Resampled Importance Sampling bxdfs by devshgraphicsprogramming · Pull Request #1027 · Devsh-Graphics-Programming/Nabla

devshgraphicsprogramming · 2026-03-20T11:08:54Z

Description

Testing

TODO list:

…ession reciprocation (swapping of interface order) Unfortunately I realized our THINDIELECTRIC correction is badly designed

…a, won't implement right now

… mitsuba_xml_2_material_frontend

…ff last

@Themperror

Point Boost to the exact Wave one-line backport for emitted pragma newlines, remove the temporary local pragma workaround, and keep the remaining include-path fixes in Nabla. This leaves the Wave pragma issue fixed at the dependency level while preserving the Nabla-side fixes for Windows backslash includes and single-leading-slash virtual includes. Thanks to @Themperror for the additional pragma and include repros. Those made it straightforward to verify the dependency-level fix and drop the local workaround cleanly.

…dates Fix remaining preprocess bugs and backport Wave pragma fix

…te-nsc-windows-x64-release-master CI: Promote NSC channel to 66da590

…mmon bxdfs

include/nbl/builtin/hlsl/bxdf/base/lambertian.hlsl

include/nbl/builtin/hlsl/bxdf/common.hlsl

devshgraphicsprogramming · 2026-03-20T11:21:06Z

include/nbl/builtin/hlsl/bxdf/common.hlsl

+    ((NBL_CONCEPT_REQ_EXPR_RET_TYPE)((bxdf.eval_and_weight(_sample, aniso, anisocache)), ::nbl::hlsl::is_same_v, typename T::quotient_pdf_type))
    ((NBL_CONCEPT_REQ_EXPR_RET_TYPE)((bxdf.pdf(_sample, aniso, anisocache)), ::nbl::hlsl::is_same_v, typename T::scalar_type))
-    ((NBL_CONCEPT_REQ_EXPR_RET_TYPE)((bxdf.quotient_and_pdf(_sample, aniso, anisocache)), ::nbl::hlsl::is_same_v, typename T::quotient_pdf_type))
+    ((NBL_CONCEPT_REQ_EXPR_RET_TYPE)((bxdf.quotient_and_weight(_sample, aniso, anisocache)), ::nbl::hlsl::is_same_v, typename T::quotient_pdf_type))


lets make all BxDFs have a cache type which goes from generate to quotient_and_weight but then microfacet_bxdf_common would be the weird one that puts a further constraint that the anisocache_type needs to fit some concept for Cook Torrance to be useful

and allow a 2nd cache type just for eval_and_weight (the two can obviously be identical in practice, e.g. our base impl for now)

you could actually get rid of microfacex_bdf_common and the iso_microfacet concept (basically the entire block in namespace impl ehere)

and just check that {Isotropic}MicrofacetB{R|S}DF = {Isotropic}B{R|S}DF<T> && (Isotropic ? CreatableIsotropicMicrofacetCache<typedef T::cache_type>:AnisotropicMicrofacetCache<typedef T::cache_type>);

devshgraphicsprogramming · 2026-03-20T11:28:15Z

tools/nsc/main.cpp

+    if (!system || outputPath.empty())
+        return false;
+
+    const auto parent = outputPath.parent_path();
+    if (!parent.empty() && !system->isDirectory(parent))
+    {
+        if (!system->createDirectory(parent))
+            return false;
+    }
+
+    auto tempPath = outputPath;
+    tempPath += ".tmp";
+    system->deleteFile(tempPath);
+
+    smart_refctd_ptr<IFile> outputFile;
+    {
+        ISystem::future_t<smart_refctd_ptr<IFile>> future;
+        system->createFile(future, tempPath, IFileBase::ECF_WRITE);
+        if (!future.wait())
+            return false;
+
+        auto lock = future.acquire();
+        if (!lock)
+            return false;
+        lock.move_into(outputFile);
+    }
+    if (!outputFile)
+        return false;
+
+    if (!content.empty())
+    {
+        IFile::success_t success;
+        outputFile->write(success, content.data(), 0ull, content.size());
+        if (!success)
+        {
+            outputFile = nullptr;
+            system->deleteFile(tempPath);
+            return false;
+        }
+    }
+    outputFile = nullptr;
+
+    system->deleteFile(outputPath);
+    const auto moveError = system->moveFileOrDirectory(tempPath, outputPath);
+    if (moveError)
+    {
+        system->deleteFile(tempPath);
+        return false;
+    }
+
+    return true;


@AnastaZIuk do you think you could add an option to createFile flags (or pack the path+ IFileBase flaggs into a strcut) to create all the directories needed on the way to the path ?

cold be useful

…_2_material_frontend

include/nbl/builtin/hlsl/bxdf/base/cook_torrance_base.hlsl

include/nbl/builtin/hlsl/bxdf/common.hlsl

…cet checks cache with concept

devshgraphicsprogramming · 2026-03-24T15:20:22Z

include/nbl/builtin/hlsl/bxdf/base/lambertian.hlsl

+    struct Cache {};
+    using isocache_type = Cache;
+    using anisocache_type = Cache;
+    using evalcache_type = Cache;


there should be no evalcache_type, its still same cache as for quotient and generate

But having an evalAndWeight with an overload that takes it should be a Cook Torrance / Microfacet thing only

devshgraphicsprogramming · 2026-03-24T15:21:40Z

include/nbl/builtin/hlsl/bxdf/common.hlsl

    ((NBL_CONCEPT_REQ_TYPE)(T::anisotropic_interaction_type))
    ((NBL_CONCEPT_REQ_TYPE)(T::sample_type))
+    ((NBL_CONCEPT_REQ_TYPE)(T::anisocache_type))
+    ((NBL_CONCEPT_REQ_TYPE)(T::evalcache_type))


don't require a separate evaluation cache type

devshgraphicsprogramming · 2026-03-24T15:22:45Z

include/nbl/builtin/hlsl/bxdf/common.hlsl

    ((NBL_CONCEPT_REQ_TYPE)(T::isotropic_interaction_type))
    ((NBL_CONCEPT_REQ_TYPE)(T::isocache_type))
-    ((NBL_CONCEPT_REQ_EXPR_RET_TYPE)((bxdf.eval_and_weight(_sample, iso, isocache)), ::nbl::hlsl::is_same_v, typename T::quotient_pdf_type))
+    ((NBL_CONCEPT_REQ_EXPR_RET_TYPE)((bxdf.evalAndWeight(_sample, iso, evalcache)), ::nbl::hlsl::is_same_v, typename T::quotient_pdf_type))


evalAndWeight taking the anisocache or isocache should be an extra overload in the imcrofacet BxDF concepts

…l methods

include/nbl/builtin/hlsl/bxdf/base/cook_torrance_base.hlsl

devshgraphicsprogramming · 2026-03-25T12:55:46Z

include/nbl/builtin/hlsl/bxdf/base/cook_torrance_base.hlsl

-        }
+        using g2g1_query_type = typename N::g2g1_query_type;
+        g2g1_query_type gq = ndf.template createG2G1Query<sample_type, Interaction>(_sample, interaction);
+        scalar_type G2_over_G1 = ndf.template G2_over_G1<sample_type, Interaction, MicrofacetCache>(gq, _sample, interaction, cache);


check how well this behaves as roughness ->0 we don't want to have NaNs

We have a check in ndfs for a<float_min

we're bypassing a bunch of things , so there's no check

Nabla/include/nbl/builtin/hlsl/bxdf/ndf/ggx.hlsl

Line 364 in 2539522

scalar_type G2_over_G1(NBL_CONST_REF_ARG(g2g1_query_type) query, NBL_CONST_REF_ARG(LS) _sample, NBL_CONST_REF_ARG(Interaction) interaction, NBL_CONST_REF_ARG(MicrofacetCache) cache) NBL_CONST_MEMBER_FUNC

you will in-fact assert in the constructor

Nabla/include/nbl/builtin/hlsl/bxdf/ndf/ggx.hlsl

Line 236 in 2539522

enable_if_t<C::value && !IsAnisotropic, g2g1_query_type> createG2G1Query(NBL_CONST_REF_ARG(LS) _sample, NBL_CONST_REF_ARG(Interaction) interaction) NBL_CONST_MEMBER_FUNC

of the query

Nabla/include/nbl/builtin/hlsl/bxdf/ndf/ggx.hlsl

Line 104 in 2539522

assert(a2 >= numeric_limits<scalar_type>::min);

I mean the HLSL compiles to C++ and we have a unit test so you can go through it with a debugger I guess 🙃

I think if you know/check the PDF not being INF before setting G2_over_G1 you can guard against that

include/nbl/builtin/hlsl/bxdf/base/cook_torrance_base.hlsl

…xisting cache type too

devshgraphicsprogramming · 2026-03-26T09:41:59Z

include/nbl/builtin/hlsl/bxdf/common.hlsl

+#define NBL_CONCEPT_PARAM_3 (evalcache, typename T::evalcache_type)
+NBL_CONCEPT_BEGIN(4)
+#define bxdf NBL_CONCEPT_PARAM_T NBL_CONCEPT_PARAM_0
+#define _sample NBL_CONCEPT_PARAM_T NBL_CONCEPT_PARAM_1
+#define aniso NBL_CONCEPT_PARAM_T NBL_CONCEPT_PARAM_2
+#define evalcache NBL_CONCEPT_PARAM_T NBL_CONCEPT_PARAM_3
+NBL_CONCEPT_END(
+    ((NBL_CONCEPT_REQ_TYPE)(T::evalcache_type))
+    ((NBL_CONCEPT_REQ_TYPE_ALIAS_CONCEPT)(bxdf_common, T))
+    ((NBL_CONCEPT_REQ_TYPE_ALIAS_CONCEPT)(AnisotropicMicrofacetCache, typename T::anisocache_type))
+    ((NBL_CONCEPT_REQ_EXPR_RET_TYPE)((bxdf.evalAndWeight(_sample, aniso, evalcache)), ::nbl::hlsl::is_same_v, typename T::value_weight_type))


cool but evalcache needs to be just microfacetCache and be of type T::cache_type

no evalcache_type

devshgraphicsprogramming · 2026-03-26T09:43:22Z

include/nbl/builtin/hlsl/path_tracing/concepts.hlsl

    ((NBL_CONCEPT_REQ_TYPE)(T::object_handle_type))
    ((NBL_CONCEPT_REQ_EXPR_RET_TYPE)((sqr.getSample()), ::nbl::hlsl::is_same_v, typename T::sample_type))
-    ((NBL_CONCEPT_REQ_EXPR_RET_TYPE)((sqr.getQuotientPdf()), ::nbl::hlsl::is_same_v, typename T::quotient_pdf_type))
+    ((NBL_CONCEPT_REQ_EXPR_RET_TYPE)((sqr.getQuotientPdf()), ::nbl::hlsl::is_same_v, typename T::quotient_weight_type))


getQuotientPdf rename to getQuotientAndWeight

kevyuu and others added 24 commits March 14, 2026 10:44

Fix checking valid jpeg file logic

5def0b4

get opacity going!

f93f430

really struggling with TWO_SIDED

1a7bf02

add CFrontendIR node copying, stack reversal and individual BxDF expr…

0dc31aa

…ession reciprocation (swapping of interface order) Unfortunately I realized our THINDIELECTRIC correction is badly designed

Beer node needs a thickness unfortunately.

8aff0f7

quick hack around normalmaps and bumpmaps, sketch out the general ide…

1b0b6f3

…a, won't implement right now

Merge remote-tracking branch 'remotes/origin/hotfix_jpeg_loader' into…

6a4e8df

… mitsuba_xml_2_material_frontend

move UV transform to front of SParameterSet, keep variable length stu…

0c1e045

…ff last

implement BLEND_BSDF

850536c

I forgot that for blends all layers need to be blended!

011e7f0

I don't want to admit how long it took me to debug this one

2b34047

fix the last thing in the material frontend

2d3719f

fix TLAS export when Polygon Geometry can't be made into a BLAS

ad0cf8d

merge master

5d2568b

Fix Wave include paths and failure dumps

c86f8e1

Clean up preprocess failure plumbing

4871e24

Merge pull request #1025 from Devsh-Graphics-Programming/preprocessUp…

e4df2b2

…dates Fix remaining preprocess bugs and backport Wave pragma fix

Use upstream gh-pages action for badges

66da590

Promote NSC channel 66da590

f830a47

Merge pull request #1026 from Devsh-Graphics-Programming/ci/nsc-promo…

00017ad

…te-nsc-windows-x64-release-master CI: Promote NSC channel to 66da590

Merge branch 'master' into ris_bxdfs

83e30e4

change concepts for bxdf to *_and_weight methods, make changes for co…

067d107

…mmon bxdfs

pdf method renamed to denominator, don't expect to be used

fc6deb8

devshgraphicsprogramming changed the title ~~Ris bxdfs~~ Resampled Importance Sampling bxdfs Mar 20, 2026

devshgraphicsprogramming commented Mar 20, 2026

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devshgraphicsprogramming commented Mar 20, 2026

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Merge remote-tracking branch 'remotes/origin/master' into mitsuba_xml…

c292f41

…_2_material_frontend

devshgraphicsprogramming commented Mar 23, 2026

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devshgraphicsprogramming mentioned this pull request Mar 23, 2026

Address path tracer merge leftover comments #991

Merged

keptsecret added 5 commits March 24, 2026 10:03

merge master, fix conflicts

95a3862

pass ray to nee generate instead, store depth in ray

946c9c7

nee deferredPdf is deferredWeight

4f4421d

all bxdfs have a cache type from generate to quotient_weight, microfa…

a70f420

…cet checks cache with concept

eval should have its own cache type in concepts

dab4a18

devshgraphicsprogramming commented Mar 24, 2026

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keptsecret added 5 commits March 25, 2026 10:49

minor typo bug fixes

fb878a6

eval returns a value_and_weight type, fixed some bugs in bxdf concept

4171059

made value_and_pdf compose from value_and_weight

0e16279

reuse quant query and other stuff from forwardPdf in quotient and eva…

345865f

…l methods

reuse reflectance from forwardpdf in eval

a98cd45

devshgraphicsprogramming commented Mar 25, 2026

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devshgraphicsprogramming commented Mar 25, 2026

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devshgraphicsprogramming commented Mar 25, 2026

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devshgraphicsprogramming mentioned this pull request Mar 25, 2026

Env map importance sampling #969

Open

keptsecret added 4 commits March 26, 2026 10:41

renamed quotient_pdf type to quotient_weight type

d0ed7d3

minor fixes to cook torrance, removed redundant functions

110547a

only microfacet bxdfs need eval cache type, allow for overload with e…

ef9156e

…xisting cache type too

latest example

05124c2

devshgraphicsprogramming commented Mar 26, 2026

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devshgraphicsprogramming commented Mar 20, 2026

Description

Testing

TODO list:

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