Boom exam done!

project/src/HitTest.cpp

@@ -0,0 +1,72 @@
+#include "HitTest.h"
+
+
+
+float CrossZ(const Vector3& p0, const Vector3& p1, const Vector3& point)
+{
+    return (p1.x - p0.x) * (point.y - p0.y)
+           - (p1.y - p0.y) * (point.x - p0.x);
+}
+
+std::optional<Sample> TriangleHitTest(const Vector3& fragPos, const VertexOut& v0, const VertexOut& v1, const VertexOut& v2)
+{
+    Vector3 weights;
+
+    weights.x = CrossZ(v2.position, v1.position, fragPos);
+    if ( weights.x > 0 )
+        return std::nullopt;
+
+    weights.y = CrossZ(v0.position, v2.position, fragPos);
+    if ( weights.y > 0 )
+        return std::nullopt;
+
+    weights.z = CrossZ(v1.position, v0.position, fragPos);
+    if ( weights.z > 0 )
+        return std::nullopt;
+
+    const float totalWeight{ weights.x + weights.y + weights.z };
+
+    const float invTotalWeight{ 1.0f / totalWeight };
+    const Vector3 normWeights{
+            weights.x * invTotalWeight,
+            weights.y * invTotalWeight,
+            weights.z * invTotalWeight
+    };
+
+    const float depth =
+            1 / (normWeights.x / v0.position.w +
+                 normWeights.y / v1.position.w +
+                 normWeights.z / v2.position.w);
+
+    const Vector2 uv =
+            v0.uv * depth * normWeights.x / v0.position.w +
+            v1.uv * depth * normWeights.y / v1.position.w +
+            v2.uv * depth * normWeights.z / v2.position.w;
+
+    const float interpolatedDepth = 1 / (normWeights.x / v0.position.w + normWeights.y / v1.position.w + normWeights.z / v2.position.w);
+
+    auto interpolate  =
+            [&]<typename Type>(const Type& val0, const Type& val1, const Type& val2) -> Type
+            {
+                return (val0 / v0.position.w * normWeights.x +
+                        val1 / v1.position.w * normWeights.y +
+                        val2 / v2.position.w * normWeights.z) * interpolatedDepth;
+
+            };
+
+    //Invert the normal
+    const Vector3 normal = interpolate(v0.normal, v1.normal, v2.normal).Normalized();
+    const Vector3 tangent = interpolate(v0.tangent, v1.tangent, v2.tangent).Normalized();
+    const Vector3 viewDir = interpolate(v0.viewDir, v1.viewDir, v2.viewDir).Normalized();
+
+    return Sample{
+            .uv = uv,
+            .normal = normal,
+            .tangent = tangent,
+            .viewDirection = viewDir,
+            .depth = depth,
+            .weight = normWeights,
+            .mesh = v0.mesh
+    };
+}
+