//-----------------------------------------------------------------------------
//
// $Id$
//
//-----------------------------------------------------------------------------
//
// $Log$
// Revision 1.21  2002/12/02 19:52:05  niceass
// water pressure & shell ejection stuff
//
// Revision 1.20  2002/08/25 07:08:18  niceass
// added "life" setting to func_pressure
//
// Revision 1.19  2002/07/02 07:22:10  niceass
// kill pressures at LCA
//
// Revision 1.18  2002/06/16 20:06:13  jbravo
// Reindented all the source files with "indent -kr -ut -i8 -l120 -lc120 -sob -bad -bap"
//
// Revision 1.17  2002/06/16 19:12:52  jbravo
// Removed the MISSIONPACK ifdefs and missionpack only code.
//
// Revision 1.16  2002/06/09 05:15:40  niceass
// pressure change
//
// Revision 1.15  2002/06/06 01:54:07  niceass
// pressure change
//
// Revision 1.14  2002/05/26 05:14:14  niceass
// pressure stuff
//
// Revision 1.13  2002/05/18 03:55:35  niceass
// many misc. changes
//
// Revision 1.12  2002/05/09 06:42:06  niceass
// New tracers
//
// Revision 1.11  2002/04/29 06:11:56  niceass
// pressure stuff
//
// Revision 1.10  2002/04/23 06:07:23  niceass
// pressure stuff
//
// Revision 1.9  2002/03/31 02:02:15  niceass
// more random shell bouncing
//
// Revision 1.8  2002/03/16 21:49:45  niceass
// All new shell ejection code
//
// Revision 1.7  2002/01/14 01:19:23  niceass
// No more default 800 gravity on items - NiceAss
//
// Revision 1.6  2002/01/11 19:48:29  jbravo
// Formatted the source in non DOS format.
//
// Revision 1.5  2001/12/31 16:28:41  jbravo
// I made a Booboo with the Log tag.
//
//
//-----------------------------------------------------------------------------
// Copyright (C) 1999-2000 Id Software, Inc.
//

// cg_localents.c -- every frame, generate renderer commands for locally
// processed entities, like smoke puffs, gibs, shells, etc.

#include "cg_local.h"

#define	MAX_LOCAL_ENTITIES	512
localEntity_t cg_localEntities[MAX_LOCAL_ENTITIES];
localEntity_t cg_activeLocalEntities;	// double linked list
localEntity_t *cg_freeLocalEntities;	// single linked list

/*
===================
CG_InitLocalEntities

This is called at startup and for tournement restarts
===================
*/
void CG_InitLocalEntities(void)
{
	int i;

	memset(cg_localEntities, 0, sizeof(cg_localEntities));
	cg_activeLocalEntities.next = &cg_activeLocalEntities;
	cg_activeLocalEntities.prev = &cg_activeLocalEntities;
	cg_freeLocalEntities = cg_localEntities;
	for (i = 0; i < MAX_LOCAL_ENTITIES - 1; i++) {
		cg_localEntities[i].next = &cg_localEntities[i + 1];
	}
}

/*
==================
CG_FreeLocalEntity
==================
*/
void CG_FreeLocalEntity(localEntity_t * le)
{
	if (!le->prev) {
		CG_Error("CG_FreeLocalEntity: not active");
	}
	// remove from the doubly linked active list
	le->prev->next = le->next;
	le->next->prev = le->prev;

	// the free list is only singly linked
	le->next = cg_freeLocalEntities;
	cg_freeLocalEntities = le;
}

/*
===================
CG_AllocLocalEntity

Will allways succeed, even if it requires freeing an old active entity
===================
*/
localEntity_t *CG_AllocLocalEntity(void)
{
	localEntity_t *le;

	if (!cg_freeLocalEntities) {
		// no free entities, so free the one at the end of the chain
		// remove the oldest active entity
		CG_FreeLocalEntity(cg_activeLocalEntities.prev);
	}

	le = cg_freeLocalEntities;
	cg_freeLocalEntities = cg_freeLocalEntities->next;

	memset(le, 0, sizeof(*le));

	// link into the active list
	le->next = cg_activeLocalEntities.next;
	le->prev = &cg_activeLocalEntities;
	cg_activeLocalEntities.next->prev = le;
	cg_activeLocalEntities.next = le;
	return le;
}

/*
====================================================================================

FRAGMENT PROCESSING

A fragment localentity interacts with the environment in some way (hitting walls),
or generates more localentities along a trail.

====================================================================================
*/

/*
================
CG_BloodTrail

Leave expanding blood puffs behind gibs
================
*/
void CG_BloodTrail(localEntity_t * le)
{
	int t;
	int t2;
	int step;
	vec3_t newOrigin;
	localEntity_t *blood;

	step = 150;
	t = step * ((cg.time - cg.frametime + step) / step);
	t2 = step * (cg.time / step);

	for (; t <= t2; t += step) {
		CG_EvaluateTrajectory(&le->pos, t, newOrigin);

		blood = CG_SmokePuff(newOrigin, vec3_origin, 20,	// radius
				     1, 1, 1, 1,	// color
				     2000,	// trailTime
				     t,	// startTime
				     0,	// fadeInTime
				     0,	// flags
				     cgs.media.bloodTrailShader);
		// use the optimized version
		blood->leType = LE_FALL_SCALE_FADE;
		// drop a total of 40 units over its lifetime
		blood->pos.trDelta[2] = 40;
	}
}

/*
================
CG_FragmentBounceMark
================
*/
void CG_FragmentBounceMark(localEntity_t * le, trace_t * trace)
{
	int radius;

	if (le->leMarkType == LEMT_BLOOD) {

		radius = 16 + (rand() & 31);
		CG_ImpactMark(cgs.media.bloodMarkShader, trace->endpos, trace->plane.normal, random() * 360,
			      1, 1, 1, 1, qtrue, radius, qfalse);
	} else if (le->leMarkType == LEMT_BURN) {

		radius = 8 + (rand() & 15);
		CG_ImpactMark(cgs.media.burnMarkShader, trace->endpos, trace->plane.normal, random() * 360,
			      1, 1, 1, 1, qtrue, radius, qfalse);
	}

	// don't allow a fragment to make multiple marks, or they
	// pile up while settling
	le->leMarkType = LEMT_NONE;
}

/*
================
CG_FragmentBounceSound
================
*/
void CG_FragmentBounceSound(localEntity_t * le, trace_t * trace)
{
	if (le->leBounceSoundType == LEBS_BLOOD) {
		// half the gibs will make splat sounds
		if (rand() & 1) {
			int r = rand() & 3;
			sfxHandle_t s;

			if (r == 0) {
				s = cgs.media.gibBounce1Sound;
			} else if (r == 1) {
				s = cgs.media.gibBounce2Sound;
			} else {
				s = cgs.media.gibBounce3Sound;
			}
			trap_S_StartSound(trace->endpos, ENTITYNUM_WORLD, CHAN_AUTO, s);
		}
	} else if (le->leBounceSoundType == LEBS_BRASS) {
		// Elder: play bounce sound
		trap_S_StartSound(trace->endpos, ENTITYNUM_WORLD, CHAN_AUTO, cgs.media.sfx_shelltumble);
	}
	// don't allow a fragment to make multiple bounce sounds,
	// or it gets too noisy as they settle
	le->leBounceSoundType = LEBS_NONE;
}

/*
================
CG_ReflectVelocity
================
*/
void CG_ReflectVelocity(localEntity_t * le, trace_t * trace)
{
	vec3_t velocity, normal;
	float dot;
	int hitTime;

	// NiceAss: Make the reflection less perfect (for brass)
	VectorCopy(trace->plane.normal, normal);

	if (le->leFlags == LEF_TUMBLE) {
		normal[0] += crandom() * 0.15;
		normal[1] += crandom() * 0.15;
		normal[2] += crandom() * 0.15;
		VectorNormalize(normal);
	}
	// reflect the velocity on the trace plane
	hitTime = cg.time - cg.frametime + cg.frametime * trace->fraction;
	CG_LE_EvaluateTrajectoryDelta(&le->pos, hitTime, velocity);
	dot = DotProduct(velocity, normal);
	VectorMA(velocity, -2 * dot, normal, le->pos.trDelta);

	VectorScale(le->pos.trDelta, le->bounceFactor, le->pos.trDelta);

	VectorCopy(trace->endpos, le->pos.trBase);
	le->pos.trTime = cg.time;

	// check for stop, making sure that even on low FPS systems it doesn't bobble
	if (trace->allsolid || VectorLength(le->pos.trDelta) < 30.0) {
		// NiceAss: I don't know what this crap is, but it didn't work too well on sloped surfaces
		/*( trace->plane.normal[2] > 0 && 
		   ( le->pos.trDelta[2] < 40 || le->pos.trDelta[2] < -cg.frametime * le->pos.trDelta[2] ) ) ) {
		 */
		le->pos.trType = TR_STATIONARY;
	}
}

/*
================
CG_AddFragment
================
*/
void CG_AddFragment(localEntity_t * le)
{
	vec3_t newOrigin;
	trace_t trace;

	if (le->pos.trType == TR_STATIONARY) {
		// sink into the ground if near the removal time
		int t;
		float oldZ;

		t = le->endTime - cg.time;
		if (t < SINK_TIME) {
			// we must use an explicit lighting origin, otherwise the
			// lighting would be lost as soon as the origin went
			// into the ground
			VectorCopy(le->refEntity.origin, le->refEntity.lightingOrigin);
			le->refEntity.renderfx |= RF_LIGHTING_ORIGIN;
			oldZ = le->refEntity.origin[2];
			le->refEntity.origin[2] -= 16 * (1.0 - (float) t / SINK_TIME);
			trap_R_AddRefEntityToScene(&le->refEntity);
			le->refEntity.origin[2] = oldZ;
		} else {
			trap_R_AddRefEntityToScene(&le->refEntity);
		}

		return;
	}
	// calculate new position
	CG_LE_EvaluateTrajectory(&le->pos, cg.time, newOrigin);

	// trace a line from previous position to new position
	CG_Trace(&trace, le->refEntity.origin, NULL, NULL, newOrigin, -1, CONTENTS_SOLID);
	if (trace.fraction == 1.0) {
		// still in free fall
		VectorCopy(newOrigin, le->refEntity.origin);

		if (le->leFlags & LEF_TUMBLE) {
			vec3_t angles;

			CG_LE_EvaluateTrajectory(&le->angles, cg.time, angles);
			AnglesToAxis(angles, le->refEntity.axis);
		}

		trap_R_AddRefEntityToScene(&le->refEntity);

		// add a blood trail
		if (le->leBounceSoundType == LEBS_BLOOD) {
			CG_BloodTrail(le);
		}

		return;
	}
	// if it is in a nodrop zone, remove it
	// this keeps gibs from waiting at the bottom of pits of death
	// and floating levels
	if ( CG_PointContents( trace.endpos, 0 ) & CONTENTS_NODROP ) {
		CG_FreeLocalEntity(le);
		return;
	}
	// leave a mark
	CG_FragmentBounceMark(le, &trace);

	// do a bouncy sound
	CG_FragmentBounceSound(le, &trace);

	// reflect the velocity on the trace plane
	CG_ReflectVelocity(le, &trace);

	trap_R_AddRefEntityToScene(&le->refEntity);
}

/*
=====================================================================

TRIVIAL LOCAL ENTITIES

These only do simple scaling or modulation before passing to the renderer
=====================================================================
*/

/*
====================
CG_AddFadeRGB
====================
*/
void CG_AddFadeRGB(localEntity_t * le)
{
	refEntity_t *re;
	float c;

	re = &le->refEntity;

	c = (le->endTime - cg.time) * le->lifeRate;
	c *= 0xff;

	re->shaderRGBA[0] = le->color[0] * c;
	re->shaderRGBA[1] = le->color[1] * c;
	re->shaderRGBA[2] = le->color[2] * c;
	re->shaderRGBA[3] = le->color[3] * c;

	trap_R_AddRefEntityToScene(re);
}

/*
==================
CG_AddMoveScaleFade
==================
*/
static void CG_AddMoveScaleFade(localEntity_t * le)
{
	refEntity_t *re;
	float c;
	vec3_t delta;
	float len;

	re = &le->refEntity;

	if (le->fadeInTime > le->startTime && cg.time < le->fadeInTime) {
		// fade / grow time
		c = 1.0 - (float) (le->fadeInTime - cg.time) / (le->fadeInTime - le->startTime);
	} else {
		// fade / grow time
		c = (le->endTime - cg.time) * le->lifeRate;
	}

	re->shaderRGBA[3] = 0xff * c * le->color[3];

	if (!(le->leFlags & LEF_PUFF_DONT_SCALE)) {
		re->radius = le->radius * (1.0 - c) + 8;
	}

	CG_EvaluateTrajectory(&le->pos, cg.time, re->origin);

	// if the view would be "inside" the sprite, kill the sprite
	// so it doesn't add too much overdraw
	VectorSubtract(re->origin, cg.refdef.vieworg, delta);
	len = VectorLength(delta);
	if (len < le->radius) {
		CG_FreeLocalEntity(le);
		return;
	}

	trap_R_AddRefEntityToScene(re);
}

/*
===================
CG_AddScaleFade

For rocket smokes that hang in place, fade out, and are
removed if the view passes through them.
There are often many of these, so it needs to be simple.
===================
*/
static void CG_AddScaleFade(localEntity_t * le)
{
	refEntity_t *re;
	float c;
	vec3_t delta;
	float len;

	re = &le->refEntity;

	// fade / grow time
	c = (le->endTime - cg.time) * le->lifeRate;

	re->shaderRGBA[3] = 0xff * c * le->color[3];
	re->radius = le->radius * (1.0 - c) + 8;

	// if the view would be "inside" the sprite, kill the sprite
	// so it doesn't add too much overdraw
	VectorSubtract(re->origin, cg.refdef.vieworg, delta);
	len = VectorLength(delta);
	if (len < le->radius) {
		CG_FreeLocalEntity(le);
		return;
	}

	trap_R_AddRefEntityToScene(re);
}

/*
=================
CG_AddFallScaleFade

This is just an optimized CG_AddMoveScaleFade
For blood mists that drift down, fade out, and are
removed if the view passes through them.
There are often 100+ of these, so it needs to be simple.
=================
*/
static void CG_AddFallScaleFade(localEntity_t * le)
{
	refEntity_t *re;
	float c;
	vec3_t delta;
	float len;

	re = &le->refEntity;

	// fade time
	c = (le->endTime - cg.time) * le->lifeRate;

	re->shaderRGBA[3] = 0xff * c * le->color[3];

	re->origin[2] = le->pos.trBase[2] - (1.0 - c) * le->pos.trDelta[2];

	re->radius = le->radius * (1.0 - c) + 16;

	// if the view would be "inside" the sprite, kill the sprite
	// so it doesn't add too much overdraw
	VectorSubtract(re->origin, cg.refdef.vieworg, delta);
	len = VectorLength(delta);
	if (len < le->radius) {
		CG_FreeLocalEntity(le);
		return;
	}

	trap_R_AddRefEntityToScene(re);
}

/*
================
CG_AddExplosion
================
*/
static void CG_AddExplosion(localEntity_t * ex)
{
	refEntity_t *ent;

	ent = &ex->refEntity;

	// add the entity
	trap_R_AddRefEntityToScene(ent);

	// add the dlight
	if (ex->light) {
		float light;

		light = (float) (cg.time - ex->startTime) / (ex->endTime - ex->startTime);
		if (light < 0.5) {
			light = 1.0;
		} else {
			light = 1.0 - (light - 0.5) * 2;
		}
		light = ex->light * light;
		trap_R_AddLightToScene(ent->origin, light, ex->lightColor[0], ex->lightColor[1], ex->lightColor[2]);
	}
}

/*
================
CG_AddSpriteExplosion
================
*/
static void CG_AddSpriteExplosion(localEntity_t * le)
{
	refEntity_t re;
	float c;

	re = le->refEntity;

	c = (le->endTime - cg.time) / (float) (le->endTime - le->startTime);
	if (c > 1) {
		c = 1.0;	// can happen during connection problems
	}

	re.shaderRGBA[0] = 0xff;
	re.shaderRGBA[1] = 0xff;
	re.shaderRGBA[2] = 0xff;
	re.shaderRGBA[3] = 0xff * c * 0.33;

	re.reType = RT_SPRITE;
	re.radius = 42 * (1.0 - c) + 30;

	trap_R_AddRefEntityToScene(&re);

	// add the dlight
	if (le->light) {
		float light;

		light = (float) (cg.time - le->startTime) / (le->endTime - le->startTime);
		if (light < 0.5) {
			light = 1.0;
		} else {
			light = 1.0 - (light - 0.5) * 2;
		}
		light = le->light * light;
		trap_R_AddLightToScene(re.origin, light, le->lightColor[0], le->lightColor[1], le->lightColor[2]);
	}
}

/*
===================
CG_AddScorePlum
===================
*/
#define NUMBER_SIZE		8

void CG_AddScorePlum(localEntity_t * le)
{
	refEntity_t *re;
	vec3_t origin, delta, dir, vec, up = { 0, 0, 1 };
	float c, len;
	int i, score, digits[10], numdigits, negative;

	re = &le->refEntity;

	c = (le->endTime - cg.time) * le->lifeRate;

	score = le->radius;
	if (score < 0) {
		re->shaderRGBA[0] = 0xff;
		re->shaderRGBA[1] = 0x11;
		re->shaderRGBA[2] = 0x11;
	} else {
		re->shaderRGBA[0] = 0xff;
		re->shaderRGBA[1] = 0xff;
		re->shaderRGBA[2] = 0xff;
		if (score >= 50) {
			re->shaderRGBA[1] = 0;
		} else if (score >= 20) {
			re->shaderRGBA[0] = re->shaderRGBA[1] = 0;
		} else if (score >= 10) {
			re->shaderRGBA[2] = 0;
		} else if (score >= 2) {
			re->shaderRGBA[0] = re->shaderRGBA[2] = 0;
		}

	}
	if (c < 0.25)
		re->shaderRGBA[3] = 0xff * 4 * c;
	else
		re->shaderRGBA[3] = 0xff;

	re->radius = NUMBER_SIZE / 2;

	VectorCopy(le->pos.trBase, origin);
	origin[2] += 110 - c * 100;

	VectorSubtract(cg.refdef.vieworg, origin, dir);
	CrossProduct(dir, up, vec);
	VectorNormalize(vec);

	VectorMA(origin, -10 + 20 * sin(c * 2 * M_PI), vec, origin);

	// if the view would be "inside" the sprite, kill the sprite
	// so it doesn't add too much overdraw
	VectorSubtract(origin, cg.refdef.vieworg, delta);
	len = VectorLength(delta);
	if (len < 20) {
		CG_FreeLocalEntity(le);
		return;
	}

	negative = qfalse;
	if (score < 0) {
		negative = qtrue;
		score = -score;
	}

	for (numdigits = 0; !(numdigits && !score); numdigits++) {
		digits[numdigits] = score % 10;
		score = score / 10;
	}

	if (negative) {
		digits[numdigits] = 10;
		numdigits++;
	}

	for (i = 0; i < numdigits; i++) {
		VectorMA(origin, (float) (((float) numdigits / 2) - i) * NUMBER_SIZE, vec, re->origin);
		re->customShader = cgs.media.numberShaders[digits[numdigits - 1 - i]];
		trap_R_AddRefEntityToScene(re);
	}
}

void CG_AddPressureEntity(localEntity_t * le)
{
	vec3_t velocity;
//	vec3_t origin;
	float alpha;

	// Kill it if LCA.
	if (cg.lca)
		CG_FreeLocalEntity(le);

	alpha = -(cg.time - le->startTime) + (le->endTime - le->startTime);
	alpha /= (le->endTime - le->startTime);

	//steamSound!!!

	// steam:
	if ( le->leFlags != LEF_AIR && le->leFlags != LEF_WATER ) {
		VectorScale(le->pos.trDelta, le->size + rand() % 30, velocity);

		velocity[0] += rand() % 40 - 20;
		velocity[1] += rand() % 40 - 20;
	} else
		VectorScale(le->pos.trDelta, le->size, velocity);

//	VectorCopy(le->pos.trBase, origin);

	if (le->leFlags == LEF_AIR)
		CG_ParticleAir(le->pos.trBase, velocity, le->life + rand() % 120, alpha, 2, 1);
	else if (le->leFlags == LEF_FLAME)
		CG_ParticleSteam(le->pos.trBase, velocity, le->life + rand() % 120, alpha, 2, 1,
				cgs.media.flamePressureShader);
	else if (le->leFlags == LEF_WATER)
		CG_ParticleWater(le->pos.trBase, velocity, le->life + rand() % 120, alpha, 1, 2);
	else
		CG_ParticleSteam(le->pos.trBase, velocity, le->life + rand() % 120, alpha, 2, 1, 
				cgs.media.smokePuffShader);
}

/*
================
CG_AddMovingTracer
	- NiceAss
================
*/
void CG_AddTracer(localEntity_t * le)
{
	vec3_t start, end, dir;

	//BG_EvaluateTrajectory( &le->pos, cg.time, start );
	VectorMA(le->pos.trBase, (cg.time - le->pos.trTime) / 1000.0f, le->pos.trDelta, start);

	VectorNormalize2(le->pos.trDelta, dir);
	VectorMA(start, cg_tracerLength.value, dir, end);

	CG_Tracer(start, end);
}

//==============================================================================

/*
===================
CG_AddLocalEntities

===================
*/
void CG_AddLocalEntities(void)
{
	localEntity_t *le, *next;

	// walk the list backwards, so any new local entities generated
	// (trails, marks, etc) will be present this frame
	le = cg_activeLocalEntities.prev;
	for (; le != &cg_activeLocalEntities; le = next) {
		// grab next now, so if the local entity is freed we
		// still have it
		next = le->prev;

		if (cg.time >= le->endTime) {
			CG_FreeLocalEntity(le);
			continue;
		}
		switch (le->leType) {
		default:
			CG_Error("Bad leType: %i", le->leType);
			break;

		case LE_MARK:
			break;

		case LE_TRACER:
			CG_AddTracer(le);
			break;

		case LE_SPRITE_EXPLOSION:
			CG_AddSpriteExplosion(le);
			break;

		case LE_EXPLOSION:
			CG_AddExplosion(le);
			break;

		case LE_FRAGMENT:	// gibs and brass
			CG_AddFragment(le);
			break;

		case LE_MOVE_SCALE_FADE:	// water bubbles
			CG_AddMoveScaleFade(le);
			break;

		case LE_FADE_RGB:	// teleporters, railtrails
			CG_AddFadeRGB(le);
			break;

		case LE_FALL_SCALE_FADE:	// gib blood trails
			CG_AddFallScaleFade(le);
			break;

		case LE_SCALE_FADE:	// rocket trails
			CG_AddScaleFade(le);
			break;

		case LE_SCOREPLUM:
			CG_AddScorePlum(le);
			break;

		case LE_PRESSURE:
			CG_AddPressureEntity(le);
		}
	}
}

/*
	The only difference is that this will account for water friction
*/
void CG_LE_EvaluateTrajectory(const trajectory_t * tr, int atTime, vec3_t result)
{
	float deltaTime;
	float phase;
	float friction = 1.0f;

	switch (tr->trType) {
	case TR_STATIONARY:
	case TR_INTERPOLATE:
		VectorCopy(tr->trBase, result);
		break;
	case TR_LINEAR:
		deltaTime = (atTime - tr->trTime) * 0.001;	// milliseconds to seconds
		VectorMA(tr->trBase, deltaTime, tr->trDelta, result);
		break;
	case TR_SINE:
		deltaTime = (atTime - tr->trTime) / (float) tr->trDuration;
		phase = sin(deltaTime * M_PI * 2);
		VectorMA(tr->trBase, phase, tr->trDelta, result);
		break;
	case TR_LINEAR_STOP:
		if (atTime > tr->trTime + tr->trDuration) {
			atTime = tr->trTime + tr->trDuration;
		}
		deltaTime = (atTime - tr->trTime) * 0.001;	// milliseconds to seconds
		if (deltaTime < 0) {
			deltaTime = 0;
		}
		VectorMA(tr->trBase, deltaTime, tr->trDelta, result);
		break;
	case TR_GRAVITY:
		if (trap_CM_PointContents(tr->trBase, 0) & CONTENTS_WATER)
			friction = 0.3f;
		deltaTime = (atTime - tr->trTime) * 0.001;	// milliseconds to seconds
		VectorMA(tr->trBase, deltaTime * friction, tr->trDelta, result);
		result[2] -= 0.5 * cg_gravity.value * friction * deltaTime * deltaTime;
		break;
	default:
		Com_Error(ERR_DROP, "CG_LE_EvaluateTrajectory: unknown trType: %i", tr->trTime);
		break;
	}
}

void CG_LE_EvaluateTrajectoryDelta(const trajectory_t * tr, int atTime, vec3_t result)
{
	float deltaTime;
	float phase;
	float friction = 1.0f;

	switch (tr->trType) {
	case TR_STATIONARY:
	case TR_INTERPOLATE:
		VectorClear(result);
		break;
	case TR_LINEAR:
		VectorCopy(tr->trDelta, result);
		break;
	case TR_SINE:
		deltaTime = (atTime - tr->trTime) / (float) tr->trDuration;
		phase = cos(deltaTime * M_PI * 2);	// derivative of sin = cos
		phase *= 0.5;
		VectorScale(tr->trDelta, phase, result);
		break;
	case TR_LINEAR_STOP:
		if (atTime > tr->trTime + tr->trDuration) {
			VectorClear(result);
			return;
		}
		VectorCopy(tr->trDelta, result);
		break;
	case TR_GRAVITY:
		if (trap_CM_PointContents(tr->trBase, 0) & CONTENTS_WATER)
			friction = 0.3f;
		deltaTime = (atTime - tr->trTime) * 0.001;	// milliseconds to seconds
		VectorScale(tr->trDelta, friction, result);
		result[2] -= cg_gravity.value * friction * deltaTime;
		break;
	default:
		Com_Error(ERR_DROP, "CG_LE_EvaluateTrajectoryDelta: unknown trType: %i", tr->trTime);
		break;
	}
}