Primitives: tangents in the 3D grid primitive.

mosra · Mar 22, 2020 · b168616 · b168616
1 parent 1b776e1
commit b168616
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Showing 4 changed files with 197 additions and 183 deletions.
diff --git a/doc/changelog.dox b/doc/changelog.dox
@@ -195,8 +195,9 @@ See also:
 @subsubsection changelog-latest-new-primitives Primitives library
 
 -   @ref Primitives::capsule3DSolid(), @ref Primitives::circle3DSolid(),
-    @ref Primitives::coneSolid(), @ref Primitives::cylinderSolid() and
-    @ref Primitives::uvSphereSolid() can now have tangents as well
+    @ref Primitives::coneSolid(), @ref Primitives::cylinderSolid(),
+    @ref Primitives::grid3DSolid() and @ref Primitives::uvSphereSolid() can now
+    have tangents as well
 
 @subsubsection changelog-latest-new-scenegraph SceneGraph library
 

diff --git a/src/Magnum/Primitives/Grid.cpp b/src/Magnum/Primitives/Grid.cpp
@@ -56,16 +56,20 @@ Trade::MeshData grid3DSolid(const Vector2i& subdivisions, const GridFlags flags)
         }
     }
 
-    /* Allocate interleaved array for all vertex data */
+    /* Calculate attribute count and vertex size */
     std::size_t stride = sizeof(Vector3);
     std::size_t attributeCount = 1;
     if(flags & GridFlag::Normals) {
-        ++attributeCount;
         stride += sizeof(Vector3);
+        ++attributeCount;
     }
-    if(flags & GridFlag::TextureCoordinates) {
+    if(flags & GridFlag::Tangents) {
+        stride += sizeof(Vector4);
         ++attributeCount;
+    }
+    if(flags & GridFlag::TextureCoordinates) {
         stride += sizeof(Vector2);
+        ++attributeCount;
     }
     Containers::Array<char> vertexData{stride*vertexCount.product()};
     Containers::Array<Trade::MeshAttributeData> attributes{attributeCount};
@@ -86,8 +90,7 @@ Trade::MeshData grid3DSolid(const Vector2i& subdivisions, const GridFlags flags)
                 positions[i++] = {(Vector2(x, y)/Vector2(faceCount))*2.0f - Vector2{1.0f}, 0.0f};
     }
 
-    /* Fill normals, if any. It's always the second attribute, right after
-       positions. */
+    /* Fill normals and tangents, if any. Those are the same for all. */
     if(flags & GridFlag::Normals) {
         Containers::StridedArrayView1D<Vector3> normals{vertexData,
             reinterpret_cast<Vector3*>(vertexData.begin() + attributeOffset),
@@ -97,6 +100,15 @@ Trade::MeshData grid3DSolid(const Vector2i& subdivisions, const GridFlags flags)
         attributeOffset += sizeof(Vector3);
         for(auto&& i: normals) i = Vector3::zAxis(1.0f);
     }
+    if(flags & GridFlag::Tangents) {
+        Containers::StridedArrayView1D<Vector4> tangents{vertexData,
+            reinterpret_cast<Vector4*>(vertexData.begin() + attributeOffset),
+            std::size_t(vertexCount.product()), std::ptrdiff_t(stride)};
+        attributes[attributeIndex++] =
+            Trade::MeshAttributeData{Trade::MeshAttribute::Tangent, tangents};
+        attributeOffset += sizeof(Vector4);
+        for(auto&& i: tangents) i = {1.0f, 0.0f, 0.0f, 1.0f};
+    }
 
     if(flags & GridFlag::TextureCoordinates) {
         Containers::StridedArrayView1D<Vector2> textureCoords{vertexData,
@@ -109,8 +121,6 @@ Trade::MeshData grid3DSolid(const Vector2i& subdivisions, const GridFlags flags)
             textureCoords[i] = positions[i].xy()*0.5f + Vector2{0.5f};
     }
 
-    /* Not using a compile-time attribute array because there's way too many
-       combinations */
     return Trade::MeshData{MeshPrimitive::Triangles,
         std::move(indexData), Trade::MeshIndexData{indices},
         std::move(vertexData), std::move(attributes)};

diff --git a/src/Magnum/Primitives/Grid.h b/src/Magnum/Primitives/Grid.h
@@ -70,8 +70,16 @@ enum class GridFlag: UnsignedByte {
      * Generate normals in positive Z direction.
      * @m_deprecated_since_latest Use @ref GridFlag::Normals instead.
      */
-    GenerateNormals CORRADE_DEPRECATED_ENUM("use Normals instead") = Normals
+    GenerateNormals CORRADE_DEPRECATED_ENUM("use Normals instead") = Normals,
     #endif
+
+    /**
+     * Generate four-component tangents. The last component can be used to
+     * reconstruct a bitangent as described in the documentation of
+     * @ref Trade::MeshAttribute::Tangent.
+     * @m_since_latest
+     */
+    Tangents = 1 << 2
 };
 
 /**
@@ -89,8 +97,8 @@ CORRADE_ENUMSET_OPERATORS(GridFlags)
 2x2 grid in the XY plane with normals in positive Z direction.
 @ref MeshPrimitive::Triangles with @ref MeshIndexType::UnsignedInt indices,
 interleaved @ref VertexFormat::Vector3 positions, optional
-@ref VertexFormat::Vector3 normals and @ref VertexFormat::Vector2 texture
-coordinates.
+@ref VertexFormat::Vector3 normals, optional @ref VertexFormat::Vector4
+tangents and optional @ref VertexFormat::Vector2 texture coordinates.
 
 @image html primitives-grid3dsolid.png width=256px