Fog effect when camera is inside cloud

Fixes issue #3576

* Clouds now take camera position as 3D, not 2D

* Cloud grid filling extracted to gridFilled method

* Clouds detect whether camera is inside cloud

* Camera in cloud changes fog by overriding sky colors
  with cloud color

* Sun, moon and stars can be temporarily disabled
  with setBodiesVisible

* Disabling fog also disables all "inside cloud" behaviors

7 files changed, 84 insertions, 30 deletions

diff --git a/src/client/clientlauncher.cpp b/src/client/clientlauncher.cpp
index 4fc8fb3ee..718255cad 100644
--- a/src/client/clientlauncher.cpp
+++ b/src/client/clientlauncher.cpp
@@ -129,7 +129,7 @@ bool ClientLauncher::run(GameParams &game_params, const Settings &cmd_args)
 		g_menucloudsmgr = RenderingEngine::get_scene_manager()->createNewSceneManager();
 	if (!g_menuclouds)
 		g_menuclouds = new Clouds(g_menucloudsmgr, -1, rand(), 100);
-	g_menuclouds->update(v2f(0, 0), video::SColor(255, 200, 200, 255));
+	g_menuclouds->update(v3f(0, 0, 0), video::SColor(255, 200, 200, 255));
 	scene::ICameraSceneNode* camera;
 	camera = g_menucloudsmgr->addCameraSceneNode(0,
 				v3f(0, 0, 0), v3f(0, 60, 100));
diff --git a/src/clouds.cpp b/src/clouds.cpp
index dd6a2dcbd..eeac774a9 100644
--- a/src/clouds.cpp
+++ b/src/clouds.cpp
@@ -24,6 +24,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "debug.h"
 #include "profiler.h"
 #include "settings.h"
+#include <cmath>
 
 
 // Menu clouds are created later
@@ -31,6 +32,9 @@ class Clouds;
 Clouds *g_menuclouds = NULL;
 irr::scene::ISceneManager *g_menucloudsmgr = NULL;
 
+// Constant for now
+static constexpr const float cloud_size = BS * 64.0f;
+
 static void cloud_3d_setting_changed(const std::string &settingname, void *data)
 {
 	// TODO: only re-read cloud settings, not height or radius
@@ -85,8 +89,6 @@ void Clouds::OnRegisterSceneNode()
 	ISceneNode::OnRegisterSceneNode();
 }
 
-#define MYROUND(x) (x > 0.0 ? (int)x : (int)x - 1)
-
 void Clouds::render()
 {
 
@@ -112,19 +114,19 @@ void Clouds::render()
 		Clouds move from Z+ towards Z-
 	*/
 
-	static const float cloud_size = BS * 64.0f;
-
 	const float cloud_full_radius = cloud_size * m_cloud_radius_i;
 
+	v2f camera_pos_2d(m_camera_pos.X, m_camera_pos.Z);
 	// Position of cloud noise origin from the camera
-	v2f cloud_origin_from_camera_f = m_origin - m_camera_pos;
+	v2f cloud_origin_from_camera_f = m_origin - camera_pos_2d;
 	// The center point of drawing in the noise
 	v2f center_of_drawing_in_noise_f = -cloud_origin_from_camera_f;
 	// The integer center point of drawing in the noise
 	v2s16 center_of_drawing_in_noise_i(
-		MYROUND(center_of_drawing_in_noise_f.X / cloud_size),
-		MYROUND(center_of_drawing_in_noise_f.Y / cloud_size)
+		std::floor(center_of_drawing_in_noise_f.X / cloud_size),
+		std::floor(center_of_drawing_in_noise_f.Y / cloud_size)
 	);
+
 	// The world position of the integer center point of drawing in the noise
 	v2f world_center_of_drawing_in_noise_f = v2f(
 		center_of_drawing_in_noise_i.X * cloud_size,
@@ -172,7 +174,6 @@ void Clouds::render()
 
 	bool *grid = new bool[m_cloud_radius_i * 2 * m_cloud_radius_i * 2];
 
-	float cloud_size_noise = cloud_size / BS / 200;
 
 	for(s16 zi = -m_cloud_radius_i; zi < m_cloud_radius_i; zi++) {
 		u32 si = (zi + m_cloud_radius_i) * m_cloud_radius_i * 2 + m_cloud_radius_i;
@@ -180,19 +181,10 @@ void Clouds::render()
 		for (s16 xi = -m_cloud_radius_i; xi < m_cloud_radius_i; xi++) {
 			u32 i = si + xi;
 
-			v2s16 p_in_noise_i(
+			grid[i] = gridFilled(
 				xi + center_of_drawing_in_noise_i.X,
 				zi + center_of_drawing_in_noise_i.Y
 			);
-
-			float noise = noise2d_perlin(
-					(float)p_in_noise_i.X * cloud_size_noise,
-					(float)p_in_noise_i.Y * cloud_size_noise,
-					m_seed, 3, 0.5);
-			// normalize to 0..1 (given 3 octaves)
-			static const float noise_bound = 1.0f + 0.5f + 0.25f;
-			float density = noise / noise_bound * 0.5f + 0.5f;
-			grid[i] = (density < m_params.density);
 		}
 	}
 
@@ -350,7 +342,7 @@ void Clouds::step(float dtime)
 	m_origin = m_origin + dtime * BS * m_params.speed;
 }
 
-void Clouds::update(v2f camera_p, video::SColorf color_diffuse)
+void Clouds::update(const v3f &camera_p, const video::SColorf &color_diffuse)
 {
 	m_camera_pos = camera_p;
 	m_color.r = MYMIN(MYMAX(color_diffuse.r * m_params.color_bright.getRed(),
@@ -360,6 +352,20 @@ void Clouds::update(v2f camera_p, video::SColorf color_diffuse)
 	m_color.b = MYMIN(MYMAX(color_diffuse.b * m_params.color_bright.getBlue(),
 			m_params.color_ambient.getBlue()), 255) / 255.0f;
 	m_color.a = m_params.color_bright.getAlpha() / 255.0f;
+
+	// is the camera inside the cloud mesh?
+	m_camera_inside_cloud = false; // default
+	if (m_enable_3d) {
+		float camera_height = camera_p.Y;
+		if (camera_height >= m_box.MinEdge.Y &&
+				camera_height <= m_box.MaxEdge.Y) {
+			v2f camera_in_noise;
+			camera_in_noise.X = floor((camera_p.X - m_origin.X) / cloud_size + 0.5);
+			camera_in_noise.Y = floor((camera_p.Z - m_origin.Y) / cloud_size + 0.5);
+			bool filled = gridFilled(camera_in_noise.X, camera_in_noise.Y);
+			m_camera_inside_cloud = filled;
+		}
+	}
 }
 
 void Clouds::readSettings()
@@ -369,3 +375,16 @@ void Clouds::readSettings()
 	m_cloud_radius_i = g_settings->getU16("cloud_radius");
 	m_enable_3d = g_settings->getBool("enable_3d_clouds");
 }
+
+bool Clouds::gridFilled(int x, int y) const
+{
+	float cloud_size_noise = cloud_size / (BS * 200.f);
+	float noise = noise2d_perlin(
+			(float)x * cloud_size_noise,
+			(float)y * cloud_size_noise,
+			m_seed, 3, 0.5);
+	// normalize to 0..1 (given 3 octaves)
+	static constexpr const float noise_bound = 1.0f + 0.5f + 0.25f;
+	float density = noise / noise_bound * 0.5f + 0.5f;
+	return (density < m_params.density);
+}
diff --git a/src/clouds.h b/src/clouds.h
index 52ea930f9..66bd9269c 100644
--- a/src/clouds.h
+++ b/src/clouds.h
@@ -73,7 +73,7 @@ public:
 
 	void step(float dtime);
 
-	void update(v2f camera_p, video::SColorf color);
+	void update(const v3f &camera_p, const video::SColorf &color);
 
 	void updateCameraOffset(v3s16 camera_offset)
 	{
@@ -116,6 +116,10 @@ public:
 		updateBox();
 	}
 
+	bool isCameraInsideCloud() const { return m_camera_inside_cloud; }
+
+	const video::SColor getColor() const { return m_color.toSColor(); }
+
 private:
 	void updateBox()
 	{
@@ -125,17 +129,20 @@ private:
 				BS * 1000000.0f, height_bs + thickness_bs - BS * m_camera_offset.Y, BS * 1000000.0f);
 	}
 
+	bool gridFilled(int x, int y) const;
+
 	video::SMaterial m_material;
 	aabb3f m_box;
 	s16 m_passed_cloud_y;
 	u16 m_cloud_radius_i;
 	bool m_enable_3d;
 	u32 m_seed;
-	v2f m_camera_pos;
+	v3f m_camera_pos;
 	v2f m_origin;
 	v3s16 m_camera_offset;
 	video::SColorf m_color = video::SColorf(1.0f, 1.0f, 1.0f, 1.0f);
 	CloudParams m_params;
+	bool m_camera_inside_cloud = false;
 
 };
 
diff --git a/src/game.cpp b/src/game.cpp
index 9f7b0ca52..b6304f19e 100644
--- a/src/game.cpp
+++ b/src/game.cpp
@@ -4104,12 +4104,29 @@ void Game::updateFrame(ProfilerGraph *graph, RunStats *stats, f32 dtime,
 		Update clouds
 	*/
 	if (clouds) {
-		v3f player_position = player->getPosition();
 		if (sky->getCloudsVisible()) {
 			clouds->setVisible(true);
 			clouds->step(dtime);
-			clouds->update(v2f(player_position.X, player_position.Z),
-				       sky->getCloudColor());
+			// camera->getPosition is not enough for 3rd person views
+			v3f camera_node_position = camera->getCameraNode()->getPosition();
+			v3s16 camera_offset      = camera->getOffset();
+			camera_node_position.X   = camera_node_position.X + camera_offset.X * BS;
+			camera_node_position.Y   = camera_node_position.Y + camera_offset.Y * BS;
+			camera_node_position.Z   = camera_node_position.Z + camera_offset.Z * BS;
+			clouds->update(camera_node_position,
+					sky->getCloudColor());
+			if (clouds->isCameraInsideCloud() && m_cache_enable_fog &&
+					!flags.force_fog_off) {
+				// if inside clouds, and fog enabled, use that as sky
+				// color(s)
+				video::SColor clouds_dark = clouds->getColor()
+						.getInterpolated(video::SColor(255, 0, 0, 0), 0.9);
+				sky->overrideColors(clouds_dark, clouds->getColor());
+				sky->setBodiesVisible(false);
+				runData.fog_range = 20.0f * BS;
+				// do not draw clouds after all
+				clouds->setVisible(false);
+			}
 		} else {
 			clouds->setVisible(false);
 		}
@@ -4221,7 +4238,6 @@ void Game::updateFrame(ProfilerGraph *graph, RunStats *stats, f32 dtime,
 	/*
 		Drawing begins
 	*/
-
 	const video::SColor &skycolor = sky->getSkyColor();
 
 	TimeTaker tt_draw("mainloop: draw");
diff --git a/src/guiEngine.cpp b/src/guiEngine.cpp
index 5f5b4bbff..65ef1605a 100644
--- a/src/guiEngine.cpp
+++ b/src/guiEngine.cpp
@@ -314,7 +314,7 @@ GUIEngine::~GUIEngine()
 void GUIEngine::cloudInit()
 {
 	m_cloud.clouds = new Clouds(m_smgr, -1, rand(), 100);
-	m_cloud.clouds->update(v2f(0, 0), video::SColor(255,200,200,255));
+	m_cloud.clouds->update(v3f(0, 0, 0), video::SColor(255,200,200,255));
 
 	m_cloud.camera = m_smgr->addCameraSceneNode(0,
 				v3f(0,0,0), v3f(0, 60, 100));
diff --git a/src/sky.cpp b/src/sky.cpp
index 463400194..d92697f30 100644
--- a/src/sky.cpp
+++ b/src/sky.cpp
@@ -233,6 +233,10 @@ void Sky::render()
 		vertices[3] = video::S3DVertex(-1, -1.0, 1, 0, 1, 0, c, t, o);
 		driver->drawIndexedTriangleFan(&vertices[0], 4, indices, 2);
 
+		// If sun, moon and stars are (temporarily) disabled, abort here
+		if (!m_bodies_visible)
+			return;
+
 		driver->setMaterial(m_materials[2]);
 
 		// Draw sunrise/sunset horizon glow texture (textures/base/pack/sunrisebg.png)
@@ -412,8 +416,8 @@ void Sky::render()
 		}
 
 		// Draw stars
-		driver->setMaterial(m_materials[1]);
 		do {
+			driver->setMaterial(m_materials[1]);
 			float starbrightness = MYMAX(0, MYMIN(1,
 				(0.285 - fabs(wicked_time_of_day < 0.5 ?
 				wicked_time_of_day : (1.0 - wicked_time_of_day))) * 10));
@@ -501,6 +505,7 @@ void Sky::update(float time_of_day, float time_brightness,
 	m_time_of_day = time_of_day;
 	m_time_brightness = time_brightness;
 	m_sunlight_seen = sunlight_seen;
+	m_bodies_visible = true;
 
 	bool is_dawn = (time_brightness >= 0.20 && time_brightness < 0.35);
 
diff --git a/src/sky.h b/src/sky.h
index 64d2877e5..ed93a9221 100644
--- a/src/sky.h
+++ b/src/sky.h
@@ -64,8 +64,8 @@ public:
 		return m_visible ? m_skycolor : m_fallback_bg_color;
 	}
 
-	bool getCloudsVisible() { return m_clouds_visible && m_clouds_enabled; }
-	const video::SColorf &getCloudColor() { return m_cloudcolor_f; }
+	bool getCloudsVisible() const { return m_clouds_visible && m_clouds_enabled; }
+	const video::SColorf &getCloudColor() const { return m_cloudcolor_f; }
 
 	void setVisible(bool visible) { m_visible = visible; }
 	// Set only from set_sky API
@@ -74,6 +74,12 @@ public:
 	{
 		m_fallback_bg_color = fallback_bg_color;
 	}
+	void overrideColors(const video::SColor &bgcolor, const video::SColor &skycolor)
+	{
+		m_bgcolor = bgcolor;
+		m_skycolor = skycolor;
+	}
+	void setBodiesVisible(bool visible) { m_bodies_visible = visible; }
 
 private:
 	aabb3f m_box;
@@ -128,6 +134,7 @@ private:
 	bool m_clouds_visible; // Whether clouds are disabled due to player underground
 	bool m_clouds_enabled = true; // Initialised to true, reset only by set_sky API
 	bool m_directional_colored_fog;
+	bool m_bodies_visible = true; // sun, moon, stars
 	video::SColorf m_bgcolor_bright_f = video::SColorf(1.0f, 1.0f, 1.0f, 1.0f);
 	video::SColorf m_skycolor_bright_f = video::SColorf(1.0f, 1.0f, 1.0f, 1.0f);
 	video::SColorf m_cloudcolor_bright_f = video::SColorf(1.0f, 1.0f, 1.0f, 1.0f);