How to update FRAME_BUFFER texture size dynamically

[FuXiii]

I try to use osg::camera::attach(...) to implement post-process. All examples in osg , size of the texture attach for COLOR_BUFFER is fixed. If I resize my Viewer I need to resize the texture size which I had attached. If I directly resize it in update it doesn't work.

// in one of camera preDrawCallback
osg::ref_pte<osg::Texture2D> color_buffer;
void operator()(osg::RenderInfo& renderInfo) const override
{
      ...
      double current_viewer_width = ...//Get current viewer windows width
      double current_viewer_height = ...//Get current viewer windows height
      color_buffer->setTextureSize(current_viewer_width, current_viewer_height );

      // color_buffer->dirtyTextureObject(); // I try to dirty this texture, but it doesn't work.
}

How to resize the COLOR_BUFFER texture size dynamically?

[robertosfield]

I don't recall the details as it's over 5 years since I worked on the OSG, but GPUs don't like changing sizes of resources, they work best when you allocate a texture/framebuffer etc. at a fixed size for the life of the application. If you want to change the size you need to reallocate that resource. The is the same for OpenGL/OpenSceneGraph as it is for Vulkan/VulkanSceneGraph.

In the case of "resizing" textures the most efficient route is to allocate to the largest size you need then if you don't need to whole extents use a smaller a viewport to it, and adjust the texgen/texcoords when reference it.

[FuXiii]

Use a large FBO and just use smaller viewport, looks very interesting, good idea, I will try it. (｡•̀ᴗ-)✧

[xarray]

Have a look at osgverse (https://github.com/xarray/osgverse).
It supports FBO size updating when you resize the window. All work are done in struct MyResizedCallback, in pipeline/Pipeline.cpp.

[FuXiii]

Is this Pipeline.cpp:550 line code resize the FBO size? I had not found any code about resize the Texture which attached in RTT camera, is that means just resize the osg::GraphicsContext::Traits will synchronous update the FBO size?

By the way, two Chinese speak English, which is a bit strange.✧*｡ (ˊᗜˋ*) ✧*

王锐大佬您好~哈哈

[xarray]

camera->resizeAttachments() should do the trick, as I remember.

PS: yes we can speak Chinese in wechat groups or somewhere else, but not suitable in a public issue. :)

[FuXiii]

I tried this method, it fixed my issue. Thanks~( ๑╹ ꇴ╹) ｸﾞｯ!