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Alternative code for slipping (#6256)

* Alternative code for slipping

- does not depend on frame rate
- controllable via environment variables for now

* Adjust slipping speed for item entities too.

* Final version of framerate-independent slippery code

* Remove dead code and fix formatting

* getStandingNodePos should only look 0.05 nodes downwards

This ensures that, even if the player is standing on a partially
filled node, this node is used as the standing node and not the
node below it.

Specific use: enables slippery slabs

* Exchange global getStandingPosNode change for local inline change

Reverts previous commit

* Revert the item movement changes

* Slippery nodes now slip over cliffs and edges

Players no longer suddenly stop before falling off.
Also refactored slippery code into getSlipFactor method.

* Slipping over an edge gated by player's is_slipping state

A new flag for just this case, to reduce costly node lookups in
the normal case of leaning over a non-slippery edge.
Public access for consistency and potential future uses.

* Minor code tweaks / cosmetics

* Add temp variable to improve readability and fix indentation issues
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bendeutsch authored and nerzhul committed Aug 26, 2017
1 parent 0e0643d commit fc13c00ef3e9b6f280146f3d77b6659fcc55a13c
Showing with 55 additions and 16 deletions.
  1. +52 −13 src/localplayer.cpp
  2. +3 −3 src/localplayer.h
@@ -656,13 +656,10 @@ void LocalPlayer::applyControl(float dtime, Environment *env)
else
incH = incV = movement_acceleration_default * BS * dtime;

const INodeDefManager *nodemgr = env->getGameDef()->ndef();
Map *map = &env->getMap();
const ContentFeatures &f = nodemgr->get(map->getNodeNoEx(getStandingNodePos()));
bool slippery = (itemgroup_get(f.groups, "slippery") != 0);
float slip_factor = getSlipFactor(env, speedH);
// Accelerate to target speed with maximum increment
accelerateHorizontal(speedH * physics_override_speed,
incH * physics_override_speed, slippery);
incH * physics_override_speed * slip_factor);
accelerateVertical(speedV * physics_override_speed,
incV * physics_override_speed);
}
@@ -702,19 +699,12 @@ v3f LocalPlayer::getEyeOffset() const

// Horizontal acceleration (X and Z), Y direction is ignored
void LocalPlayer::accelerateHorizontal(const v3f &target_speed,
const f32 max_increase, bool slippery)
const f32 max_increase)
{
if (max_increase == 0)
return;

v3f d_wanted = target_speed - m_speed;
if (slippery) {
if (target_speed == v3f())
d_wanted = -m_speed * 0.05f;
else
d_wanted *= 0.1f;
}

d_wanted.Y = 0.0f;
f32 dl = d_wanted.getLength();
if (dl > max_increase)
@@ -1038,3 +1028,52 @@ void LocalPlayer::old_move(f32 dtime, Environment *env, f32 pos_max_d,
m_can_jump = false;
}
}

float LocalPlayer::getSlipFactor(Environment *env, const v3f &speedH)
{

if (!touching_ground)
return 1.0f;

float slip_factor = 1.0f;
// Slip on slippery nodes
const INodeDefManager *nodemgr = env->getGameDef()->ndef();
Map *map = &env->getMap();
const ContentFeatures &f = nodemgr->get(map->getNodeNoEx(
floatToInt(getPosition() - v3f(0, 0.05f * BS, 0), BS)));
int slippery = 0;
if (f.walkable) {
slippery = itemgroup_get(f.groups, "slippery");
} else if (is_slipping) {
// slipping over an edge? Check surroundings for slippery nodes
slippery = 2 << 16; // guard value, bigger than all realistic ones
for (int z = 0; z <= 1; z++) {
for (int x = 0; x <= 1; x++) {
// this should cover all nodes surrounding player position
v3f offset((x - 0.5f) * BS, 0.05f * BS, (z - 0.5f) * BS);
const ContentFeatures &f2 = nodemgr->get(map->getNodeNoEx(
floatToInt(getPosition() - offset, BS)));
if (f2.walkable) {
// find least slippery node we might be standing on
int s = itemgroup_get(f2.groups, "slippery");
if (s < slippery)
slippery = s;
}
}
}
// without any hits, ignore slippery
if (slippery >= (2 << 16))
slippery = 0;
}
if (slippery >= 1) {
if (speedH == v3f(0.0f)) {
slippery = slippery * 2;
}
slip_factor = core::clamp(1.0f / (slippery + 1), 0.001f, 1.0f);
is_slipping = true;
} else {
// remember this to avoid checking the edge case above too often
is_slipping = false;
}
return slip_factor;
}
@@ -60,6 +60,7 @@ class LocalPlayer : public Player
u8 liquid_viscosity = 0;
bool is_climbing = false;
bool swimming_vertical = false;
bool is_slipping = false;

float physics_override_speed = 1.0f;
float physics_override_jump = 1.0f;
@@ -143,11 +144,10 @@ class LocalPlayer : public Player
void setCollisionbox(const aabb3f &box) { m_collisionbox = box; }

private:
// clang-format off
void accelerateHorizontal(const v3f &target_speed, f32 max_increase, bool slippery);
// clang-format on
void accelerateHorizontal(const v3f &target_speed, const f32 max_increase);
void accelerateVertical(const v3f &target_speed, const f32 max_increase);
bool updateSneakNode(Map *map, const v3f &position, const v3f &sneak_max);
float getSlipFactor(Environment *env, const v3f &speedH);

v3f m_position;

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