From 9fd675895db99fa368e970eeaae38a4502bb9c30 Mon Sep 17 00:00:00 2001
From: MihailRis <mexaruc@gmail.com>
Date: Sat, 13 Jan 2024 21:20:25 +0300
Subject: [PATCH] physics: step height

---
 src/physics/PhysicsSolver.cpp | 30 ++++++++++++++++++++++++------
 src/physics/PhysicsSolver.h   | 28 +++++++++++++++++-----------
 2 files changed, 41 insertions(+), 17 deletions(-)

diff --git a/src/physics/PhysicsSolver.cpp b/src/physics/PhysicsSolver.cpp
index 2748ffa5..e5a588c9 100644
--- a/src/physics/PhysicsSolver.cpp
+++ b/src/physics/PhysicsSolver.cpp
@@ -36,7 +36,8 @@ void PhysicsSolver::step(
 		
 		vel += gravity * dt * gravityScale;
 		if (collisions) {
-			colisionCalc(chunks, hitbox, vel, pos, half);
+			colisionCalc(chunks, hitbox, vel, pos, half, 
+                         (gravityScale > 0.0f) ? 0.5f : 0.0f);
 		}
 		vel.x *= glm::max(0.0f, 1.0f - dt * linear_damping);
 		vel.z *= glm::max(0.0f, 1.0f - dt * linear_damping);
@@ -78,7 +79,8 @@ void PhysicsSolver::colisionCalc(
 		Hitbox* hitbox, 
 		vec3& vel, 
 		vec3& pos, 
-		const vec3 half)
+		const vec3 half,
+        float stepHeight)
 {
 	// step size (smaller - more accurate, but slower)
 	float s = 2.0f/BLOCK_AABB_GRID;
@@ -86,7 +88,7 @@ void PhysicsSolver::colisionCalc(
 	const AABB* aabb;
 	
 	if (vel.x < 0.0f){
-		for (float y = (pos.y-half.y+E); y <= (pos.y+half.y-E); y+=s){
+		for (float y = (pos.y-half.y+E+stepHeight); y <= (pos.y+half.y-E); y+=s){
 			for (float z = (pos.z-half.z+E); z <= (pos.z+half.z-E); z+=s){
 				float x = (pos.x-half.x-E);
 				if ((aabb = chunks->isObstacleAt(x,y,z))){
@@ -101,7 +103,7 @@ void PhysicsSolver::colisionCalc(
 		}
 	}
 	if (vel.x > 0.0f){
-		for (float y = (pos.y-half.y+E); y <= (pos.y+half.y-E); y+=s){
+		for (float y = (pos.y-half.y+E+stepHeight); y <= (pos.y+half.y-E); y+=s){
 			for (float z = (pos.z-half.z+E); z <= (pos.z+half.z-E); z+=s){
 				float x = (pos.x+half.x+E);
 				if ((aabb = chunks->isObstacleAt(x,y,z))){
@@ -117,7 +119,7 @@ void PhysicsSolver::colisionCalc(
 	}
 
 	if (vel.z < 0.0f){
-		for (float y = (pos.y-half.y+E); y <= (pos.y+half.y-E); y+=s){
+		for (float y = (pos.y-half.y+E+stepHeight); y <= (pos.y+half.y-E); y+=s){
 			for (float x = (pos.x-half.x+E); x <= (pos.x+half.x-E); x+=s){
 				float z = (pos.z-half.z-E);
 				if ((aabb = chunks->isObstacleAt(x,y,z))){
@@ -133,7 +135,7 @@ void PhysicsSolver::colisionCalc(
 	}
 
 	if (vel.z > 0.0f){
-		for (float y = (pos.y-half.y+E); y <= (pos.y+half.y-E); y+=s){
+		for (float y = (pos.y-half.y+E+stepHeight); y <= (pos.y+half.y-E); y+=s){
 			for (float x = (pos.x-half.x+E); x <= (pos.x+half.x-E); x+=s){
 				float z = (pos.z+half.z+E);
 				if ((aabb = chunks->isObstacleAt(x,y,z))){
@@ -164,6 +166,22 @@ void PhysicsSolver::colisionCalc(
 			}
 		}
 	}
+    if (stepHeight > 0.0 && vel.y <= 0.0f){
+		for (float x = (pos.x-half.x+E); x <= (pos.x+half.x-E); x+=s){
+			for (float z = (pos.z-half.z+E); z <= (pos.z+half.z-E); z+=s){
+				float y = (pos.y-half.y+E);
+				if ((aabb = chunks->isObstacleAt(x,y,z))){
+					vel.y *= 0.0f;
+					float newy = floor(y) + aabb->max().y + half.y;
+					if (glm::abs(newy-pos.y) <= MAX_FIX+stepHeight) {
+						pos.y = newy;	
+					}
+					hitbox->grounded = true;
+					break;
+				}
+			}
+		}
+	}
 	if (vel.y > 0.0f){
 		for (float x = (pos.x-half.x+E); x <= (pos.x+half.x-E); x+=s){
 			for (float z = (pos.z-half.z+E); z <= (pos.z+half.z-E); z+=s){
diff --git a/src/physics/PhysicsSolver.h b/src/physics/PhysicsSolver.h
index 6784b417..08bccfca 100644
--- a/src/physics/PhysicsSolver.h
+++ b/src/physics/PhysicsSolver.h
@@ -8,18 +8,24 @@ class Hitbox;
 class Chunks;
 
 class PhysicsSolver {
-	glm::vec3 gravity;
+    glm::vec3 gravity;
 public:
-	PhysicsSolver(glm::vec3 gravity);
-	void step(Chunks* chunks,
-			Hitbox* hitbox,
-			float delta,
-			uint substeps,
-			bool shifting,
-			float gravityScale,
-			bool collisions);
-	void colisionCalc(Chunks* chunks, Hitbox* hitbox, glm::vec3& vel, glm::vec3& pos, const glm::vec3 half);
-	bool isBlockInside(int x, int y, int z, Hitbox* hitbox);
+    PhysicsSolver(glm::vec3 gravity);
+    void step(Chunks* chunks,
+            Hitbox* hitbox,
+            float delta,
+            uint substeps,
+            bool shifting,
+            float gravityScale,
+            bool collisions);
+    void colisionCalc(
+            Chunks* chunks, 
+            Hitbox* hitbox, 
+            glm::vec3& vel, 
+            glm::vec3& pos, 
+            const glm::vec3 half,
+            float stepHeight);
+    bool isBlockInside(int x, int y, int z, Hitbox* hitbox);
 };
 
 #endif /* PHYSICS_PHYSICSSOLVER_H_ */