Struggling with EXT_multisampled_render_to_texture on Mali-G76

Hi Ramil,

I notice you're using glRenderBufferStorageMultisample which is, confusingly, different to glRenderBufferStorageMultisampleEXT. I'd try switching to the EXT variant here and hopefully that helps.

Cheers,
Christian

Thanks for reply, I actually use glRenderBufferStorageMultisamleEXT, sorry, my bad, that's a typo.

Ah, OK. :) Did I interpret it right you're using pretty much the same code as in the spec example? I can try to repro on my side; in general I know this functionality works (as there are games relying on it) -- but wondering if some obscure things is causing an issue with that specific code. (Eg GL_UNSIGNED_SHORT_4_4_4_4 jumps out to me as 'not common' -- so could try something different there.)

I'll let you know what I find; please shout if your code is different to the spec example.

Thank you!
I've tried with GL_UNSIGNED_SHORT_4_4_4_4 when trying to do copy-paste from spec and GL_UNSIGNED_BYTE before that for our regular rgba8888 case.
Anothing thing that came to my mind: I'm using EGL with EGL_SAMPLES, 4 for main backbuffer which maybe also uses this extension.

If copy-pasted example from spec works fine for you - that will be very interesting to find out the truth! :)

I've tested the spec example on a few devices and drivers now, including a S10 with R19, but so far not been able to hit any problems (glCheckFramebufferStatus return GL_FRAMEBUFFER_COMPLETE). Is it possible to share a reproducer APK for this? Happy to have a look to try to debug what goes wrong.

Just for reference, here's a patch on top of the gles3jni example from https://github.com/android/ndk-samples (the same type of code works for the hello-gl2 sample as well) demonstrating how to load the right function pointers, plus how using the non-EXT glRenderbufferStorageMultisample can result in this error (see the #if for good vs non-working code):

diff --git a/gles3jni/app/src/main/cpp/RendererES3.cpp b/gles3jni/app/src/main/cpp/RendererES3.cpp
index df71a85..c7366a5 100644
--- a/gles3jni/app/src/main/cpp/RendererES3.cpp
+++ b/gles3jni/app/src/main/cpp/RendererES3.cpp
@@ -15,6 +15,8 @@
  */
 
 #include "gles3jni.h"
+#include <GLES2/gl2ext.h>
 #include <EGL/egl.h>
 
 #define STR(s) #s
@@ -117,6 +119,55 @@ bool RendererES3::init() {
     glVertexAttribPointer(OFFSET_ATTRIB, 2, GL_FLOAT, GL_FALSE, 2*sizeof(float), 0);
     glEnableVertexAttribArray(OFFSET_ATTRIB);
     glVertexAttribDivisor(OFFSET_ATTRIB, 1);
+#if 1
+       GLsizei width  = 256;
+       GLsizei height = 256;
+       GLint samples;
+       glGetIntegerv(GL_MAX_SAMPLES_EXT, &samples);
+
+    PFNGLRENDERBUFFERSTORAGEMULTISAMPLEEXTPROC glRenderbufferStorageMultisampleEXT =            (PFNGLRENDERBUFFERSTORAGEMULTISAMPLEEXTPROC)eglGetProcAddress("glRenderbufferStorageMultisampleEXT");
+    PFNGLFRAMEBUFFERTEXTURE2DMULTISAMPLEEXTPROC glFramebufferTexture2DMultisampleEXT =(PFNGLFRAMEBUFFERTEXTURE2DMULTISAMPLEEXTPROC)eglGetProcAddress("glFramebufferTexture2DMultisampleEXT");
+
+       /* Create multisampled depth renderbuffer */
+       GLuint depthbuffer;
+       glGenRenderbuffers(1, &depthbuffer);
+       glBindRenderbuffer(GL_RENDERBUFFER, depthbuffer);
+#if 0 // OK
+       glRenderbufferStorageMultisampleEXT(GL_RENDERBUFFER, samples, 
+               GL_DEPTH_COMPONENT16, width, height);
+#else // Fails
+       glRenderbufferStorageMultisample(GL_RENDERBUFFER, samples, 
+               GL_DEPTH_COMPONENT16, width, height);
+#endif
+       glBindRenderbuffer(GL_RENDERBUFFER, 0);
+
+       /* Create RGBA texture with single mipmap level */
+       GLuint texture;
+       glGenTextures(1, &texture);
+       glBindTexture(GL_TEXTURE_2D, texture);
+       glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, 
+               GL_UNSIGNED_SHORT_4_4_4_4, NULL);
+       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+       glBindTexture(GL_TEXTURE_2D, 0);
+
+       /* Create framebuffer object, attach texture and depth renderbuffer */
+       GLuint framebuffer;
+       glGenFramebuffers(1, &framebuffer);
+       glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
+       glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, 
+               GL_RENDERBUFFER, depthbuffer);
+       glFramebufferTexture2DMultisampleEXT(GL_FRAMEBUFFER, 
+               GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texture, 0, samples);
+
+       /* handle unsupported cases */
+       if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != 
+                       GL_FRAMEBUFFER_COMPLETE)
+       {
+        ALOGE("FBO incomplete: %x", glCheckFramebufferStatus(GL_FRAMEBUFFER));
+       } else ALOGE("FBO OK");
+
+    checkGlError("FBO");
+#endif
 
     ALOGV("Using OpenGL ES 3.0 renderer");
     return true;

It might be good to double-check any function pointer loader you might be using isn't grabbing the wrong function.

I'll check it and answer tomorrow.
Thank you a lot!

Hello.
I copy-pasted retrieving glRenderbufferStorageMultisampleEXT pointer as PFNGLRENDERBUFFERSTORAGEMULTISAMPLEEXTPROC into example and it fixes my issue.

The problem was in our engine macro GET_GL_FUNC(func_name, extSuffix) which first looks up function without suffix and only when it is not found looks up EXT version.

Thank you for help!

Super, thanks for confirming this was the issue! :)