUFF_HEIGHT; y++) {
        for (int32_t x = 0; x < BUFF_WIDTH; x=x+4) {
            int32_t ind = y * BUFF_WIDTH + x;
                if (y < BUFF_HEIGHT / 2) {
                    buffer[ind] = 255;   // R
                    buffer[ind + 1] = 0; // G
                    buffer[ind + 2] = 0; // B
                    buffer[ind + 3] = 255; // A
                } else if (x < BUFF_WIDTH / 2) {
                    buffer[ind] = 0;   // R
                    buffer[ind + 1] = 0; // G
                    buffer[ind + 2] = 255; // B
                    buffer[ind + 3] = 255; // A
                } else {
                    buffer[ind] = 0;   // R
                    buffer[ind + 1] = 255; // G
                    buffer[ind + 2] = 0; // B
                    buffer[ind + 3] = 255; // A
                }
        }
    }

    {// =! Critical section !=
        // The mutex will be unlocked when this object goes out of scope;
        // Note that it blocks other threads from writing, but allows reading
        std::shared_lock<std::shared_mutex> sl(m_videoStreamContext.g_currentFrameDataMutex);
        CHECK_GL_ERROR(glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, BUFF_HEIGHT, BUFF_WIDTH, 0, GL_RGBA, GL_UNSIGNED_BYTE, buffer));
    }// =! Critical section !=

    CHECK_GL_ERROR(glDrawElements(GL_TRIANGLES, m_screenAlignedQuad.indexCount, GL_UNSIGNED_SHORT, 0));
    delete buffer;
}

输出如下所示：

所以看起来纹理在两个方向上都被渲染得太小了。纹理上的环绕设置设置为钳位，因此不应像以前那样重复。我在这里做错了什么？

编辑：只要不影响程序的正确性，请忽略任何明显的低效率或丑陋的代码结构。我正在尝试让最简单的版本暂时可用。

Answer 1

您的 2d 到 1d 索引计算刚刚出错：

int32_t ind = y * BUFF_WIDTH + x * 4;

应该是这样的

int32_t ind = (y * BUFF_WIDTH + x) * 4;

您在第二种方法中也犯了同样的基本错误，只是混淆了一点：

for (int32_t y = 0; y < BUFF_HEIGHT; y++) {
     for (int32_t x = 0; x < BUFF_WIDTH; x=x+4) {
         int32_t ind = y * BUFF_WIDTH + x;

x 现在是 x * 4 之前的样子（但你的循环应该转到 x <= 4*BUFF_WIDTH），ind = y * 4 * BUFF_WIDTH + x 是正确的。