One Triangle Case

UUnderWaterMeshGenerator.Cpp

void UUnderWaterMeshGenerator::AddTrianglesOneAboveWater(TArray<FVertexData> vertexData)
{
	//H is always at position 0
	FVector H = vertexData[0].globalVertexPos;

	//Left of H is M
	//Right of H is L

	//Find the index of M
	int M_index = vertexData[0].index - 1;
	if (M_index < 0)
	{
		M_index = 2;
	}

	//We also need the heights to water
	float h_H = vertexData[0].distance;
	float h_M = 0.0f;
	float h_L = 0.0f;

	FVector M = FVector::ZeroVector;
	FVector L = FVector::ZeroVector;
	//This means M is at position 1 in the List
	if (vertexData[1].index == M_index)
	{
		M = vertexData[1].globalVertexPos;
		L = vertexData[2].globalVertexPos;

		h_M = vertexData[1].distance;
		h_L = vertexData[2].distance;
	}
	else
	{
		M = vertexData[2].globalVertexPos;
		L = vertexData[1].globalVertexPos;

		h_M = vertexData[2].distance;
		h_L = vertexData[1].distance;
	}


	//Now we can calculate where we should cut the triangle to form 2 new triangles
	//because the resulting area will always form a square

	//Point I_M
	FVector MH = H - M;

	float t_M = -h_M / (h_H - h_M);

	FVector MI_M = t_M * MH;

	FVector I_M = MI_M + M;


	//Point I_L
	FVector LH = H - L;

	float t_L = -h_L / (h_H - h_L);

	FVector LI_L = t_L * LH;

	FVector I_L = LI_L + L;


	//Save the data, such as normal, area, etc      
	//2 triangles below the water

	//Save the triangle in reverse order (unreal counter clockwise for some dumb reason)
	UnderWaterTriangleData.Add(FTriangleData(I_L, I_M, M));
	UnderWaterTriangleData.Add(FTriangleData(L, I_L, M));
}