3d scene does not show lines and texts compared with osg

[rhabacker]

Describe the error Loading the file attached to vsg-dev/VulkanSceneGraph#308 with vsgviewer, you can see drawing problems on the right side in the attached screenshot. Lines and texts are not displayed.

Reproduce Steps to reproduce the behavior:

1. checkout git repo from vsg-dev/vsgFramework unter src
2. run

cmake -B ~/src/vsgFramework-build -S ~/src/vsgFramework -DBUILD_OpenSceneGraph=1 -DBUILD_SHARED_LIBS=1
cmake --build ~/src/vsgFramework-build

3. unpack the zip file attached to vsg-dev/VulkanSceneGraph#308 in ~/src
4. run LD_LIBRARY_PATH=~/src/vsgFramework-build/lib64 VSG_FILE_PATH=~/src/vsgFramework-build/src/vsgExamples/data ~/src/vsgFramework-build/bin/vsgviewer ~/src/demo.osgt.
5. see error

Expected behavior The viewer should display the lines and texts as they are shown in the reference image created with osgviewer on the left.

Screenshots

Desktop (please fill in the following information):

• Operating system: openSUSE Linux
• version 15.2

Additional context

• Vulkan 1.2.189 has been installed
• Moved this bug from VulkanSceneGraph according to https://github.com/vsg-dev/VulkanSceneGraph/issues/385#issuecomment-999484599

[rhabacker]

Robert Osfield wrote at https://github.com/vsg-dev/VulkanSceneGraph/issues/385#issuecomment-999484599

The vsgXchange OSG loaders doesn't yet support lines or text.

[rhabacker]

Robert Osfield wrote at vsg-dev/VulkanSceneGraph#385 (comment)

The vsgXchange OSG loaders doesn't yet support lines or text.

Here is a simplified test case for lines test-lines.osgt.zip which looks with osgviewer as

[rhabacker]

After a look into the vsg examples I saw the method vsg::Builder::createCylinder() which can possibly be used to create lines.

[rhabacker]

After a look into the vsg examples I saw the method vsg::Builder::createCylinder() which can possibly be used to create lines.

Since Vulkan supports drawing lines directly (see the wireframe property in the vsg::StateInfo class), an alternative approach is to draw lines directly. A proposal for a reference implementation for adding a line was submitted with https://github.com/vsg-dev/VulkanSceneGraph/pull/666. Since the proposal has proven to be inefficient, an improvement is needed. A corresponding discussion thread for will be opened next week.

[robertosfield]

Drawing lines is essentially the same as drawing points and triangle meshes, and for most cases would be done just by creating the state, vertex arrays and primitives required.

vsg::Builder at present isn't a general purpose geometry building tool, but one written to create specific primitive shapes like spheres, boxes etc. It's a different usage case to what is required for mapping osg::Geometry with lines & points to VSG, the closest would usage case would be mapping osg::ShapeDrawable to the VSG.