0031302: Visualization, TKOpenGl - wrong tangent space calculation for normal maps

The normal after tangent space calculation has been reverted in order to be in right orientation.
The tangent space calculation has been modified in order to handle back faces with inverted normal.

diff --git a/src/OpenGl/OpenGl_ShaderManager.cxx b/src/OpenGl/OpenGl_ShaderManager.cxx
index ababd4359d9b55875520e484018e345b6e1a1d3a..e5c143a53b418b7e9c702007175763d2de09bf20 100644 (file)
--- a/src/OpenGl/OpenGl_ShaderManager.cxx
+++ b/src/OpenGl/OpenGl_ShaderManager.cxx
@@ -2731,9 +2731,10 @@ Standard_Boolean OpenGl_ShaderManager::prepareStdProgramPhong (Handle(OpenGl_Sha
         EOL"    aDeltaUVMatrix = mat2 (aDeltaUVMatrix[1][1], -aDeltaUVMatrix[0][1], -aDeltaUVMatrix[1][0], aDeltaUVMatrix[0][0]);"
         EOL"    mat2x3 aDeltaVectorMatrix = mat2x3 (dFdx (PositionWorld.xyz), dFdy (PositionWorld.xyz));"
         EOL"    aDeltaVectorMatrix = aDeltaVectorMatrix * aDeltaUVMatrix;"
-        EOL"    aDeltaVectorMatrix[0] = aDeltaVectorMatrix[0] - dot(Normal, aDeltaVectorMatrix[0]) * Normal;"
-        EOL"    aDeltaVectorMatrix[1] = aDeltaVectorMatrix[1] - dot(Normal, aDeltaVectorMatrix[1]) * Normal;"
-        EOL"    Normal = mat3 (-normalize(aDeltaVectorMatrix[0]), -normalize(aDeltaVectorMatrix[1]), Normal) * aMapNormalValue.xyz;"
+        EOL"    aDeltaVectorMatrix[0] = normalize(aDeltaVectorMatrix[0] - dot(Normal, aDeltaVectorMatrix[0]) * Normal);"
+        EOL"    aDeltaVectorMatrix[1] = normalize(aDeltaVectorMatrix[1] - dot(Normal, aDeltaVectorMatrix[1]) * Normal);"
+        EOL"    float aDirection = gl_FrontFacing ? 1.0 : -1.0;"
+        EOL"    Normal = mat3 (aDirection * aDeltaVectorMatrix[0], aDirection * aDeltaVectorMatrix[1], Normal) * aMapNormalValue.xyz;"
         EOL"  }"
         EOL"#endif";
     }

diff --git a/tests/v3d/glsl/pbr_tangent_normal b/tests/v3d/glsl/pbr_tangent_normal
new file mode 100644 (file)
index 0000000..ade81c7
--- /dev/null
+++ b/tests/v3d/glsl/pbr_tangent_normal
@@ -0,0 +1,28 @@
+puts "========"
+puts "0031302: Visualization, TKOpenGl - wrong tangent space calculation for normal maps"
+puts "Test for tangent space orientation."
+puts "========"
+
+pload XDE OCAF MODELING VISUALIZATION
+
+vclear
+vclose ALL
+
+vinit v -w 1024 -h 1024
+vcamera -persp
+vbackground -cubemap [locate_data_file Circus_CubeMap_V.png]
+vrenderparams -shadingModel PBR
+
+vlight -clear
+vlight -add ambient
+
+catch { Close D }
+ReadGltf D [locate_data_file bug31302_NormalTangentTest.gltf]
+XDisplay -dispmode 1 D
+
+vfront
+vfit
+vdump $imagedir/${casename}_front.png
+
+vback
+vdump $imagedir/${casename}_back.png