Method PrepareWeatherParticles

TombEngine/Renderer/RendererDrawEffect.cpp:1055–1213

	}

	void Renderer::PrepareWeatherParticles(RenderView& view) 
	{
		constexpr auto SNOW_CLUSTER_SPREAD = BLOCK(1.0f);
		constexpr auto RAIN_CLUSTER_SPREAD = BLOCK(1.0f);

		constexpr auto RAIN_WIDTH_NEAR = 1.5f;
		constexpr auto RAIN_WIDTH_FAR = 15.0f;

		for (const auto& part : Weather.GetParticles())
		{
			if (!part.Enabled)
				continue;

			auto pos  = Vector3::Lerp(part.PrevPosition, part.Position, GetInterpolationFactor());
			auto size = Lerp(part.PrevSize, part.Size, GetInterpolationFactor());

			// Underwater dust does not need clustering.
			if (part.Type == WeatherType::None)
			{
				if (!view.Camera.Frustum.SphereInFrustum(pos, size))
					continue;

				if (!CheckIfSlotExists(ID_DEFAULT_SPRITES, "Underwater dust rendering"))
					continue;

				AddSpriteBillboard(
					&_sprites[Objects[ID_DEFAULT_SPRITES].meshIndex + SPR_UNDERWATERDUST],
					pos,
					Color(1.0f, 1.0f, 1.0f, part.Transparency()),
					0.0f, 1.0f, Vector2(size),
					BlendMode::Additive, true, view);

				continue;
			}

			// Clamp cluster size to 1.
			int clusterSize = std::max(1, part.ClusterSize);

			// If particle is dying, immediately cancel the cluster.
			if (part.Stopped)
				clusterSize = 1;

			auto finalPos = pos;
			auto finalScale = size;

			for (int i = 0; i < clusterSize; i++)
			{
				// Combine particle index and cluster index for unique seeding.
				int uniqueSeed = part.UniqueID + i;

				if (i > 0)
				{
					// Use bits from uniqueSeed to determine distribution pattern.
					float spread = part.Type == WeatherType::Snow ? SNOW_CLUSTER_SPREAD : RAIN_CLUSTER_SPREAD;
					float offsetBase = spread * ((i + 1) / (float)clusterSize);

					// Use bits 0, 1, 2 for axis signs.
					// Snow Y axis is always negative, so that snowflakes don't sink into room geometry.