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friction testing

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jacob 2024-10-02 14:17:48 -05:00
parent 62df86a66a
commit 2758bdc394
4 changed files with 69 additions and 25 deletions
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2
src/config.h
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@ -31,7 +31,7 @@
#define GAME_FPS 50.0
#define GAME_TIMESCALE 1.0
#define GAME_PHYSICS_SUBSTEPS 4
#define GAME_PHYSICS_SUBSTEPS 16
/* How many ticks back in time should the user blend between?
* <Delay ms> = <USER_INTERP_OFFSET_TICK_RATIO> * <Game tick rate>

3
src/entity.h
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@ -70,7 +70,8 @@ struct contact {
u32 id; /* ID generated during clipping */
f32 starting_separation; /* How far are original points along normal */
f32 accumulated_impulse; /* Accumulated impulse along normal */
f32 normal_impulse; /* Accumulated impulse along normal */
f32 tangent_impulse; /* Accumulated impulse along tangent */
b32 persisted;
};

80
src/game.c
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@ -161,8 +161,8 @@ INTERNAL void spawn_test_entities(void)
entity_enable_prop(e, ENTITY_PROP_PHYSICAL);
e->mass_unscaled = 100;
//e->inertia_unscaled = 25;
e->inertia_unscaled = F32_INFINITY;
e->inertia_unscaled = 25;
//e->inertia_unscaled = F32_INFINITY;
e->linear_ground_friction = 1000;
e->angular_ground_friction = 100;
@ -427,8 +427,8 @@ INTERNAL void create_contact_manifolds(void)
}
if (contact) {
/* Update existing */
contact->accumulated_impulse = 0;
contact->persisted = true;
contact->normal_impulse = 0;
contact->tangent_impulse = 0;
} else {
/* Insert new */
contact = &manifold->contacts[manifold->num_contacts++];
@ -491,7 +491,7 @@ INTERNAL void warm_start_contacts(f32 dt)
(UNUSED)separation;
(UNUSED)dt;
contact->accumulated_impulse = 0;
contact->normal_impulse = 0;
}
}
@ -514,8 +514,8 @@ INTERNAL void solve_collisions(f32 dt, b32 apply_bias)
struct entity *e1 = entity_from_handle(store, manifold->manifold_e1);
struct v2 v0 = e0->linear_velocity;
f32 w0 = e0->angular_velocity;
struct v2 v1 = e1->linear_velocity;
f32 w0 = e0->angular_velocity;
f32 w1 = e1->angular_velocity;
u32 num_contacts = manifold->num_contacts;
@ -536,11 +536,10 @@ INTERNAL void solve_collisions(f32 dt, b32 apply_bias)
f32 inv_i0 = 1.f / i0;
f32 inv_i1 = 1.f / i1;
/* Normal impulse */
struct v2 normal = manifold->manifold_normal;
for (u32 contact_index = 0; contact_index < num_contacts; ++contact_index) {
struct contact *contact = &manifold->contacts[contact_index];
struct v2 p0 = xform_mul_v2(e0_xf, contact->point_local_e0);
struct v2 p1 = xform_mul_v2(e1_xf, contact->point_local_e1);
@ -555,31 +554,72 @@ INTERNAL void solve_collisions(f32 dt, b32 apply_bias)
struct v2 vcp0 = v2_sub(p0, e0_xf.og);
struct v2 vcp1 = v2_sub(p1, e1_xf.og);
struct v2 vel0 = v2_add(e0->linear_velocity, v2_perp_mul(vcp0, e0->angular_velocity));
struct v2 vel1 = v2_add(e1->linear_velocity, v2_perp_mul(vcp1, e1->angular_velocity));
struct v2 vel0 = v2_add(v0, v2_perp_mul(vcp0, w0));
struct v2 vel1 = v2_add(v1, v2_perp_mul(vcp1, w1));
struct v2 vrel = v2_sub(vel0, vel1);
struct v2 idk0 = v2_perp_mul(vcp0, v2_wedge(vcp0, normal) * inv_i0);
struct v2 idk1 = v2_perp_mul(vcp1, v2_wedge(vcp1, normal) * inv_i1);
f32 k = inv_m0 + inv_m1 + v2_dot(normal, v2_add(idk0, idk1));
f32 vcp0_wedge = v2_wedge(vcp0, normal);
f32 vcp1_wedge = v2_wedge(vcp1, normal);
f32 k = (inv_m0 + inv_m1) + (inv_i0 * vcp0_wedge * vcp0_wedge) + (inv_i1 * vcp1_wedge * vcp1_wedge);
k = k > 0.0f ? 1.0f / k : 0.0f;
/* (to be applied along n) */
f32 vn = v2_dot(vrel, normal);
f32 j = (vn + bias) / k;
f32 j = (vn + bias) * k;
j *= inv_num_contacts;
f32 old_accumulated_impulse = contact->accumulated_impulse;
f32 new_accumulated_impulse = max_f32(contact->accumulated_impulse + j, 0);
f32 delta = new_accumulated_impulse - old_accumulated_impulse;
contact->accumulated_impulse = new_accumulated_impulse;
f32 old_impulse = contact->normal_impulse;
f32 new_impulse = max_f32(contact->normal_impulse + j, 0);
f32 delta = new_impulse - old_impulse;
contact->normal_impulse = new_impulse;
struct v2 impulse = v2_mul(normal, delta);
v0 = v2_sub(v0, v2_mul(impulse, inv_m0));
w0 -= v2_wedge(vcp0, impulse) * inv_i0;
v1 = v2_add(v1, v2_mul(impulse, inv_m1));
w0 -= v2_wedge(vcp0, impulse) * inv_i0;
w1 += v2_wedge(vcp1, impulse) * inv_i1;
}
#if 1
/* Tangent impulse */
struct v2 tangent = v2_perp(normal);
for (u32 contact_index = 0; contact_index < num_contacts; ++contact_index) {
struct contact *contact = &manifold->contacts[contact_index];
struct v2 p0 = xform_mul_v2(e0_xf, contact->point_local_e0);
struct v2 p1 = xform_mul_v2(e1_xf, contact->point_local_e1);
struct v2 vcp0 = v2_sub(p0, e0_xf.og);
struct v2 vcp1 = v2_sub(p1, e1_xf.og);
struct v2 vel0 = v2_add(v0, v2_perp_mul(vcp0, w0));
struct v2 vel1 = v2_add(v1, v2_perp_mul(vcp1, w1));
struct v2 vrel = v2_sub(vel0, vel1);
f32 vcp0_wedge = v2_wedge(vcp0, tangent);
f32 vcp1_wedge = v2_wedge(vcp1, tangent);
f32 k = (inv_m0 + inv_m1) + (inv_i0 * vcp0_wedge * vcp0_wedge) + (inv_i1 * vcp1_wedge * vcp1_wedge);
k = k > 0.0f ? 1.0f / k : 0.0f;
/* (to be applied along n) */
f32 vt = v2_dot(vrel, tangent);
float j = vt * k;
//j *= inv_num_contacts;
f32 friction = F32_INFINITY;
f32 max_friction = friction * contact->normal_impulse;
f32 old_impulse = contact->tangent_impulse;
f32 new_impulse = clamp_f32(old_impulse + j, -max_friction, max_friction);
f32 delta = new_impulse - old_impulse;
contact->tangent_impulse = new_impulse;
struct v2 impulse = v2_mul(tangent, delta);
v0 = v2_sub(v0, v2_mul(impulse, inv_m0));
v1 = v2_add(v1, v2_mul(impulse, inv_m1));
w0 -= v2_wedge(vcp0, impulse) * inv_i0;
w1 += v2_wedge(vcp1, impulse) * inv_i1;
}
#endif
e0->linear_velocity = v0;
e0->angular_velocity = w0;
e1->linear_velocity = v1;
@ -1282,7 +1322,6 @@ INTERNAL void game_update(struct game_cmd_array game_cmds)
{
create_contact_manifolds();
//warm_start_contacts(dt);
(UNUSED)create_contact_manifolds;
(UNUSED)solve_collisions;
@ -1292,6 +1331,7 @@ INTERNAL void game_update(struct game_cmd_array game_cmds)
f32 substep_dt = dt / GAME_PHYSICS_SUBSTEPS;
for (u32 i = 0; i < GAME_PHYSICS_SUBSTEPS; ++i) {
#if 1
//warm_start_contacts(dt);
solve_collisions(substep_dt, true);
integrate_positions(substep_dt);
solve_collisions(substep_dt, false); /* Relaxation */

9
src/user.c
View File

@ -1127,7 +1127,8 @@ INTERNAL void user_update(void)
struct v2 point = v2_add(p0, v2_mul(v2_sub(p1, p0), 0.5f));
/* Draw point */
{
u32 color = contact.persisted ? RGBA_32_F(1, 1, 0, 0.50) : RGBA_32_F(1, 0, 0, 0.50);
//u32 color = contact.persisted ? RGBA_32_F(1, 1, 0, 0.50) : RGBA_32_F(1, 0, 0, 0.50);
u32 color = RGBA_32_F(1, 1, 0, 0.50);
//struct v2 point = xform_mul_v2(e0_xf, contact.p0_local);
//struct v2 point = contact.p0_initial_world;
draw_solid_circle(G.viewport_canvas, xform_mul_v2(G.world_view, point), radius, color, 10);
@ -1150,12 +1151,14 @@ INTERNAL void user_update(void)
struct string fmt = STR(
"id: 0x%F\n"
"impulse: %F\n"
"impulse (n): %F\n"
"impulse (t): %F\n"
"separation: %F"
);
struct string text = string_format(temp.arena, fmt,
FMT_HEX(contact.id),
FMT_FLOAT_P(contact.accumulated_impulse, 3),
FMT_FLOAT_P(contact.normal_impulse, 3),
FMT_FLOAT_P(contact.tangent_impulse, 3),
FMT_FLOAT_P(contact.starting_separation, 3));