From: Daniel Karbach <daniel.karbach@localhorst.tv>
Date: Thu, 5 Nov 2015 16:45:01 +0000 (+0100)
Subject: tentative optimization of chunk intersection test
X-Git-Url: https://git.localhorst.tv/?a=commitdiff_plain;h=ee920127d653b8a3cfbee1efefde909ffa177662;p=blank.git

tentative optimization of chunk intersection test

that really gets used a lot °°
---

diff --git a/src/geometry/distance.hpp b/src/geometry/distance.hpp
index d4bec9b..b53fcd7 100644
--- a/src/geometry/distance.hpp
+++ b/src/geometry/distance.hpp
@@ -16,6 +16,10 @@ inline float distance_squared(const glm::vec3 &a, const glm::vec3 &b) noexcept {
 	return length_squared(a - b);
 }
 
+inline float distance(const glm::vec3 &a, const glm::vec3 &b) noexcept {
+	return length(a - b);
+}
+
 template <class T>
 inline bool iszero(const T &v) noexcept {
 	return length_squared(v) < std::numeric_limits<typename T::value_type>::epsilon();
diff --git a/src/geometry/primitive.hpp b/src/geometry/primitive.hpp
index 351a3a4..7da1096 100644
--- a/src/geometry/primitive.hpp
+++ b/src/geometry/primitive.hpp
@@ -20,6 +20,12 @@ struct AABB {
 	glm::vec3 Center() const noexcept {
 		return min + (max - min) * 0.5f;
 	}
+
+	/// return distance between origin and farthest vertex
+	float OriginRadius() const noexcept {
+		glm::vec3 high(glm::max(abs(min), abs(max)));
+		return length(high);
+	}
 };
 
 struct Ray {
diff --git a/src/world/Chunk.hpp b/src/world/Chunk.hpp
index 6e87a09..e8773fa 100644
--- a/src/world/Chunk.hpp
+++ b/src/world/Chunk.hpp
@@ -30,6 +30,8 @@ public:
 	static constexpr int size = side * side * side;
 
 	static AABB Bounds() noexcept { return AABB{ { 0.0f, 0.0f, 0.0f }, ExactLocation::FExtent() }; }
+	static glm::vec3 Center() noexcept { return glm::vec3(8.0f); }
+	static float Radius() noexcept { return 27.71281292110203669632f; /* 16 * √3 */ }
 
 	static constexpr bool InBounds(const ExactLocation::Fine &pos) noexcept {
 		return
diff --git a/src/world/Entity.hpp b/src/world/Entity.hpp
index 3bcc21f..b3eb1f4 100644
--- a/src/world/Entity.hpp
+++ b/src/world/Entity.hpp
@@ -49,7 +49,9 @@ public:
 	void Name(const std::string &n) { name = n; }
 
 	const AABB &Bounds() const noexcept { return bounds; }
-	void Bounds(const AABB &b) noexcept { bounds = b; }
+	// get distance between local origin and farthest vertex
+	float Radius() const noexcept { return radius; }
+	void Bounds(const AABB &b) noexcept { bounds = b; radius = b.OriginRadius(); }
 
 	bool WorldCollidable() const noexcept { return world_collision; }
 	void WorldCollidable(bool b) noexcept { world_collision = b; }
@@ -136,6 +138,7 @@ private:
 	std::string name;
 
 	AABB bounds;
+	float radius;
 	EntityState state;
 
 	/// chunk to model space
diff --git a/src/world/chunk.cpp b/src/world/chunk.cpp
index cedc532..a6f1521 100644
--- a/src/world/chunk.cpp
+++ b/src/world/chunk.cpp
@@ -400,13 +400,20 @@ bool Chunk::Intersection(
 	const glm::mat4 &Mchunk,
 	std::vector<WorldCollision> &col
 ) noexcept {
+	// box's origin relative to the chunk
+	const glm::vec3 box_coords(Mbox[3] - Mchunk[3]);
+	const float box_rad = box.OriginRadius();
+
+	if (distance_squared(box_coords, Center()) > (box_rad + Radius()) * (box_rad + Radius())) {
+		return false;
+	}
+
 	bool any = false;
 	float penetration;
 	glm::vec3 normal;
 
-	if (!blank::Intersection(box, Mbox, Bounds(), Mchunk, penetration, normal)) {
-		return false;
-	}
+	// assume a bounding radius of 2 for blocks
+	constexpr float block_rad = 2.0f;
 	for (int idx = 0, z = 0; z < side; ++z) {
 		for (int y = 0; y < side; ++y) {
 			for (int x = 0; x < side; ++x, ++idx) {
@@ -414,7 +421,11 @@ bool Chunk::Intersection(
 				if (!type.collision || !type.shape) {
 					continue;
 				}
-				if (type.shape->Intersects(Mchunk * ToTransform(RoughLocation::Fine(x, y, z), idx), box, Mbox, penetration, normal)) {
+				const RoughLocation::Fine block_pos(x, y, z);
+				const ExactLocation::Fine block_coords(ToCoords(block_pos));
+				if (distance_squared(box_coords, block_coords) <= (box_rad + block_rad) * (box_rad + block_rad)
+					&& type.shape->Intersects(Mchunk * ToTransform(block_pos, idx), box, Mbox, penetration, normal)
+				) {
 					col.emplace_back(this, idx, penetration, normal);
 					any = true;
 				}
diff --git a/src/world/world.cpp b/src/world/world.cpp
index 51c060c..3a1aac2 100644
--- a/src/world/world.cpp
+++ b/src/world/world.cpp
@@ -33,6 +33,7 @@ Entity::Entity() noexcept
 , id(-1)
 , name("anonymous")
 , bounds()
+, radius(0.0f)
 , state()
 , heading(0.0f, 0.0f, -1.0f)
 , max_vel(5.0f)
@@ -520,10 +521,24 @@ bool World::Intersection(
 }
 
 bool World::Intersection(const Entity &e, const EntityState &s, std::vector<WorldCollision> &col) {
+	// TODO: make special case for entities here and in Chunk::Intersection so entity's bounding radius
+	//       doesn't have to be calculated over and over again (sqrt)
 	AABB box = e.Bounds();
 	glm::ivec3 reference = s.pos.chunk;
 	glm::mat4 M = s.Transform(reference);
-	return Intersection(box, M, reference, col);
+
+	bool any = false;
+	for (Chunk &cur_chunk : chunks) {
+		if (manhattan_radius(cur_chunk.Position() - reference) > 1) {
+			// chunk is not one of the 3x3x3 surrounding the entity
+			// since there's no entity which can extent over 16 blocks, they can be skipped
+			continue;
+		}
+		if (cur_chunk.Intersection(box, M, cur_chunk.Transform(reference), col)) {
+			any = true;
+		}
+	}
+	return any;
 }
 
 bool World::Intersection(