将 IOSurface 支持的纹理转换为GL_TEXTURE_2D

Question

我想用mipmapping渲染一个IOSurface纹理。

我正在从这样的IOSurface生成OpenGL纹理：

let error = CGLTexImageIOSurface2D(context.cglContextObj!, 
GLenum(GL_TEXTURE_RECTANGLE_ARB),GLenum(GL_RGBA), GLsizei(width), GLsizei(height),
GLenum(GL_BGRA), GLenum(GL_UNSIGNED_INT_8_8_8_8_REV), surface!, 0)

并使用简单的片段着色器渲染它：

#version 120
uniform sampler2DRect texture;
varying vec2 texCoord;
uniform vec2 size;
void main(){
    vec4 tex = texture2DRect(texture, texCoord*size);
    gl_FragColor = tex;
}

这工作正常。但不幸的是，纹理没有被 mipmap，并且在以较小的尺寸查看时非常颗粒/像素化。经过进一步的研究，似乎IOSurface支持的纹理不仅仅限于GL_TEXTURE_RECTANGLE_ARB目标，而且不支持 mipmap。

好吧。所以我最好的选择似乎是：

1. 将GL_TEXTURE_RECTANGLE_ARB纹理复制到GL_TEXTURE_2D纹理
2. 为这个新纹理生成 mipmap

请注意，我是在不支持OpenGL 4.3的Mac上进行开发的，因此我无法使用此处方便glCopyImageSubData。相反，我将步骤 1 的方法基于这个答案：如何有效地将纹理 1 复制到纹理 2？

我的完整代码现在如下所示：

if !hasCreatedTexture {
    glGenTextures(1, &texture);
    glGenTextures(1, &arbTexture);
    glGenFramebuffers(1, &fbo)
    hasCreatedTexture = true
}
glEnable(GLenum(GL_TEXTURE_RECTANGLE_ARB))
glBindTexture(GLenum(GL_TEXTURE_RECTANGLE_ARB), arbTexture)
let error = CGLTexImageIOSurface2D(context.cglContextObj!, GLenum(GL_TEXTURE_RECTANGLE_ARB), GLenum(GL_RGBA), GLsizei(width), GLsizei(height), GLenum(GL_BGRA), GLenum(GL_UNSIGNED_INT_8_8_8_8_REV), surface!, 0)

glBindFramebuffer(GLenum(GL_FRAMEBUFFER), fbo);
glFramebufferTexture2D(GLenum(GL_READ_FRAMEBUFFER), GLenum(GL_COLOR_ATTACHMENT0),
                           GLenum(GL_TEXTURE_RECTANGLE_ARB), arbTexture, 0);
glFramebufferTexture2D(GLenum(GL_DRAW_FRAMEBUFFER), GLenum(GL_COLOR_ATTACHMENT1),
                           GLenum(GL_TEXTURE_2D), texture, 0);
glDrawBuffer(GLenum(GL_COLOR_ATTACHMENT1));
glBlitFramebuffer(0, 0, GLint(width), GLint(height), 0, 0, GLint(width), GLint(height), GLbitfield(GL_COLOR_BUFFER_BIT), GLenum(GL_NEAREST));
glBindTexture(GLenum(GL_TEXTURE_2D), texture)

我更改了着色器以支持GL_TEXTURE_2D：

#version 120
uniform sampler2D texture;
varying vec2 texCoord;
void main(){
    vec4 tex = texture2D(texture, texCoord);
    gl_FragColor = tex;
}

这就是我卡住的地方。图像全黑，我不知道为什么它不起作用。

我尝试像这样查看像素数据：

var pixelData = UnsafeMutablePointer<GLubyte>(allocatingCapacity: Int(width * height * 4))
glGetTexImage(GLenum(GL_TEXTURE_2D), 0, GLenum(GL_BGRA),
GLenum(GL_UNSIGNED_INT_8_8_8_8_REV), pixelData)
print(NSData(bytes: pixelData, length: 50000).description)

而且都是零。我的方法有问题，还是问题与处理IOSurface背纹理特别相关？

Answer 1

最后使用以下方法进行了这项工作：

func createMipTexture() {
    guard let surface = self.surface else { return }
    glBindTexture(GLenum(GL_TEXTURE_2D), texture);
    glEnable(GLenum(GL_TEXTURE_2D))
    guard let address = IOSurfaceGetBaseAddress(surface) as UnsafeMutableRawPointer? else { return }
    IOSurfaceLock(surface, .readOnly, nil)
    glTexImage2D(GLenum(GL_TEXTURE_2D), 0, GL_RGBA, GLsizei(width), GLsizei(height), 0,  GLenum(GL_BGRA), GLenum(GL_UNSIGNED_INT_8_8_8_8_REV), address)
    IOSurfaceUnlock(surface, .readOnly, nil);
    glTexParameteri(GLenum(GL_TEXTURE_2D), GLenum(GL_TEXTURE_MAX_LEVEL), 100)
    glHint(GLenum(GL_GENERATE_MIPMAP_HINT), GLenum(GL_NICEST));
    glGenerateMipmap(GLenum(GL_TEXTURE_2D))
    glTexParameteri(GLenum(GL_TEXTURE_2D), GLenum(GL_TEXTURE_WRAP_S), GL_REPEAT);
    glTexParameteri(GLenum(GL_TEXTURE_2D), GLenum(GL_TEXTURE_WRAP_T), GL_REPEAT);
    glTexParameteri(GLenum(GL_TEXTURE_2D), GLenum(GL_TEXTURE_MAG_FILTER), GL_LINEAR);
    glTexParameteri(GLenum(GL_TEXTURE_2D), GLenum(GL_TEXTURE_MIN_FILTER), GL_LINEAR_MIPMAP_LINEAR);
}