Merge pull request #68 from orange-cpp/feature/screen_to_world

Feature/screen to world

CMakeLists.txt

@@ -100,6 +100,7 @@ target_compile_features(${PROJECT_NAME} PUBLIC cxx_std_23)
 if (OMATH_BUILD_TESTS)
     add_subdirectory(extlibs)
     add_subdirectory(tests)
+    target_compile_definitions(${PROJECT_NAME} PUBLIC OMATH_BUILD_TESTS)
 endif ()
 
 if (OMATH_BUILD_EXAMPLES)

include/omath/projection/camera.hpp

@@ -4,13 +4,18 @@
 
 #pragma once
 
-#include "omath/projection/error_codes.hpp"
 #include "omath/linear_algebra/mat.hpp"
 #include "omath/linear_algebra/vector3.hpp"
+#include "omath/projection/error_codes.hpp"
 #include <expected>
 #include <omath/angle.hpp>
 #include <type_traits>
 
+#ifdef OMATH_BUILD_TESTS
+// ReSharper disable once CppInconsistentNaming
+class UnitTestProjection_Projection_Test;
+#endif
+
 namespace omath::projection
 {
     class ViewPort final
@@ -45,6 +50,9 @@ namespace omath::projection
     requires CameraEngineConcept<TraitClass, Mat4X4Type, ViewAnglesType>
     class Camera final
     {
+#ifdef OMATH_BUILD_TESTS
+        friend UnitTestProjection_Projection_Test;
+#endif
     public:
         ~Camera() = default;
         Camera(const Vector3<float>& position, const ViewAnglesType& view_angles, const ViewPort& view_port,
@@ -164,6 +172,31 @@ namespace omath::projection
 
             return Vector3<float>{projected.at(0, 0), projected.at(1, 0), projected.at(2, 0)};
         }
+        [[nodiscard]]
+        std::expected<Vector3<float>, Error> view_port_to_screen(const Vector3<float>& ndc) const noexcept
+        {
+            const auto inv_view_proj = get_view_projection_matrix().inverted();
+
+            if (!inv_view_proj)
+                return std::unexpected(Error::INV_VIEW_PROJ_MAT_DET_EQ_ZERO);
+
+            auto inverted_projection =
+                    inv_view_proj.value() * mat_column_from_vector<float, Mat4X4Type::get_store_ordering()>(ndc);
+
+            if (!inverted_projection.at(3, 0))
+                return std::unexpected(Error::WORLD_POSITION_IS_OUT_OF_SCREEN_BOUNDS);
+
+            inverted_projection /= inverted_projection.at(3, 0);
+
+            return Vector3<float>{inverted_projection.at(0, 0), inverted_projection.at(1, 0),
+                                  inverted_projection.at(2, 0)};
+        }
+
+        [[nodiscard]]
+        std::expected<Vector3<float>, Error> screen_to_world(const Vector3<float>& screen_pos) const noexcept
+        {
+            return view_port_to_screen(screen_to_dnc(screen_pos));
+        }
 
     protected:
         ViewPort m_view_port{};
@@ -186,19 +219,25 @@ namespace omath::projection
 
         [[nodiscard]] Vector3<float> ndc_to_screen_position(const Vector3<float>& ndc) const noexcept
         {
-/*
+            /*
-                    ^
+                                ^
-                    |        y
+                                |        y
-                1   |
+                            1   |
-                    |
+                                |
-                    |
+                                |
-        -1 ---------0--------- 1  --> x
+                    -1 ---------0--------- 1  --> x
-                    |
+                                |
-                    |
+                                |
-               -1   |
+                           -1   |
-                    v
+                                v
-*/
+            */
             return {(ndc.x + 1.f) / 2.f * m_view_port.m_width, (1.f - ndc.y) / 2.f * m_view_port.m_height, ndc.z};
         }
+
+        [[nodiscard]] Vector3<float> screen_to_dnc(const Vector3<float>& screen_pos) const noexcept
+        {
+            return {screen_pos.x / m_view_port.m_width * 2.f - 1.f, 1.f - screen_pos.y / m_view_port.m_height * 2.f,
+                    screen_pos.z};
+        }
     };
 } // namespace omath::projection

include/omath/projection/error_codes.hpp

@@ -10,5 +10,6 @@ namespace omath::projection
     enum class Error : uint16_t
     {
         WORLD_POSITION_IS_OUT_OF_SCREEN_BOUNDS,
+        INV_VIEW_PROJ_MAT_DET_EQ_ZERO,
     };
 }

tests/general/unit_test_projection.cpp

@@ -13,8 +13,12 @@ TEST(UnitTestProjection, Projection)
     const auto cam = omath::source_engine::Camera({0, 0, 0}, omath::source_engine::ViewAngles{}, {1920.f, 1080.f}, fov,
                                                   0.01f, 1000.f);
 
-    const auto projected = cam.world_to_screen({1000, 0, 50});
+    const auto projected = cam.world_to_screen({1000.f, 0, 50.f});
+    const auto result = cam.screen_to_world(projected.value());
+    const auto result2 = cam.world_to_screen(result.value());
 
+    EXPECT_EQ(static_cast<omath::Vector2<float>>(projected.value()),
+              static_cast<omath::Vector2<float>>(result2.value()));
     EXPECT_NEAR(projected->x, 960.f, 0.001f);
     EXPECT_NEAR(projected->y, 504.f, 0.001f);
     EXPECT_NEAR(projected->z, 1.f, 0.001f);