Switching to committed resources

posted in Lyost's Journal
Published December 30, 2016
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Just a minor update from my previous post. I've updated my D3D12 framework (d3d12_framework.zip) to use committed instead of placed resources, along with centralizing the texture creation code. The switch over was pretty straight forward since it was basically removing an additional resource heap and switching my calls from CreateResource on my heap wrapper class (which internally called CreatePlacedResource) to use CreateCommittedResource instead while being careful to copy the correct initial state for the resource type. Since placed resources are something I will probably want to revisit down the road, along with revising them to allow for overlapping resources which is their primary benefit, I saved off the diff for reference code in ref directory in the project.

Also, in my previous post I had mentioned that I needed to use 2 different resources and copying between them for using a render target as a texture. While that is true with placed resources on heap tier 1 devices, when using committed resources it is possible to use the same resource for the render target as the texture. It just requires that the flags in the resource description includes D3D12_RESOURCE_FLAG_ALLOW_RENDER_TARGET. Since MSDN recommends setting that flag only when the texture will be used as a render target and since most textures will be loaded from a file in real usage instead, I created the additional Texture2DRenderTarget and D3D12_Texture2DRenderTarget classes. The existing RenderTarget/D3D12_RenderTarget class can have an instance created from one of these new classes which causes it to share the same resource (with corresponding AddRef/Release calls for managing its lifetime). I could have re-used the existing Texture2D/D3D12_Texture2D classes by adding a flag to their create functions, however adding the new classes keeps with the goal of using compile time type checking to avoid incorrect operations. I have added another test program to demonstrate this (render_target_to_texture_same_resource). In the spirit of the test programs being unit tests and for reference code, I have kept the previous test program and framework functionality around.

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