Add normalmap test

src/bsdfs/tests/test_normalmap.py

@@ -0,0 +1,107 @@
+import pytest
+import drjit as dr
+import mitsuba as mi
+import numpy as np
+
+def test01_empty(variants_vec_backends_once_rgb):
+    raw_bsdf : mi.BSDF = mi.load_dict({
+        'type': 'roughconductor',
+        'distribution': 'ggx',
+        'alpha_u': 0.2,
+        'alpha_v': 0.05,
+        'material': 'Al'
+    })
+    normalmap_bsdf : mi.BSDF = mi.load_dict(
+    {
+        'type': 'normalmap',
+        'normalmap': {
+            'type': 'srgb',
+            'color': [ 0.5, 0.5, 1.0 ]
+        },
+        'nested_bsdf': raw_bsdf
+    })
+
+    rng : mi.Sampler = mi.load_dict({
+        'type': 'ldsampler'
+    })
+    rng.seed(0, 1024)
+    sample1 = rng.next_1d()
+    sample2 = rng.next_2d()
+
+    si = mi.SurfaceInteraction3f()
+    si.sh_frame = mi.Frame3f(mi.Vector3f(1, 1, 1))
+    si.wi = mi.Vector3f(0, 0, 1)
+
+    bs_ref, weight_ref = raw_bsdf.sample(mi.BSDFContext(), si, sample1, sample2)
+    bs_test, weight_test = normalmap_bsdf.sample(mi.BSDFContext(), si, sample1, sample2)
+
+    # ignore quantities for zero-weight samples!
+    bs_ref.wo[dr.all(dr.eq(weight_ref, 0))] = 0
+    bs_test.wo[dr.all(dr.eq(weight_test, 0))] = 0
+    bs_ref.pdf[dr.all(dr.eq(weight_ref, 0))] = 0
+    bs_test.pdf[dr.all(dr.eq(weight_test, 0))] = 0
+
+    assert dr.allclose(bs_ref.wo, bs_test.wo)
+    assert dr.allclose(bs_ref.pdf, bs_test.pdf)
+    assert dr.allclose(weight_ref, weight_test)
+
+def test02_tilted(variants_vec_backends_once_rgb):
+    # Construct a "local" frame representing a normal perturbation
+    sin_theta = 0.5
+    cos_theta = 0.5*dr.sqrt(3)
+    s = mi.ScalarVector3f(cos_theta, 0, -sin_theta)
+    t = mi.ScalarVector3f(0, 1, 0)
+    n = mi.ScalarVector3f(sin_theta, 0, cos_theta)
+    normal_frame = mi.Frame3f(s, t, n)
+    raw_bsdf : mi.BSDF = mi.load_dict({
+        'type': 'roughconductor',
+        'distribution': 'ggx',
+        'alpha_u': 0.2,
+        'alpha_v': 0.05,
+        'material': 'Al'
+    })
+    perturbed_bsdf : mi.BSDF = mi.load_dict(
+    {
+        'type': 'normalmap',
+        'normalmap': {
+            'type': 'srgb',
+            'color': n * 0.5 + 0.5
+        },
+        'nested_bsdf': raw_bsdf
+    })
+
+    rng : mi.Sampler = mi.load_dict({
+        'type': 'ldsampler'
+    })
+    rng.seed(0, 1024)
+    sample1 = rng.next_1d()
+    sample2 = rng.next_2d()
+
+    si_original = mi.SurfaceInteraction3f()
+    si_original.sh_frame = mi.Frame3f(mi.Vector3f(1, 1, 1))
+    si_original.wi = mi.Vector3f(0, 0, 1)
+
+    si_perturbed = mi.SurfaceInteraction3f()
+    si_perturbed.sh_frame = mi.Frame3f(si_original.to_world(normal_frame.s), si_original.to_world(normal_frame.t), si_original.to_world(normal_frame.n))
+    si_perturbed.wi = normal_frame.to_local(si_original.wi)
+
+    bs_raw, weight_raw = raw_bsdf.sample(mi.BSDFContext(), si_perturbed, sample1, sample2)
+    bs_test, weight_test = perturbed_bsdf.sample(mi.BSDFContext(), si_original, sample1, sample2)
+
+    # move raw wo to into the perturbed normal frame
+    wo_raw = normal_frame.to_world(bs_raw.wo)
+    wo_test = bs_test.wo
+
+    # mask invalid "raw" samples with inconsistent surface orientations
+    bs_raw.pdf[wo_raw.z * bs_raw.wo.z <= 0] = 0
+    weight_raw[wo_raw.z * bs_raw.wo.z <= 0] = 0
+
+    # ignore quantities for zero-weight samples!
+    wo_raw[dr.all(dr.eq(weight_raw, 0))] = 0
+    wo_test[dr.all(dr.eq(weight_test, 0))] = 0
+    bs_raw.pdf[dr.all(dr.eq(weight_raw, 0))] = 0
+    bs_test.pdf[dr.all(dr.eq(weight_test, 0))] = 0
+
+    assert dr.allclose(wo_raw, wo_test, atol=1e-4)
+    assert dr.allclose(bs_raw.pdf, bs_test.pdf, atol=1e-4)
+    assert dr.allclose(weight_raw, weight_test, atol=2e-4)