New GLTF API Sample Base Class & GLTF Sample

[HaoranXu-ARM]

Description

Add a new GLTF API Sample base class to the framework, as well as a new GLTF sample instance to demonstrate its usage.

Note

We made the following changes to the framework:

• Added new sample base class containing helper functions for loading and rendering a glTF scene.

Fixes #848

The sample builds and runs successfully on Windows (NVIDIA) and Android (Mali).

General Checklist:

Please ensure the following points are checked:

• My code follows the coding style
• I have reviewed file licenses
• I have commented any added functions (in line with Doxygen)
• I have commented any code that could be hard to understand
• My changes do not add any new compiler warnings
• My changes do not add any new validation layer errors or warnings
• I have used existing framework/helper functions where possible
• My changes do not add any regressions
• I have tested every sample to ensure everything runs correctly
• This PR describes the scope and expected impact of the changes I am making

Note: The Samples CI runs a number of checks including:

• I have updated the header Copyright to reflect the current year (CI build will fail if Copyright is out of date)
• My changes build on Windows, Linux, macOS and Android. Otherwise I have documented any exceptions

If this PR contains framework changes:

• I did a full batch run using the batch command line argument to make sure all samples still work properly

Sample Checklist

If your PR contains a new or modified sample, these further checks must be carried out in addition to the General Checklist:

• I have tested the sample on at least one compliant Vulkan implementation
• If the sample is vendor-specific, I have tagged it appropriately
• I have stated on what implementation the sample has been tested so that others can test on different implementations and platforms
• Any dependent assets have been merged and published in downstream modules
• For new samples, I have added a paragraph with a summary to the appropriate chapter in the readme of the folder that the sample belongs to e.g. api samples readme
• For new samples, I have added a tutorial README.md file to guide users through what they need to know to implement code using this feature. For example, see conditional_rendering
• For new samples, I have added a link to the Antora navigation so that the sample will be listed at the Vulkan documentation site

[CLAassistant]

All committers have signed the CLA.

[asuessenbach]

I think, having some GLTFApiVulkanSample base class would be a good extension to the class hierarchy.
But the responsibilities between GLTFApiVulkanSample and GLTF seems to be a bit fuzzy:

• empty virtual functions introduced with GLTFApiVulkanSample, but only called in GLTF?
• elements (like present.pipeline.pipeline) that are members in GLTFApiVulkanSample, but created and used in GLTF; and destroyed in GLTFApiVulkanSample.
  Maybe more, stopped reviewing at that point.

If we want to have something like GLTFApiVulkanSample, the tasks and responsibilities of that class should be a bit cleaner.
Or maybe we could introduce some GLTF class that provides all those capabilities and could be used by a sample, without introducing another layer above ApiVulkanSample? Would probably make such a class more widely usable.

[HaoranXu-ARM]

• elements (like present.pipeline.pipeline) that are members in GLTFApiVulkanSample, but created and used in GLTF; and destroyed in GLTFApiVulkanSample.
  Maybe more, stopped reviewing at that point.

Fixed the mismatch in site of creation and destroy.

If we want to have something like GLTFApiVulkanSample, the tasks and responsibilities of that class should be a bit cleaner. Or maybe we could introduce some GLTF class that provides all those capabilities and could be used by a sample, without introducing another layer above ApiVulkanSample? Would probably make such a class more widely usable.

I think the goal of GLTFApiVulkanSample is to provide a basic framework for rendering a glTF scene, but leave the application-specific methods such as pipeline creation to the individual samples. GLTF is directly created from the sample template that comes with this PR, which builds upon it by filling the gaps with a very simple application set-up.

The expected use case will be that developers use the generate.py script to generate a working sample that loads & renders a glTF scene straight out-of-the-box, and they can start from there by overriding the functionalities. So I think the additional layer above ApiVulkanSample is still useful in its own right.

[SaschaWillems]

Not sure about this. What we're looking for is an improved glTF loader class that adds stuff like animations. Adding another sample base class (we already have two) might not be the right direction.