Direct3D can perform a lot of different operations. We use \u201ccapability\u201d or \u201ccap\u201d to describe what the library can do. Direct3D 12 has a single API, ID3D12Device::CheckFeatureSupport<\/a>, which tells us whether a cap is supported and its level of support in the runtime environment. Here’s the function signature:<\/p>\n To make use of this API, you must provide a D3D12_FEATURE enum to identify the feature group you’re querying. You must also provide a pointer to one of the D3D12_FEATURE_DATA_* data structures specific to that feature and its size.<\/p>\n You may find this API hard to use for the following reasons:<\/p>\n To improve your experience with feature checking, we have added a wrapper API with a simpler call routine and more friendly interface. Actually, it\u2019s not a single API but an entire class. Allow me to introduce the new \u201cCD3DX12FeatureSupport\u201d class, located in d3dx12.h<\/a> and available from the DirectX-Headers repo on GitHub<\/a>.<\/p>\n It\u2019s hard to explain why this class is better the original API. Let\u2019s first walk through two examples.<\/p>\n In the first example, we\u2019d like to check three different caps: \u201cROVs Supported\u201d, \u201cWave Ops\u201d, and Raytracing Tier. With the old API, we must figure out which features include these three caps. After looking up from the documentation, we found that they come from three different feature groups: D3D12_OPTIONS, D3D12_OPTIONS1, and D3D12_OPTIONS5. This is bad news since we\u2019ll need to create three separate \u201cD3D12_FEATURE_DATA\u201d structs. What\u2019s worse, it\u2019s very easy to mistake one feature for another because all three have similar names. The final code looks like this:<\/p>\n Also notice that the API calls above are not safe. If this code is running on a very old version of D3D12 runtime, some of these checks may fail and the data fields may be invalid. You should enclose the \u201cCheckFeatureSupport\u201d calls in a \u201cFAILED()\u201d macro to determine whether the check succeeds.<\/p>\n Now let\u2019s see how it\u2019s done with the new API:<\/p>\n Immediately you\u2019ll find the whole process a lot easier. There\u2019s no need to set up multiple instances to check different features, nor do you need to reinitialize between cap query calls. Plus, you don\u2019t need to find out which feature groups contain the caps you\u2019d like to query about. With a single instance of CD3DX12FeatureSupport and one single initialization, you can query any cap directly by calling a function of the same name.<\/p>\n What if an old version of D3D12 runtime doesn\u2019t recognize a feature group and the feature check failed? The cap function will return a default \u201cunsupported\u201d value, which is usually 0 or false. It makes sense since the D3D12 runtime cannot support a cap or feature unless it knows about it.<\/p>\n In the second example we deal with FEATURE_LEVELS, which used to have a complicated check routine. With the old API, you need to pass in an array of \u201cD3D_FEATURE_LEVEL\u201d enums, along with the size of that array. The API then picks the highest supported level in the current runtime from the array.<\/p>\n That works but sounds counter-intuitive. We know the feature level enums are listed in increasing order where a newer level has a larger enum. We also know that the feature levels are backwards compatible. So why don\u2019t we just obtain the feature level of the runtime and compare with what we want? The new API allows you to do exactly that:<\/p>\n The above examples illustrated the key characteristics of the new CD3DX12FeatureSupport class:<\/p>\n We\u2019ve demonstrated the general steps for using the new API:<\/p>\n There are some special cases. Some caps are renamed to be more distinguishable in the new API class (for example, \u201cSupported\u201d from \u201cD3D12_FEATURE_DATA_EXISTING_HEAPS\u201d becomes \u201cExistingHeapsSupported()\u201d). Other cap query functions may have different signatures due to their complicated in\/out patterns.<\/p>\n Before the official documentation comes out, we have some resources to help you get started with this new API. Since the CD3DX12FeatureSupport class is part of the open-source DirectX-Headers repo<\/a> available on GitHub, you have access to all its definition and implementation. This can give you a clear idea on how the new API is implemented and what it\u2019s doing behind the scenes. We\u2019ve also provided a program in the same repo (test\/feature_check_test.cpp<\/a>) that contains examples of how to query each cap with the new APIs. It also comes with correctness checks; you can compile and run it to make sure the new API returns the same results as the old API.<\/p>\n We hope this new API provides a better experience for checking feature support in Direct3D!<\/p>\n","protected":false},"excerpt":{"rendered":" Background Direct3D can perform a lot of different operations. We use \u201ccapability\u201d or \u201ccap\u201d to describe what the library can do. Direct3D 12 has a single API, ID3D12Device::CheckFeatureSupport, which tells us whether a cap is supported and its level of support in the runtime environment. Here’s the function signature: HRESULT CheckFeatureSupport( D3D12_FEATURE Feature, void *pFeatureSupportData, […]<\/p>\n","protected":false},"author":67959,"featured_media":12651,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[],"class_list":["post-4950","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-directx"],"acf":[],"blog_post_summary":" Background Direct3D can perform a lot of different operations. We use \u201ccapability\u201d or \u201ccap\u201d to describe what the library can do. Direct3D 12 has a single API, ID3D12Device::CheckFeatureSupport, which tells us whether a cap is supported and its level of support in the runtime environment. Here’s the function signature: HRESULT CheckFeatureSupport( D3D12_FEATURE Feature, void *pFeatureSupportData, […]<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/directx\/wp-json\/wp\/v2\/posts\/4950","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/devblogs.microsoft.com\/directx\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/devblogs.microsoft.com\/directx\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/directx\/wp-json\/wp\/v2\/users\/67959"}],"replies":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/directx\/wp-json\/wp\/v2\/comments?post=4950"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/directx\/wp-json\/wp\/v2\/posts\/4950\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/directx\/wp-json\/wp\/v2\/media\/12651"}],"wp:attachment":[{"href":"https:\/\/devblogs.microsoft.com\/directx\/wp-json\/wp\/v2\/media?parent=4950"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/directx\/wp-json\/wp\/v2\/categories?post=4950"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/directx\/wp-json\/wp\/v2\/tags?post=4950"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}HRESULT CheckFeatureSupport(\r\n D3D12_FEATURE Feature,\r\n void *pFeatureSupportData,\r\n UINT FeatureSupportDataSize\r\n);\r\n\r\n<\/pre>\n
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Solution: The new \u201cCD3DX12FeatureSupport\u201d class<\/h3>\n
Case 1: Multiple queries from different feature groups<\/h4>\n
\/\/ Old API\r\n\r\nD3D12_FEATURE_DATA_D3D12_OPTIONS dOptions;\r\ndevice->CheckFeatureSupport(\r\n D3D12_FEATURE_D3D12_OPTIONS,\r\n &dOptions,\r\n sizeof(D3D12_FEATURE_DATA_D3D12_OPTIONS)\r\n);\r\nBOOL ROVsSupported = dOptions.ROVsSupported;\r\n\r\nD3D12_FEATURE_DATA_D3D12_OPTIONS1 dOptions1;\r\ndevice->CheckFeatureSupport(\r\n D3D12_FEATURE_D3D12_OPTIONS1,\r\n &dOptions1,\r\n sizeof(D3D12_FEATURE_DATA_D3D12_OPTIONS1)\r\n);\r\nBOOL WaveOps = dOptions1.WaveOps;\r\n\r\nD3D12_FEATURE_DATA_D3D12_OPTIONS5 dOptions5;\r\ndevice->CheckFeatureSupport(\r\n D3D12_FEATURE_D3D12_OPTIONS5,\r\n &dOptions5,\r\n sizeof(D3D12_FEATURE_DATA_D3D12_OPTIONS5)\r\n);\r\nD3D12_RAYTRACING_TIER RaytracingTier = dOptions5.RaytracingTier;\r\n\r\n<\/pre>\n
\/\/ New API\r\n\r\nCD3DX12FeatureSupport features;\r\nfeatures.Init(device);\r\nBOOL ROVsSupported = features.ROVsSupported();\r\nBOOL WaveOps = features.WaveOps();\r\nD3D12_RAYTRACING_TIER RaytracingTier = features.RaytracingTier();<\/pre>\n
Case 2: Querying the more complex FEATURE_LEVELS<\/h4>\n
\/\/ Old API\r\n\r\nD3D12_FEATURE_DATA_FEATURE_LEVELS dLevels;\r\nD3D_FEATURE_LEVEL aLevels [] =\r\n{\r\n D3D_FEATURE_LEVEL_12_2,\r\n D3D_FEATURE_LEVEL_12_1,\r\n D3D_FEATURE_LEVEL_12_0,\r\n ...\r\n};\r\ndLevels.NumFeatureLevels = sizeof(aLevels) \/ sizeof(D3D_FEATURE_LEVEL);\r\ndLevels.pFeatureLevelsRequested = aLevels;\r\ndevice->CheckFeatureSupport(\r\n D3D12_FEATURE_FEATURE_LEVELS,\r\n &dLevels,\r\n sizeof(D3D12_FEATURE_DATA_FEATURE_LEVELS)\r\n);\r\nD3D_FEATURE_LEVEL MaxFeatureLevel = dLevels.MaxSupportedFeatureLevel;\r\n\r\n<\/pre>\n\/\/ New API\r\n\r\nCD3DX12FeatureSupport features;\r\nfeatures.Init(device);\r\nD3D_FEATURE_LEVEL MaxFeatureLevel = features.MaxSupportedFeatureLevel();\r\n\r\n<\/pre>\n
Summary:<\/h4>\n
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Usage and Resources<\/h3>\n
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