From: John Tsiombikas <nuclear@member.fsf.org>
Date: Tue, 25 Feb 2020 19:00:06 +0000 (+0200)
Subject: take mass into account
X-Git-Url: http://git.mutantstargoat.com/user/nuclear/?p=dosdemo;a=commitdiff_plain;h=2ee531a10bad1036d2279f9b626da72e345a3b37

take mass into account
---

diff --git a/tools/ropesim/src/main.c b/tools/ropesim/src/main.c
index 3c616f6..f300a57 100644
--- a/tools/ropesim/src/main.c
+++ b/tools/ropesim/src/main.c
@@ -64,11 +64,11 @@ int main(int argc, char **argv)
 	return 0;
 }
 
-#define ROPE_MASSES			5
+#define ROPE_MASSES			10
 #define ROPE_SPRINGS		(ROPE_MASSES - 1)
-#define ROPE_LEN			0.6f
-#define ROPE_MASSES_MASS	0.1f
-#define ROPE_K				80.0f
+#define ROPE_LEN			0.8f
+#define ROPE_MASSES_MASS	0.01f
+#define ROPE_K				180.0f
 
 int init(void)
 {
@@ -106,6 +106,7 @@ int init(void)
 	}
 
 	rsim_init(&rsim);
+	rsim.damping = 0.3;
 	ropes_tail = 0;
 
 	/* anchor points on the inner gimbal */
@@ -243,7 +244,7 @@ void display(void)
 	cmesh_draw(mesh_gin);
 	glPopMatrix();
 
-	cmesh_draw(mesh_suz);
+	/*cmesh_draw(mesh_suz);*/
 
 	glPointSize(7);
 	glBegin(GL_POINTS);
diff --git a/tools/ropesim/src/ropesim.c b/tools/ropesim/src/ropesim.c
index 12c70c4..869d4e9 100644
--- a/tools/ropesim/src/ropesim.c
+++ b/tools/ropesim/src/ropesim.c
@@ -35,15 +35,11 @@ static void step(struct rsim_world *rsim, struct rsim_rope *rope, float dt)
 {
 	int i;
 	float len, fmag;
-	cgm_vec3 npos, force, dir;
+	cgm_vec3 npos, faccel, dir;
 	float inv_damp = rsim->damping == 0.0f ? 1.0f : (1.0f - rsim->damping);
 	struct rsim_mass *mass = rope->masses;
 	struct rsim_spring *spr = rope->springs;
 
-	force.x = rsim->grav.x + rsim->extforce.x;
-	force.y = rsim->grav.y + rsim->extforce.y;
-	force.z = rsim->grav.z + rsim->extforce.z;
-
 	/* accumulate forces from springs */
 	for(i=0; i<rope->num_springs; i++) {
 		dir = spr->mass[1]->p;
@@ -58,9 +54,13 @@ static void step(struct rsim_world *rsim, struct rsim_rope *rope, float dt)
 		}
 		fmag = (len - spr->rest_len) * spr->k;
 
-		cgm_vscale(&dir, fmag);
-		cgm_vadd(&spr->mass[0]->f, &dir);
-		cgm_vsub(&spr->mass[1]->f, &dir);
+		spr->mass[0]->f.x += dir.x * fmag / spr->mass[0]->m;
+		spr->mass[0]->f.y += dir.y * fmag / spr->mass[0]->m;
+		spr->mass[0]->f.z += dir.z * fmag / spr->mass[0]->m;
+
+		spr->mass[1]->f.x -= dir.x * fmag / spr->mass[1]->m;
+		spr->mass[1]->f.y -= dir.y * fmag / spr->mass[1]->m;
+		spr->mass[1]->f.z -= dir.z * fmag / spr->mass[1]->m;
 
 		spr++;
 	}
@@ -73,7 +73,11 @@ static void step(struct rsim_world *rsim, struct rsim_rope *rope, float dt)
 		}
 
 		/* add constant forces to accumulated mass force */
-		cgm_vadd(&mass->f, &force);
+		cgm_vadd(&mass->f, &rsim->grav);
+
+		faccel = rsim->extforce;
+		cgm_vscale(&faccel, 1.0f / mass->m);
+		cgm_vadd(&mass->f, &rsim->extforce);
 
 		mass->v.x = (mass->v.x - mass->v.x * inv_damp * dt) + mass->f.x * dt;
 		mass->v.y = (mass->v.y - mass->v.y * inv_damp * dt) + mass->f.y * dt;