This would be a bug in the JNI code, which is responsible for protecting from the GC any and all memory which it is using. Only it can do so, because only it knows when it is done.
That's unlikely, though. The the JNI API makes it impossible to get your JNI code to get its hands on the data without protecting it from the GC -- and even then, you may only get a copy, if the system feels like doing that instead. Bugs ARE still possible -- you can free it an then hang onto the data you no longer have rights to. But really, the only impact of holding onto a buffer on the Java side, only to discard it next frame, is to make the GC work harder. If you were to REUSE that buffer, however, you'd avoiding extra GC work. On Feb 25, 12:45 am, Twisted Ware <[email protected]> wrote: > Robert has a very good point, but I also think you can expect the GL > implementation to allow the buffers to get garbage collected before > they have been used. > > You allocate the buffer in a scope and then pass that buffer pointer > into the GL system - and then toss the memory away. Unless you flush > the GL queue, there is no guarantee the graphics system has done > anything with the data you've passed. The point of the direct buffers > is to prevent copying data around all the time during these calls, so > the GL system could be using the memory directly much later than you > expect. You should probably not deallocate the buffer until the next > frame comes around, when you know the system is done with the data. > > On Feb 24, 2:50 pm, Robert Green <[email protected]> wrote: > > > > > The OpenGL wrappers take the data pointer passed in by those sorts of > > methods using native GetDirectBufferAddress of the corresponding type > > (int or float) and pass that pointer into the native gl method. That > > only works correctly if it's a direct buffer. > > > I just checked android_opengl_GLES10.cpp and GLES11.cpp and found that > > glTexImage2D and glBufferData use the same getPointer() method to get > > to the data. That means that behavior should be the same. > > Ultimately, the data comes from: > > > *array = (jarray) _env->CallStaticObjectMethod(nioAccessClass, > > getBaseArrayID, buffer); > > offset = _env->CallStaticIntMethod(nioAccessClass, > > getBaseArrayOffsetID, buffer); > > data = _env->GetPrimitiveArrayCritical(*array, (jboolean *) > > 0); > > return (void *) ((char *) data + offset); > > > then the gl method is called, then the pointer is released. > > > Always use direct buffers when working with any aspect of OpenGL on > > Android. > > > On Feb 24, 4:01 am, Clankrieger <[email protected]> wrote: > > > > As what I am aware of, VBOs do not need direct buffers (and indirect > > > buffers might be handled faster), but this is just a detail. I also > > > tried GL_FIXED but it did not make much difference for me. I assume > > > that it gives performance gains only if you have a) static data that > > > is converted to fixed format once and then re-rendered or b) do all > > > calculations with fixed number precision (which is making things a lot > > > more complicated and less readable when you need to update data). So I > > > switched back to Float because I hat to convert most values to fixed > > > before uploading them in GL calls. > > > > I wonder if your offsets are correct? Is _pos_size_bytes the correct > > > offset? For safety, I would stick to non-interleaved arrays for > > > testing. Also I'm not sure when to array-copying in the bufferdata > > > call takes place - have you tried a glFlush call or a buffer rebind > > > (bind VBO to 0 and the ID again) after all the buffering? Somebody > > > with knowledge about the native part of of this buffering could help > > > you better with this, I guess. > > > > T. > > > > On Feb 16, 8:43 pm, Viktor Linder <[email protected]> wrote: > > > > > As you say, the most likely explanation is that I have a bad pointer > > > > being used somewhere. The thing is I have gone over this code a bunch > > > > of times and tried lots of different checks and I just can't find > > > > what's wrong. > > > > Do you have any pointers on ways to debug the crash in the GL library? > > > > > I forgot to mention: I bind the array buffer to 0 after the call to > > > > glDrawElements(), so any future draw calls that are not using VBOs > > > > will not break. Also, I am not using VBOs for all draw calls. > > > > > You keep a different VBO for each channel; is using a single VBO for > > > > several channels not allowed? > > > > > If its possible to use a single buffer that would reduce the needed > > > > calls to glBindBuffer() and allowed interleaved data which would > > > > improve cache locality. > > > > > Curious; did using GL_FIXED give a large performance gain? > > > > > Thanks for your help. > > > > > /Viktor > > > > On 16 Feb, 21:25, Robert Green <[email protected]> wrote: > > > > > > You're probably pointing something to some bad memory location > > > > > somewhere. I know you didn't post all of your real code so I can't > > > > > really say for sure but it looks to me like you may be doing something > > > > > wrong with your buffers. Here's how I do it: > > > > > > -- Load -- > > > > > GL11 gl11 = (GL11) gl; > > > > > if (modelData.normals != null) { > > > > > int[] vboIds = new int[5]; > > > > > gl11.glGenBuffers(5, vboIds, 0); > > > > > vertexVBOId = vboIds[0]; > > > > > texVBOId = vboIds[1]; > > > > > normalVBOId = vboIds[2]; > > > > > indexVBOId = vboIds[3]; > > > > > lightmapVBOId = vboIds[4]; > > > > > } else { > > > > > int[] vboIds = new int[4]; > > > > > gl11.glGenBuffers(4, vboIds, 0); > > > > > vertexVBOId = vboIds[0]; > > > > > texVBOId = vboIds[1]; > > > > > indexVBOId = vboIds[2]; > > > > > lightmapVBOId = vboIds[3]; > > > > > } > > > > > gl11.glBindBuffer(GL11.GL_ARRAY_BUFFER, > > > > > vertexVBOId); > > > > > gl11.glBufferData(GL11.GL_ARRAY_BUFFER, > > > > > modelData.vertices.length * > > > > > 4, BufferUtil.createDirectIntBuffer(modelData.vertices), > > > > > GL11.GL_STATIC_DRAW); > > > > > gl11.glBindBuffer(GL11.GL_ARRAY_BUFFER, > > > > > texVBOId); > > > > > gl11.glBufferData(GL11.GL_ARRAY_BUFFER, > > > > > modelData.tex.length * 4, > > > > > BufferUtil.createDirectIntBuffer(modelData.tex), GL11.GL_STATIC_DRAW); > > > > > if (modelData.normals != null) { > > > > > > > > > > gl11.glBindBuffer(GL11.GL_ARRAY_BUFFER, normalVBOId); > > > > > > > > > > gl11.glBufferData(GL11.GL_ARRAY_BUFFER, modelData.normals.length * > > > > > 4, BufferUtil.createDirectIntBuffer(modelData.normals), > > > > > GL11.GL_STATIC_DRAW); > > > > > } > > > > > > > > > > gl11.glBindBuffer(GL11.GL_ELEMENT_ARRAY_BUFFER, indexVBOId); > > > > > > > > > > gl11.glBufferData(GL11.GL_ELEMENT_ARRAY_BUFFER, > > > > > modelData.indices.length * 2, > > > > > BufferUtil.createDirectShortBuffer(modelData.indices), > > > > > GL11.GL_STATIC_DRAW); > > > > > if (hasLightMap) { > > > > > > > > > > gl11.glBindBuffer(GL11.GL_ARRAY_BUFFER, lightmapVBOId); > > > > > > > > > > gl11.glBufferData(GL11.GL_ARRAY_BUFFER, > > > > > lightMapModelData.tex.length * 4, > > > > > BufferUtil.createDirectIntBuffer(lightMapModelData.tex), > > > > > GL11.GL_STATIC_DRAW); > > > > > } > > > > > BaseRenderer.checkErrors(gl11); > > > > > gl11.glBindBuffer(GL11.GL_ARRAY_BUFFER, 0); > > > > > > > > > > gl11.glBindBuffer(GL11.GL_ELEMENT_ARRAY_BUFFER, 0); > > > > > > -- Draw -- > > > > > > // use VBOs > > > > > gl11.glBindBuffer(GL11.GL_ARRAY_BUFFER, > > > > > vertexVBOId); > > > > > gl11.glVertexPointer(3, GL10.GL_FIXED, 0, 0); > > > > > if (modelData.normals != null) { > > > > > > > > > > gl11.glBindBuffer(GL11.GL_ARRAY_BUFFER, normalVBOId); > > > > > gl11.glNormalPointer(GL10.GL_FIXED, > > > > > 0, 0); > > > > > } > > > > > > > > > > gl11.glBindBuffer(GL11.GL_ARRAY_BUFFER, texVBOId); > > > > > gl11.glTexCoordPointer(2, > > > > > GL10.GL_FIXED, 0, 0); > > > > > > > > > > //gl11.glBindBuffer(GL11.GL_ELEMENT_ARRAY_BUFFER, indexVBOId); > > > > > // the main draw call > > > > > gl11.glDrawArrays(GL11.GL_TRIANGLES, 0, > > > > > vertexCount); > > > > > //gl11.glDrawElements(GL10.GL_TRIANGLES, > > > > > vertexCount, > > > > > GL10.GL_UNSIGNED_SHORT, 0); > > > > > // clean up > > > > > gl11.glBindBuffer(GL11.GL_ARRAY_BUFFER, 0); > > > > > > > > > > //gl11.glBindBuffer(GL11.GL_ELEMENT_ARRAY_BUFFER, 0); > > > > > > This code draws without indices but the commented code for indices is > > > > > there. > > > > > I use fixed point coordinates for verts, normals and UVs. You'd want > > > > > to change that to floats for what you're doing. > > > > > > On Feb 16, 1:42 pm, Viktor Linder <[email protected]> wrote: > > > > > > > I am having trouble with implementing VBOs for my game. > > > > > > I get crashes at random when calling glDrawElements() directly after > > > > > > glGenBuffers() / glBufferData(). > > > > > > The crashes disappear when I add printouts which leads me to believe > > > > > > it might be a race condition between glBufferData() and > > > > > > glDrawElements() of some sort. > > > > > > Or I am doing something else that breaks it, but I can't see what. > > > > > > > Here's what I do: > > > > > > > ...... > > read more » -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
