LibGL+LibSoftGPU+LibGfx: Reimplement normal transformation

We now support generating top-left submatrices from a `Gfx::Matrix`
and we move the normal transformation calculation into
`SoftGPU::Device`. No functional changes.

4 files changed, 22 insertions, 14 deletions

diff --git a/Userland/Libraries/LibGL/GLContext.cpp b/Userland/Libraries/LibGL/GLContext.cpp
index 009c765436..0c0246f25d 100644
--- a/Userland/Libraries/LibGL/GLContext.cpp
+++ b/Userland/Libraries/LibGL/GLContext.cpp
@@ -379,16 +379,7 @@ void GLContext::gl_end()
         VERIFY_NOT_REACHED();
     }
 
-    // Set up normals transform by taking the upper left 3x3 elements from the model view matrix
-    // See section 2.11.3 of the OpenGL 1.5 spec
-    auto const& mv_elements = m_model_view_matrix.elements();
-    auto const model_view_transposed = FloatMatrix3x3(
-        mv_elements[0][0], mv_elements[1][0], mv_elements[2][0],
-        mv_elements[0][1], mv_elements[1][1], mv_elements[2][1],
-        mv_elements[0][2], mv_elements[1][2], mv_elements[2][2]);
-    auto const& normal_transform = model_view_transposed.inverse();
-
-    m_rasterizer.draw_primitives(primitive_type, m_model_view_matrix, normal_transform, m_projection_matrix, m_texture_matrix, m_vertex_list, enabled_texture_units);
+    m_rasterizer.draw_primitives(primitive_type, m_model_view_matrix, m_projection_matrix, m_texture_matrix, m_vertex_list, enabled_texture_units);
 
     m_vertex_list.clear_with_capacity();
 }
diff --git a/Userland/Libraries/LibGfx/Matrix.h b/Userland/Libraries/LibGfx/Matrix.h
index 2e251de293..78be55f48f 100644
--- a/Userland/Libraries/LibGfx/Matrix.h
+++ b/Userland/Libraries/LibGfx/Matrix.h
@@ -13,6 +13,9 @@ namespace Gfx {
 
 template<size_t N, typename T>
 class Matrix {
+    template<size_t U, typename V>
+    friend class Matrix;
+
 public:
     static constexpr size_t Size = N;
 
@@ -173,6 +176,17 @@ public:
         return result;
     }
 
+    template<size_t U>
+    [[nodiscard]] constexpr Matrix<U, T> submatrix_from_topleft() const requires(U > 0 && U < N)
+    {
+        Matrix<U, T> result;
+        for (size_t i = 0; i < U; ++i) {
+            for (size_t j = 0; j < U; ++j)
+                result.m_elements[i][j] = m_elements[i][j];
+        }
+        return result;
+    }
+
 private:
     T m_elements[N][N];
 };
diff --git a/Userland/Libraries/LibSoftGPU/Device.cpp b/Userland/Libraries/LibSoftGPU/Device.cpp
index f5380bb78d..3db74a188a 100644
--- a/Userland/Libraries/LibSoftGPU/Device.cpp
+++ b/Userland/Libraries/LibSoftGPU/Device.cpp
@@ -639,9 +639,8 @@ static void generate_texture_coordinates(Vertex& vertex, RasterizerOptions const
     }
 }
 
-void Device::draw_primitives(PrimitiveType primitive_type, FloatMatrix4x4 const& model_view_transform, FloatMatrix3x3 const& normal_transform,
-    FloatMatrix4x4 const& projection_transform, FloatMatrix4x4 const& texture_transform, Vector<Vertex> const& vertices,
-    Vector<size_t> const& enabled_texture_units)
+void Device::draw_primitives(PrimitiveType primitive_type, FloatMatrix4x4 const& model_view_transform, FloatMatrix4x4 const& projection_transform,
+    FloatMatrix4x4 const& texture_transform, Vector<Vertex> const& vertices, Vector<size_t> const& enabled_texture_units)
 {
     // At this point, the user has effectively specified that they are done with defining the geometry
     // of what they want to draw. We now need to do a few things (https://www.khronos.org/opengl/wiki/Rendering_Pipeline_Overview):
@@ -716,6 +715,10 @@ void Device::draw_primitives(PrimitiveType primitive_type, FloatMatrix4x4 const&
         }
     }
 
+    // Set up normals transform by taking the upper left 3x3 elements from the model view matrix
+    // See section 2.11.3 of the OpenGL 1.5 spec
+    auto normal_transform = model_view_transform.submatrix_from_topleft<3>().transpose().inverse();
+
     // Now let's transform each triangle and send that to the GPU
     auto const viewport = m_options.viewport;
     auto const viewport_half_width = viewport.width() / 2.0f;
diff --git a/Userland/Libraries/LibSoftGPU/Device.h b/Userland/Libraries/LibSoftGPU/Device.h
index af5e1cb0c5..aefc01aa96 100644
--- a/Userland/Libraries/LibSoftGPU/Device.h
+++ b/Userland/Libraries/LibSoftGPU/Device.h
@@ -115,7 +115,7 @@ public:
 
     DeviceInfo info() const;
 
-    void draw_primitives(PrimitiveType, FloatMatrix4x4 const& model_view_transform, FloatMatrix3x3 const& normal_transform, FloatMatrix4x4 const& projection_transform, FloatMatrix4x4 const& texture_transform, Vector<Vertex> const& vertices, Vector<size_t> const& enabled_texture_units);
+    void draw_primitives(PrimitiveType, FloatMatrix4x4 const& model_view_transform, FloatMatrix4x4 const& projection_transform, FloatMatrix4x4 const& texture_transform, Vector<Vertex> const& vertices, Vector<size_t> const& enabled_texture_units);
     void resize(Gfx::IntSize const& min_size);
     void clear_color(FloatVector4 const&);
     void clear_depth(DepthType);