I was trying to use FBO and PBO together, read pixels from FBO to PBO, everyframe.
Codes are below:
//at the beginning:
//fbo
glGenFramebuffers(1, &m_fBO);
glBindFramebuffer(GL_FRAMEBUFFER, m_fBO);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texid, 0);
//pbo
glGenBuffersARB(1, &m_pbo);
glBindBufferARB(GL_PIXEL_PACK_BUFFER_ARB, m_pbo);
glBufferDataARB(GL_PIXEL_PACK_BUFFER_ARB, DATA_SIZE, 0, GL_STREAM_READ_ARB);
//at each frame:
glBindFramebuffer(GL_FRAMEBUFFER, m_fBO);
Draw_some_stuff();
glBindBufferARB(GL_PIXEL_PACK_BUFFER_ARB, m_pbo);
glReadBuffer(GL_COLOR_ATTACHMENT0_EXT);
glPixelStorei(GL_PACK_ALIGNMENT, 1);
glReadPixels(0, 0, m_width, m_height, GL_RGBA, GL_UNSIGNED_BYTE, 0); //err occurs
Ptr = glMapBufferARB(GL_PIXEL_PACK_BUFFER_ARB, GL_READ_ONLY_ARB);
Cpu_works_on_Ptr();
glUnmapBufferARB(GL_PIXEL_PACK_BUFFER_ARB);
It works fine on PC. But failed to running on my android phone, got an error 0x0502(GL_INVALID_OPERATION) right after glReadPixels.
I believe my codes are the same as the bottom answer at this link:
Reading the pixels values from the Frame Buffer Object (FBO) using Pixel Buffer Object (PBO)
Has anyone got a clue? Where did I do it wrong?
Related
Given a textureId, I need to extract pixel data from the texture.
glReadPixels works, but it is extremely slow on some devices, even with FBO/PBO. (On Xiaomi MI 5, it is 65 ms, and even slower with PBO). So I decided to use Hardwarebuffer and eglImageKHR, which should be much faster. However, I cannot get it to work. The screen goes black, and nothing is read into the data.
//attach inputTexture to FBO
glBindFrameBuffer(GL_FRAMEBUFFER, fbo)
glFrameBufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, textureId, 0)
//allocate hardware buffer
AHardwareBuffer* buffer = nullptr;
AHardwareBuffer_Desc desc = {};
desc.width = width;
desc.height = height;
desc.layers = 1;
desc.usage = AHARDWAREBUFFER_USAGE_CPU_READ_OFTEN | AHARDWAREBUFFER_USAGE_CPU_WRITE_NEVER
| AHARDWAREBUFFER_USAGE_GPU_COLOR_OUTPUT ;
desc.format = AHARDWAREBUFFER_FORMAT_R8G8B8A8_UNORM;
//create eglImageKHR
EGLint eglAttributes[] = {EGL_IMAGE_PRESERVED_KHR, EGL_TRUE, EGL_NONE};
EGLClientBuffer clientBuffer = eglGetNativeClientBufferANDROID(buffer);
EGLImageKHR eglImageKhr = eglCreateImageKHR(eglDisplay, eglContext,
EGL_NATIVE_BUFFER_ANDROID, clientBuffer, eglAttributes);
//read pixels to hardware buffer ????
glBindTexture(GL_TEXTURE_2D, textureId);
glEGLImageTargetTexture2DOES(GL_TEXTURE_2D, eglImageKhr);
//copy pixels into memory
void *readPtr;
AHardwareBuffer_lock(buffer, AHARDWAREBUFFER_USAGE_CPU_READ_OFTEN, -1, nullptr, (void**)&readPtr);
memcpy(writePtr, readPtr, width * 4);
AHardwareBuffer_unlock(buffer, nullptr);
This is my code with glReadPixels, and it just can get the pixels after attaching the texture to framebuffer.
GLES30.glBindFramebuffer(GLES30.GL_FRAMEBUFFER, fboBuffer!![0])
GLES30.glFramebufferTexture2D(GLES30.GL_FRAMEBUFFER,
GLES30.GL_COLOR_ATTACHMENT0,
GLES30.GL_TEXTURE_2D,
inputTextureId,
0)
GLES30.glReadPixels(0, 0, width, height, GLES30.GL_RGBA, GLES30.GL_UNSIGNED_BYTE, byteBuffer)
Please tell me where I did wrong :(
//read pixels to hardware buffer ????
glBindTexture(GL_TEXTURE_2D, textureId);
glEGLImageTargetTexture2DOES(GL_TEXTURE_2D, eglImageKhr);
This doesn't do any reading of data. This is just setting up the texture to refer to the EGLImage. If you want data to be copied into it you need to either do glCopyTexImage2D() or bind it to a framebuffer and render in to it.
I've got some C code to render some OpenGL stuff and it's running on both Android and iOS. On Android it looks fine. But on iOS it is flipped vertically.
Here's some simple code to demonstrate (only copied the relevant parts because OpenGL C code is long-winded):
GLfloat vVertices[] = {
0.0f, 0.5f,
-0.5f, -0.5f,
0.5f, -0.5f
};
glViewport(0, 0, context->width, context->height);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glUseProgram(data->programObject);
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, vVertices);
glEnableVertexAttribArray(0);
glDrawArrays(GL_TRIANGLES, 0, 3);
glDisableVertexAttribArray(0);
On Android it looks like this:
But on iOS it looks like this:
The only thing that differs between the two platforms is the initialization code for OpenGL ES, since all the OpenGL code is shared C code. However, I can't spot anything obviously wrong with the init code.
Here's the init code (I removed most error handling because there are no errors being triggered apart from the one I left in):
- (void)initGL {
_context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES3];
[EAGLContext setCurrentContext:_context];
[self createCVBufferWithSize:_renderSize withRenderTarget:&_target withTextureOut:&_texture];
glBindTexture(CVOpenGLESTextureGetTarget(_texture), CVOpenGLESTextureGetName(_texture));
glTexImage2D(GL_TEXTURE_2D, // target
0, // level
GL_RGBA, // internalformat
_renderSize.width, // width
_renderSize.height, // height
0, // border
GL_RGBA, // format
GL_UNSIGNED_BYTE, // type
NULL); // data
// HACK: we always get an "error" here (GL_INVALID_OPERATION) despite everything working. See https://stackoverflow.com/questions/57104033/why-is-glteximage2d-returning-gl-invalid-operation-on-ios
glGetError();
glGenRenderbuffers(1, &_depthBuffer);
glBindRenderbuffer(GL_RENDERBUFFER, _depthBuffer);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, _renderSize.width, _renderSize.height);
glGenFramebuffers(1, &_frameBuffer);
glBindFramebuffer(GL_FRAMEBUFFER, _frameBuffer);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, CVOpenGLESTextureGetName(_texture), 0);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, _depthBuffer);
if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) {
NSLog(#"failed to make complete framebuffer object %x", glCheckFramebufferStatus(GL_FRAMEBUFFER));
} else {
NSLog(#"Successfully initialized GL");
char* glRendererName = getGlRendererName();
char* glVersion = getGlVersion();
char* glShadingLanguageVersion = getGlShadingLanguageVersion();
NSLog(#"OpenGL renderer name: %s, version: %s, shading language version: %s", glRendererName, glVersion, glShadingLanguageVersion);
}
}
And here's the code that creates the actual texture (using EAGL):
- (void)createCVBufferWithSize:(CGSize)size
withRenderTarget:(CVPixelBufferRef *)target
withTextureOut:(CVOpenGLESTextureRef *)texture {
CVReturn err = CVOpenGLESTextureCacheCreate(kCFAllocatorDefault, NULL, _context, NULL, &_textureCache);
if (err) return;
CFDictionaryRef empty;
CFMutableDictionaryRef attrs;
empty = CFDictionaryCreate(kCFAllocatorDefault,
NULL,
NULL,
0,
&kCFTypeDictionaryKeyCallBacks,
&kCFTypeDictionaryValueCallBacks);
attrs = CFDictionaryCreateMutable(kCFAllocatorDefault, 1,
&kCFTypeDictionaryKeyCallBacks,
&kCFTypeDictionaryValueCallBacks);
CFDictionarySetValue(attrs, kCVPixelBufferIOSurfacePropertiesKey, empty);
CVPixelBufferCreate(kCFAllocatorDefault, size.width, size.height,
kCVPixelFormatType_32BGRA, attrs, target);
CVOpenGLESTextureCacheCreateTextureFromImage(kCFAllocatorDefault,
_textureCache,
*target,
NULL, // texture attributes
GL_TEXTURE_2D,
GL_RGBA, // opengl format
size.width,
size.height,
GL_BGRA, // native iOS format
GL_UNSIGNED_BYTE,
0,
texture);
CFRelease(empty);
CFRelease(attrs);
}
Can anyone tell me why iOS is flipped like this? I've since noticed other people with the same problem, such as here but haven't found a solution yet.
On each draw frame when I bind an FBO am I supposed to call
GLES20.glFramebufferTexture2D(GLES20.GL_FRAMEBUFFER,
GLES20.GL_COLOR_ATTACHMENT0, GLES20.GL_TEXTURE_2D,
ResourceManager.windowTex[0], 0);
Are you only supposed to call this when you initialize your framebuffer or every frame? It doesn't draw for me unless I call it after glBindFramebuffer.
The attachment bindings are part of the FBO state. You only need to call glFramebufferTexture2D() once, while the FBO is bound. Those same textures will still be attached when you later bind the same FBO again.
One possible trap is that the texture object must have been created before it can be attached to an FBO. Generating the name alone is not enough, it needs to be bound at least once to create the actual texture object. For example, the following would be an error:
GLuint texId = 0;
glGenTextures(1, &texId);
GLuint fboId = 0;
glGenFramebuffers(1, &fboId);
glFramebufferTexture2D(GL_FRAMEBUFFER,
GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texId, 0);
glBindTexture(GL_TEXTURE_2D, texId);
glTexImage2D(...);
The texture object was not created in this case before being attached to the FBO. The following on the other hand is valid:
GLuint texId = 0;
glGenTextures(1, &texId);
glBindTexture(GL_TEXTURE_2D, texId);
glBindTexture(GL_TEXTURE_2D, 0);
GLuint fboId = 0;
glGenFramebuffers(1, &fboId);
glFramebufferTexture2D(GL_FRAMEBUFFER,
GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texId, 0);
glBindTexture(GL_TEXTURE_2D, texId);
glTexImage2D(...);
Note that the texture does not have to be currently bound when glFramebufferTexture2D() is called, and it's also not necessary for texture data to have been specified at that point. It just needs to have been bound at least once to trigger creation of the texture object.
I am doing off-screen processing using opengl es2.0 on Android.
I created a renderbuffer, and attached it to a framebuffer FBO, after rendering to the FBO, I try to get the pixels from that FBO by getReadPixels() method. But I got nothing.
The code is shown below:
GLuint resultFBO;// FBO
GLuint rboId; //render buffer id
glGenRenderbuffers(1, &rboId);
glBindRenderbuffer(GL_RENDERBUFFER, rboId);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, image_width, image_height);
glBindRenderbuffer(GL_RENDERBUFFER, 0);
glGenFramebuffers(1, &resultFBO);
glBindFramebuffer(GL_FRAMEBUFFER, resultFBO);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT,
GL_RENDERBUFFER, rboId);
glBindFramebuffer(GL_FRAMEBUFFER, 0);
GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
if (status == GL_FRAMEBUFFER_COMPLETE) {
//LOGH("Single FBO setup successfully.");
} else {
LOGH("Problem in setup FBO texture: %d .", status);
}
//After render to the FBO
glBindFramebuffer(GL_FRAMEBUFFER, resultFBO);
glReadPixels(0, 0, w, h, GL_DEPTH_COMPONENT, GL_UNSIGNED_BYTE, imageSetData);
You can not glReadPixels() from GL_DEPTH_COMPONENT in OpenGL ES 2.0. Only from the color buffer. See API Reference here.
void glReadPixels( GLint x,
GLint y,
GLsizei width,
GLsizei height,
GLenum format,
GLenum type,
GLvoid * data);
format
Specifies the format of the pixel data. The following symbolic values are accepted: GL_ALPHA, GL_RGB, and GL_RGBA
Workaround1: If precision is not that important, you can write depth to one of the 8bit color channels instead.
Workaround2: You can write depth into the RGBA channels by packing the float into a vec4: See for example this SO thread.
Workaround3: You can try the OES_depth_texture extension and, if supported, render to a depth texture instead.
I am trying to generate a frambuffer object and use stencil inside a native android application using the NDK (r5b). Target device is running froyo 2.2, supporting OpenGL ES 2.0.
So, I've been coding lots of gl code in my c++ native libs and havent got through any problem except for this. I just can't seems to make it work.
Here's a code snipplet for the framebuffer creation. Completness is all good, but screen remains completly black. It's like the fbo I am creating is not really bound to the gl surface that is created by the Java part of the app. The rest of my app code is all good, if I remove the fbo creation and binding, everything works perfectly fine except that I don't have the stencils working which I need for my app.
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);
}
I've also tried rendering to a 2D texture instead of the renderbuffer...didn't worked either.
So, Is there a way I can fix this ? Am I getting something wrong here ? If anyone has any ideas please lemme know....been spending way too much time looking up this problem...hehe ;)
Thanks in advance !
Cheers !
EDIT :
Ok, I've manage to make the stencil buffer work but the FBO are just not working. I think OpenGL ES 2.0 is not fully supported by android (using r5b here btw). I think method stubs are defined, but not fully implemented. Or the GlSurfaceView created doesn't link correctly with the FBOs.
As for the stencil buffer, I had to do
glEnable(GL_DEPTH_TEST);
and remove the usage of glDepthMask in order for them to work correctly.
# Zennichimaro, For the stencil buffer usage !
During Initialisation :
glBindFramebuffer(GL_FRAMEBUFFER, 0);
glEnable(GL_DEPTH_TEST);
During the rendering :
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;
}
When I need to use stencil I use the following methods depending on what I need :
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);
}
And Finally I do the double pass technic to draw inside the stencil ... Here's an example :
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();
My code is fairly complex so it's hard to only post what's related to the stencil, But I hope It'll help ;)