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Hi Philipp,<br>
<br>
I'm not sure, if I really understand what you intend to do.<br>
<br>
In my case my scene is very complex and I get timeouts on my graphic
card.<br>
So I do a rendering into many tiles, each holding a small portion of
the scene.<br>
Thus culling avoids transfer of the complete data onto the graphic
card.<br>
The tiles are assigned to a quadtree and rendered with paged LOD.<br>
<br>
Would that also be a solution for you?<br>
<br>
- Werner -<br>
<br>
<div class="moz-cite-prefix">Am 10.12.2019 um 16:42 schrieb Philipp
Wagner:<br>
</div>
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cite="mid:c6f7907d-6c89-4c00-973c-f9dc0585ae32@googlegroups.com">
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<div dir="ltr">Hi,<br>
<br>
I want to perform an offscreen rendering of a scene that is too
large to fit into the GPU memory at once (lots of big textures).<br>
My idea was to render parts of the scene each in its own frame,
and disable the clearing of the depth and color buffer.<br>
This does work for the color buffer, but the depth buffer seems
to be cleared after each frame, which leads to incorrect results
(The later parts are drawn over the previous ones, even though
they are behind the other parts).<br>
<br>
The algorithm:<br>
1. Create camera/context/...<br>
2. Clear the buffers (i.e. Render an empty scene with a clear
mask of (GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT)<br>
3. Disable buffer clearing<br>
4. Render each part in its own frame<br>
a. Add part to the scene<br>
b. Render<br>
c. Remove part from the scene<br>
5. Read back color buffer<br>
<br>
<br>
osg::ref_ptr<::osg::Camera> camera = new osg::Camera();<br>
<br>
//Here we set the camera orientation/projection matrix<br>
<br>
camera->setClearColor(...);<br>
camera->setGraphicsContext(context);<br>
<br>
osg::ref_ptr<osg::Image> img = new osg::Image;<br>
img->allocateImage(textureWidth, textureHeight, 1, GL_RGBA,
GL_UNSIGNED_BYTE);<br>
camera->attach(osg::Camera::COLOR_BUFFER0, img, numSamples);<br>
camera->attach(osg::Camera::DEPTH_BUFFER,
GL_DEPTH_COMPONENT32);<br>
camera->setRenderOrder(osg::Camera::PRE_RENDER);<br>
camera->setRenderTargetImplementation(osg::Camera::RenderTargetImplementation::FRAME_BUFFER_OBJECT);<br>
camera->setReferenceFrame(osg::Camera::ABSOLUTE_RF);<br>
camera->setProjectionResizePolicy(osg::Camera::FIXED);<br>
camera->setViewport(0, 0, img->s(), img->t());<br>
viewer->addSlave(camera);<br>
<br>
camera->setClearMask(GL_DEPTH_BUFFER_BIT |
GL_COLOR_BUFFER_BIT);<br>
viewer->frame();<br>
camera->setClearMask(0);<br>
for (auto& item : parts)<br>
{<br>
//Here we create and add the item to the scene...<br>
viewer->frame();<br>
//Here we remove item from the scene and delete it<br>
}<br>
<div><br>
</div>
<div>Thanks in advance</div>
<div>Phil</div>
</div>
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