android - 在 android native 代码 (ndk) 中使用 OpenGL ES 2.0 FrameBuffer (FBO) 和 Stencil

Question

我正在尝试生成一个 frambuffer 对象并在使用 NDK (r5b) 的 native android 应用程序中使用模板。目标设备运行 froyo 2.2，支持 OpenGL ES 2.0。

所以，我一直在我的 c++ native 库中编写大量 gl 代码，除此之外没有解决任何问题。我似乎无法让它发挥作用。

这是创建帧缓冲区的代码 fragment 。完整性都很好，但屏幕仍然完全黑色。这就像我正在创建的 fbo 并没有真正绑定(bind)到由应用程序的 Java 部分创建的 gl 表面。我的应用程序代码的其余部分都很好，如果我删除 fbo 创建和绑定(bind)，一切都运行良好，除了我没有我的应用程序所需的模板。

    GLint backingWidth = 1024;
      GLint backingHeight = 1024;


    //Create the FrameBuffer and binds it
    glGenFramebuffers(1, &_defaultFramebuffer);
    checkGlError("glGenFramebuffers");
    glBindFramebuffer(GL_FRAMEBUFFER, _defaultFramebuffer);
    checkGlError("glBindFramebuffer");

    //Create the RenderBuffer for offscreen rendering // Color
    glGenRenderbuffers(1, &_colorRenderbuffer);
    checkGlError("glGenRenderbuffers color");
    glBindRenderbuffer(GL_RENDERBUFFER, _colorRenderbuffer);
    checkGlError("glBindRenderbuffer color");
    glRenderbufferStorage(GL_RENDERBUFFER, GL_RGBA4, backingWidth, backingHeight);
    checkGlError("glRenderbufferStorage color");

    //Create the RenderBuffer for offscreen rendering // Depth
    glGenRenderbuffers(1, &_depthRenderbuffer);
    checkGlError("glGenRenderbuffers depth");
    glBindRenderbuffer(GL_RENDERBUFFER, _depthRenderbuffer);
    checkGlError("glBindRenderbuffer depth");
    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, backingWidth, backingHeight);
    checkGlError("glRenderbufferStorage depth");

    //Create the RenderBuffer for offscreen rendering // Stencil
    glGenRenderbuffers(1, &_stencilRenderbuffer);
    checkGlError("glGenRenderbuffers stencil");
    glBindRenderbuffer(GL_RENDERBUFFER, _stencilRenderbuffer);
    checkGlError("glBindRenderbuffer stencil");
    glRenderbufferStorage(GL_RENDERBUFFER, GL_STENCIL_INDEX8, backingWidth, backingHeight);
    checkGlError("glRenderbufferStorage stencil");

    // bind renderbuffers to framebuffer object
    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, _depthRenderbuffer);
    checkGlError("glFramebufferRenderbuffer depth");
    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, _colorRenderbuffer);
    checkGlError("glFramebufferRenderbuffer color");
    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT, GL_RENDERBUFFER, _stencilRenderbuffer);
    checkGlError("glFramebufferRenderbuffer stencil");

//Test for FrameBuffer completeness
    GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
    checkGlError("glCheckFramebufferStatus");
    switch (status)
    {
    case GL_FRAMEBUFFER_COMPLETE: LOGI("\n\n\nFLIPBOOM : FBO complete  GL_FRAMEBUFFER_COMPLETE %x\n\n\n", status);break;

    case GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT: LOGI("\n\n\nFLIPBOOM : FBO GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT  %x\n\n\n", status);break;

    case GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT: LOGI("\n\n\nFLIPBOOM : FBO FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT  %x\n\n\n", status);break;

    case GL_FRAMEBUFFER_INCOMPLETE_DIMENSIONS: LOGI("\n\n\nFLIPBOOM : FBO FRAMEBUFFER_INCOMPLETE_DIMENSIONS  %x\n\n\n", status);break;

    case GL_FRAMEBUFFER_UNSUPPORTED: LOGI("\n\n\nFLIPBOOM : FBO GL_FRAMEBUFFER_UNSUPPORTED  %x\n\n\n", status);break;

    default : LOGI("\n\n\nFLIPBOOM : failed to make complete framebuffer object %x\n\n\n", status);
    }

我也尝试过渲染到 2D 纹理而不是渲染缓冲区...也没有用。

那么，有什么办法可以解决这个问题吗？我在这里弄错了吗？如果有人有任何想法，请让我知道……花了太多时间查找这个问题……呵呵 ;)

提前致谢!

干杯!

---

编辑:

好的，我已经设法使模板缓冲区工作，但 FBO 无法正常工作。我认为 Android 不完全支持 OpenGL ES 2.0(顺便说一句，这里使用 r5b)。我认为方法 stub 已定义，但未完全实现。或者创建的 GlSurfaceView 没有与 FBO 正确链接。

至于模板缓冲区，我不得不做

glEnable(GL_DEPTH_TEST);

并删除 glDepthMask 的使用，以便它们正常工作。

Answer 1

@Zennichimaro，关于模板缓冲区的使用!

初始化期间:

glBindFramebuffer(GL_FRAMEBUFFER, 0);
glEnable(GL_DEPTH_TEST);

渲染期间:

glViewport(0, 0, GetViewWidth(), GetViewHeight());
checkGlError("glViewport");

if (_firstRenderDone == false)
{
    glClearDepthf( 0.9f );
    glDepthMask( GL_TRUE );
    glClear( GL_DEPTH_BUFFER_BIT );
    glDepthMask( GL_FALSE );
    _firstRenderDone = true;
}

glClearColor(M_channelToFloat(_backgroundColor.r),
               M_channelToFloat(_backgroundColor.g),
               M_channelToFloat(_backgroundColor.b),
               M_channelToFloat(_backgroundColor.a));
checkGlError("glClearColor");
glClearStencil( 0 );
checkGlError("glClearStencil");
glClear( GL_COLOR_BUFFER_BIT | GL_STENCIL_BUFFER_BIT );
checkGlError("glClear");

_stencilLayer = 1;

//use our custom shaders
if( _program )
{
    glUseProgram(_program);


    if( transformMatrix3x3 != NULL )
    {
        glUniformMatrix3fv( _uniforms[OGL_UNIFORM_TRANSFORM], 1, false, transformMatrix3x3 );
    }

     // reset the shading.
    glUniform1f( _uniforms[ OGL_UNIFORM_SHADE ], 0.0f );
}


//Do the actual drawing (Triangle Slip)
 if( object )
  {
     _isRender = true;
    object->OglDraw(this);
    _isRender = false;
  }

当我需要使用模板时，我会根据需要使用以下方法:

void GlEs2Renderer::StencilStartMask()
{
if (!USE_STENCIL)   //For debugging purpose
    return;


glEnable(GL_STENCIL_TEST);

//Turn off writing to the Color Buffer and Depth Buffer
//We want to draw to the Stencil Buffer only
glColorMask( GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE );

//Set 1 into the stencil buffer
glStencilFunc( GL_ALWAYS, NewStencilLayer(), 0xFFFFFFFF );
glStencilOp( GL_ZERO, GL_ZERO, GL_REPLACE );
}

void GlEs2Renderer::StencilUseMask()
{
if (!USE_STENCIL)   //For debugging purpose
        return;

//Turn back on Color Buffer and Depth Buffer
glColorMask( GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE );

//Only write to the Stencil Buffer where 1 is set
glStencilFunc( GL_EQUAL, StencilLayer(), 0xFFFFFFFF);

//Keep the content of the Stencil Buffer
glStencilOp( GL_KEEP, GL_KEEP, GL_KEEP );
}

void GlEs2Renderer::StencilOverlayMask()
{
if (!USE_STENCIL)   //For debugging purpose
        return;

//Turn back on Color Buffer and Depth Buffer
glColorMask( GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE );
glDepthMask(true);

//Only write to the Stencil Buffer where 1 is set
glStencilFunc( GL_EQUAL, StencilLayer(), 0xFFFFFFFF);

//Keep the content of the Stencil Buffer and increase when z passed
glStencilOp(GL_KEEP, GL_KEEP, GL_INCR);
}

最后，我使用双 channel 技术在模板内部绘制...这是一个示例:

glVertexAttribPointer(OGL_ATTRIB_VERTEX, 2, GL_FLOAT, 0, 0, _triangles);
glEnableVertexAttribArray(OGL_ATTRIB_VERTEX);
glVertexAttribPointer(OGL_ATTRIB_COLOR, 4, GL_UNSIGNED_BYTE, 1, 0, _colors);
glEnableVertexAttribArray(OGL_ATTRIB_COLOR);

glContext->StencilStartMask();
glDrawArrays(GL_TRIANGLE_STRIP, 0, _nPoints);

glContext->StencilUseMask();;
glDrawArrays(GL_TRIANGLE_STRIP, 0, _nPoints);

glContext->StencilEndMask();

我的代码相当复杂，所以很难只发布与模板相关的内容，但我希望它会有所帮助；)