Using OpenGL ES 2.0 FrameBuffer (FBO) and Stencil in android Native code (ndk)
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.
Answer
@ 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 ;)