Launch / step-down changes

- Launch / wall-transfer off of no-physics slopes
- Prevent step down when trying to move upwards
- E-brake enables launching again
- Removed old comment talking about slope nerf

src/p_map.c

@@ -2601,7 +2601,8 @@ boolean P_TryMove(mobj_t *thing, fixed_t x, fixed_t y, boolean allowdropoff)
 						return false; // mobj must lower itself to fit
 					}
 				}
-				else if (!(P_MobjTouchingSectorSpecial(thing, 1, 14, false))) // Step down
+				else if (thing->momz * P_MobjFlip(thing) <= 0 // Step down requires moving down.
+					&& !(P_MobjTouchingSectorSpecial(thing, 1, 14, false)))
 				{
 					// If the floor difference is MAXSTEPMOVE or less, and the sector isn't Section1:14, ALWAYS
 					// step down! Formerly required a Section1:13 sector for the full MAXSTEPMOVE, but no more.

src/p_mobj.c

@@ -1800,8 +1800,7 @@ void P_XYMovement(mobj_t *mo)
 			*/
 		
 		}
-		else if (predictedz - mo->z > abs(slopemom.z/2)
-			&& P_CanApplySlopePhysics(mo, mo->standingslope) == true) // Sryder 2018-11-26: Don't launch here if it's a slope without physics, we stick to those like glue anyway
+		else if (predictedz - mo->z > abs(slopemom.z / 2))
 		{
 			// Now check if we were supposed to stick to this slope
 			//CONS_Printf("%d-%d > %d\n", (predictedz), (mo->z), (slopemom.z/2));

src/p_slopes.c

@@ -928,6 +928,27 @@ boolean P_CanApplySlopePhysics(mobj_t *mo, pslope_t *slope)
 	return true;
 }
 
+// Returns true if we should run slope launch code on an object.
+boolean P_CanApplySlopeLaunch(mobj_t *mo, pslope_t *slope)
+{
+	if (slope == NULL || mo == NULL || P_MobjWasRemoved(mo) == true)
+	{
+		// Invalid input.
+		return false;
+	}
+
+	// No physics slopes are fine to launch off of.
+
+	if (slope->normal.x == 0 && slope->normal.y == 0)
+	{
+		// Flat slope? No such thing, man. No such thing.
+		return false;
+	}
+
+	// We can do slope launching.
+	return true;
+}
+
 //
 // P_QuantizeMomentumToSlope
 //
@@ -963,11 +984,8 @@ void P_ReverseQuantizeMomentumToSlope(vector3_t *momentum, pslope_t *slope)
 // Handles slope ejection for objects
 void P_SlopeLaunch(mobj_t *mo)
 {
-	if (P_CanApplySlopePhysics(mo, mo->standingslope) == true) // If there's physics, time for launching.
+	if (P_CanApplySlopeLaunch(mo, mo->standingslope) == true) // If there's physics, time for launching.
 	{
-		// Double the pre-rotation Z, then halve the post-rotation Z. This reduces the
-		// vertical launch given from slopes while increasing the horizontal launch
-		// given. Good for SRB2's gravity and horizontal speeds.
 		vector3_t slopemom;
 		slopemom.x = mo->momx;
 		slopemom.y = mo->momy;
@@ -1002,7 +1020,7 @@ fixed_t P_GetWallTransferMomZ(mobj_t *mo, pslope_t *slope)
 	vector3_t slopemom, axis;
 	angle_t ang;
 
-	if (P_CanApplySlopePhysics(mo, mo->standingslope) == false)
+	if (P_CanApplySlopeLaunch(mo, mo->standingslope) == false)
 	{
 		return false;
 	}

src/p_slopes.h

@@ -83,6 +83,7 @@ fixed_t P_GetLightZAt(const lightlist_t *light, fixed_t x, fixed_t y);
 
 // Lots of physics-based bullshit
 boolean P_CanApplySlopePhysics(mobj_t *mo, pslope_t *slope);
+boolean P_CanApplySlopeLaunch(mobj_t *mo, pslope_t *slope);
 void P_QuantizeMomentumToSlope(vector3_t *momentum, pslope_t *slope);
 void P_ReverseQuantizeMomentumToSlope(vector3_t *momentum, pslope_t *slope);
 void P_SlopeLaunch(mobj_t *mo);