[Interest] Qt3D memory leaks

[william.crocker at analog.com]

On 04/13/2017 08:34 AM, Igor Mironchik wrote:
> Hi,
>
> Strange, I launch 3Dtree on Linux under valgrind:
>
> ==4321== HEAP SUMMARY:
> ==4321==     in use at exit: 439,965 bytes in 6,185 blocks
> ==4321==   total heap usage: 2,207,719 allocs, 2,201,534 frees, 1,241,469,509
> bytes allocated
> ==4321==
> ==4321== LEAK SUMMARY:
> ==4321==    definitely lost: 1,080 bytes in 10 blocks
> ==4321==    indirectly lost: 7,609 bytes in 55 blocks
> ==4321==      possibly lost: 416 bytes in 1 blocks
> ==4321==    still reachable: 430,860 bytes in 6,119 blocks
> ==4321==         suppressed: 0 bytes in 0 blocks
>

Check the virtual image size on Linux,
just to make sure it is not growing as well.
That is the bottom line.

> But on my Windows OS after each restart of tree I receive plus ~100MB additional
> memory.
>
> As I can see this memory still reachable. But why 3Dtree allocates more and more
> memory and doesn't use freed one?
>
> 13.04.2017 9:58, Sean Harmer пишет:
>> Hi,
>>
>> On 13/04/2017 07:09, Igor Mironchik wrote:
>>> Hello,
>>>
>>> 3Dtree has been updated. Now autumn is animated. Removed hand-made
>>> classes of leaf geometry and mesh. Now example uses ready mesh prepared
>>> in Blender. Modified a little constants of the tree. Example looks nice.
>>> This is a benchmark of your video card, because leafs and branches are
>>> stand alone objects (QEntity). For example 5 years tree has ~ 900
>>> objects. My Intel Pentium with Intel HD graphics normally paint only 5
>>> years tree, 6 years tree starts to slow down.
>>
>> Yes, at present each entity with a material/geometry renderer combo gets
>> translated to an OpenGL draw call. We are looking to add batching (similar to
>> how Qt Quick 2 works) but it's not there yet.
>>
>> If you don't need to address each individual leaf/branch in your object model.
>> E.g. if you're just rendering them, then you can get *much* better performance
>> by using instanced rendering.
>>
>> Essentially you have one entity representing all leaves. This entity contains
>> the material and geometry renderer as normal. The positions and any other
>> custom properties that vary between instances (rotation, leaf size, leaf
>> colour etc) should be placed into an additional attribute/buffer and provided
>> to the geometry renderer. On this attribute, set the divisor property to 1
>> meaning that 1 piece of data maps to 1 instance of the leave in the scene.
>> With this approach you will be able to render 10,000's leaves in a single draw
>> call. It maps through to a call to glDrawElementsInstanced() in case you want
>> to read up on it. Essentially you're moving the for loop over each leaf on to
>> the GPU.
>>
>> Typically, you'd have your data for the leaves in an array in C++ and use this
>> to populate the leaf instance buffer.
>>
>> The plan is to have a batcher that uses this instancing facility.
>>
>> Cheers,
>>
>> Sean
>>
>>>
>>> And one more - now you can rotate the tree with the left mouse button.
>>>
>>>
>>> 11.04.2017 12:15, Igor Mironchik пишет:
>>>>
>>>> Hi,
>>>>
>>>> I fixed a little 3Dtree. Now branches positions are correct. And I
>>>> know that not all leafs is visible (this is because leaf geometry is
>>>> implemented as plain which renders only on one side).
>>>>
>>>>
>>>> 10.04.2017 13:20, Igor Mironchik пишет:
>>>>>
>>>>> Hello,
>>>>>
>>>>> I guess that Qt3D has huge memory leaks.
>>>>>
>>>>> You can check it on this example: https://github.com/igormironchik/3Dtree
>>>>>
>>>>> It's 3D tree, that grows year by year.
>>>>>
>>>>> By default tree will grow 5 years (5 minutes).
>>>>>
>>>>> When tree grown you can restart tree. And here I delete all resources:
>>>>>
>>>>> void
>>>>>
>>>>> MainWindowPrivate::createTree()
>>>>> {
>>>>> if(m_tree)
>>>>> {
>>>>> for(constauto&e:m_rootEntity->childNodes())
>>>>> e->deleteLater();
>>>>> }
>>>>> m_tree=newBranch(m_startPos,m_endPos,c_startBranchRadius,
>>>>> true,m_rootEntity);
>>>>> m_tree->setAge(0.0f);
>>>>> m_tree->updatePosition();
>>>>> m_tree->placeLeafs();
>>>>> }
>>>>>
>>>>> But a lot of memory are eaten.
>>>>
>>>
>>>
>>>
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>>>
>>
>
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