View source for Dynamic RTT shadow angles in Source 2007

[[File:Dynamic_rtt.jpg|thumb|The difference between a mod with this code(shadows facing away from light) and a mod/game without it(shadows directly under entities).]]

==Introduction==
This article explains how to implement dynamic [[Dynamic Shadows|render-to-texture]] shadow angles in both [[Source 2007]] and [[Source_SDK_2013|Source 2013]] mods. Render-to-texture shadows are cast by most non-static [[Entity|renderables]] (dynamic props, players, NPCs, etc.) in the Source Engine. The direction of the shadow they cast is generally given by the {{ent|shadow_control}} entity, but it affects all entities in a level.

In {{l4d|4}}, {{portal2|4}}, {{as|4}}, {{dmmm|4}} and {{mapbase|4}}, the direction of a shadow is calculated on a per-entity basis, and dictated by the closest light to the entity. By using parts of the [[Alien Swarm]] codebase in your mod, along with some custom files (see below), it is possible to implement this feature in [[Source 2007]] as well as [[Source_SDK_2013|Source 2013]]. 

{{bug|This dynamic shadow angle implementation doesn't work correctly, the shadows have lerping issues when standing in between 2 lights.}}

===game/client/worldlight.cpp===
Create a new file in your '''/game/client''' folder called '''worldlight.cpp''', and paste the following code into it.

{{Warning|By using the '''worldlight.cpp''' and or '''worldlight.h''' files in your mod, then I (Saul Rennison) must be attributed as a contributor within your mod credits.}}

<source lang="cpp">
//========= Copyright (C) 2021, CSProMod Team, All rights reserved. =========//
//
// Purpose: Provide world light-related functions to the client
//
// As the engine provides no access to brush/model data (brushdata_t, model_t),
// we hence have no access to dworldlight_t. Therefore, we manually extract the
// world light data from the BSP itself, before entities are initialized on map
// load.
//
// To find the brightest light at a point, all world lights are iterated.
// Lights whose radii do not encompass our sample point are quickly rejected,
// as are lights that are not in our PVS, or visible from the sample point.
// If the sky light is visible from the sample point, then it shall supersede
// all other world lights.
//
// Written: November 2011
// Author: Saul Rennison
//
//===========================================================================//

#include "cbase.h"
#include "bspfile.h"
#include "client_factorylist.h" // FactoryList_Retrieve
#include "eiface.h" // IVEngineServer
#include "filesystem.h"
#include "worldlight.h"

// memdbgon must be the last include file in a .cpp file!!!
#include "tier0/memdbgon.h"

static IVEngineServer *g_pEngineServer = nullptr;

//-----------------------------------------------------------------------------
// Purpose: Calculate intensity ratio for a worldlight by distance
//-----------------------------------------------------------------------------
static float Engine_WorldLightDistanceFalloff( const dworldlight_t *wl, const Vector &delta )
{
	float falloff;

	switch ( wl->type )
	{
	case emit_surface:
		// Cull out stuff that's too far
		if ( wl->radius != 0 )
		{
			if ( DotProduct( delta, delta ) > ( wl->radius * wl->radius ) )
				return 0.0f;
		}

		return InvRSquared( delta );

	case emit_skylight:
		return 1.0f;

	case emit_quakelight:
		// X - r;
		falloff = wl->linear_attn - FastSqrt( DotProduct( delta, delta ) );
		if ( falloff < 0 )
			return 0.0f;

		return falloff;

	case emit_skyambient:
		return 1.0f;

	case emit_point:
	case emit_spotlight: // Directional & positional
		{
			float dist2, dist;

			dist2 = DotProduct( delta, delta );
			dist = FastSqrt( dist2 );

			// Cull out stuff that's too far
			if ( wl->radius != 0 && dist > wl->radius )
				return 0.0f;

			return 1.0f / ( wl->constant_attn + wl->linear_attn * dist + wl->quadratic_attn * dist2 );
		}
	}

	return 1.0f;
}

//-----------------------------------------------------------------------------
// Purpose: Initialize game system and members
//-----------------------------------------------------------------------------
CWorldLights::CWorldLights() : CAutoGameSystem( "World lights" )
{
	m_nWorldLights = 0;
	m_pWorldLights = nullptr;
}

//-----------------------------------------------------------------------------
// Purpose: Clear worldlights, free memory
//-----------------------------------------------------------------------------
void CWorldLights::Clear()
{
	m_nWorldLights = 0;

	if ( m_pWorldLights )
	{
		delete[] m_pWorldLights;
		m_pWorldLights = nullptr;
	}
}

//-----------------------------------------------------------------------------
// Purpose: Get the IVEngineServer, we need this for the PVS functions
//-----------------------------------------------------------------------------
bool CWorldLights::Init()
{
	factorylist_t factories;
	FactoryList_Retrieve( factories );

	if ( ( g_pEngineServer = static_cast<IVEngineServer *>( factories.appSystemFactory( INTERFACEVERSION_VENGINESERVER, nullptr ) ) ) == nullptr )
		return false;

	return true;
}

//-----------------------------------------------------------------------------
// Purpose: Get all world lights from the BSP
//-----------------------------------------------------------------------------
void CWorldLights::LevelInitPreEntity()
{
	// Get the map path
	const char *pszMapName = modelinfo->GetModelName( modelinfo->GetModel( 1 ) );

	// Open map
	FileHandle_t hFile = g_pFullFileSystem->Open( pszMapName, "rb" );
	if ( !hFile )
	{
		Warning( "CWorldLights: Unable to open map\n" );
		return;
	}

	// Read the BSP header. We don't need to do any version checks, etc. as we
	// can safely assume that the engine did this for us
	dheader_t hdr;
	g_pFullFileSystem->Read( &hdr, sizeof( hdr ), hFile );

	// Grab the light lump and seek to it
	lump_t &lightLump = hdr.lumps[LUMP_WORLDLIGHTS];

	// If the worldlights lump is empty, that means theres no normal, LDR lights to extract
	// This can happen when, for example, the map is compiled in HDR mode only
	// So move on to the HDR worldlights lump
	if ( lightLump.filelen == 0 )
	{
		lightLump = hdr.lumps[LUMP_WORLDLIGHTS_HDR];
	}

	// If we can't divide the lump data into a whole number of worldlights,
	// then the BSP format changed and we're unaware
	if ( lightLump.filelen % sizeof( dworldlight_t ) )
	{
		Warning( "CWorldLights: Unknown world light lump\n" );

		// Close file
		g_pFullFileSystem->Close( hFile );
		return;
	}

	g_pFullFileSystem->Seek( hFile, lightLump.fileofs, FILESYSTEM_SEEK_HEAD );

	// Allocate memory for the worldlights
	m_nWorldLights = lightLump.filelen / sizeof( dworldlight_t );
	m_pWorldLights = new dworldlight_t[m_nWorldLights];

	// Read worldlights then close
	g_pFullFileSystem->Read( m_pWorldLights, lightLump.filelen, hFile );
	g_pFullFileSystem->Close( hFile );

	DevMsg( "CWorldLights: Load successful (%d lights at 0x%p)\n", m_nWorldLights, m_pWorldLights );
}

//-----------------------------------------------------------------------------
// Purpose: Find the brightest light source at a point
//-----------------------------------------------------------------------------
bool CWorldLights::GetBrightestLightSource( const Vector &vecPosition, Vector &vecLightPos, Vector &vecLightBrightness )
{
	if ( !m_nWorldLights || !m_pWorldLights )
		return false;

	// Default light position and brightness to zero
	vecLightBrightness.Init();
	vecLightPos.Init();

	// Find the size of the PVS for our current position
	int nCluster = g_pEngineServer->GetClusterForOrigin( vecPosition );
	int nPVSSize = g_pEngineServer->GetPVSForCluster( nCluster, 0, nullptr );

	// Get the PVS at our position
	byte *pvs = new byte[nPVSSize];
	g_pEngineServer->GetPVSForCluster( nCluster, nPVSSize, pvs );

	// Iterate through all the worldlights
	for ( int i = 0; i < m_nWorldLights; ++i )
	{
		dworldlight_t *light = &m_pWorldLights[i];

		// Skip skyambient
		if ( light->type == emit_skyambient )
		{
			//engine->Con_NPrintf( i, "%d: skyambient", i );
			continue;
		}

		// Handle sun
		if ( light->type == emit_skylight )
		{
			// Calculate sun position
			Vector vecAbsStart = vecPosition + Vector( 0, 0, 30 );
			Vector vecAbsEnd = vecAbsStart - ( light->normal * MAX_TRACE_LENGTH );

			trace_t tr;
			UTIL_TraceLine( vecPosition, vecAbsEnd, MASK_OPAQUE, nullptr, COLLISION_GROUP_NONE, &tr );

			// If we didn't hit anything then we have a problem
			if ( !tr.DidHit() )
			{
				//engine->Con_NPrintf( i, "%d: skylight: couldn't touch sky", i );
				continue;
			}

			// If we did hit something, and it wasn't the skybox, then skip
			// this worldlight
			if ( !( tr.surface.flags & SURF_SKY ) && !( tr.surface.flags & SURF_SKY2D ) )
			{
				//engine->Con_NPrintf( i, "%d: skylight: no sight to sun", i );
				continue;
			}

			// Act like we didn't find any valid worldlights, so the shadow
			// manager uses the default shadow direction instead (should be the
			// sun direction)

			delete[] pvs;

			return false;
		}

		// Calculate square distance to this worldlight
		Vector vecDelta = light->origin - vecPosition;
		float flDistSqr = vecDelta.LengthSqr();
		float flRadiusSqr = light->radius * light->radius;

		// Skip lights that are out of our radius
		if ( flRadiusSqr > 0 && flDistSqr >= flRadiusSqr )
		{
			//engine->Con_NPrintf( i, "%d: out-of-radius (dist: %d, radius: %d)", i, sqrt( flDistSqr ), light->radius );
			continue;
		}

		// Is it out of our PVS?
		if ( !g_pEngineServer->CheckOriginInPVS( light->origin, pvs, nPVSSize ) )
		{
			//engine->Con_NPrintf( i, "%d: out of PVS", i );
			continue;
		}

		// Calculate intensity at our position
		float flRatio = Engine_WorldLightDistanceFalloff( light, vecDelta );
		Vector vecIntensity = light->intensity * flRatio;

		// Is this light more intense than the one we already found?
		if ( vecIntensity.LengthSqr() <= vecLightBrightness.LengthSqr() )
		{
			//engine->Con_NPrintf( i, "%d: too dim", i );
			continue;
		}

		// Can we see the light?
		trace_t tr;
		Vector vecAbsStart = vecPosition + Vector( 0, 0, 30 );
		UTIL_TraceLine( vecAbsStart, light->origin, MASK_OPAQUE, nullptr, COLLISION_GROUP_NONE, &tr );

		if ( tr.DidHit() )
		{
			//engine->Con_NPrintf( i, "%d: trace failed", i );
			continue;
		}

		vecLightPos = light->origin;
		vecLightBrightness = vecIntensity;

		//engine->Con_NPrintf( i, "%d: set (%.2f)", i, vecIntensity.Length() );
	}

	delete[] pvs;

	//engine->Con_NPrintf( m_nWorldLights, "result: %d", !vecLightBrightness.IsZero() );
	return !vecLightBrightness.IsZero();
}

//-----------------------------------------------------------------------------
// Singleton accessor
//-----------------------------------------------------------------------------
static CWorldLights s_WorldLights;
CWorldLights *g_pWorldLights = &s_WorldLights;
</source>

===game/client/worldlight.h===
Now create '''worldlight.h''' within '''/game/client''', pasting in the following code:

{{Note|Don’t forget to add these files to your client project}}

<source lang="cpp">
//========= Copyright (C) 2021, CSProMod Team, All rights reserved. =========//
//
// Purpose: Provide world light-related functions to the client
//
// Written: November 2011
// Author: Saul Rennison
//
//===========================================================================//

#ifndef WORLDLIGHT_H
#define WORLDLIGHT_H
#ifdef _WIN32
#pragma once
#endif

#include "igamesystem.h" // CAutoGameSystem

class Vector;
struct dworldlight_t;

//-----------------------------------------------------------------------------
// Purpose: 
//-----------------------------------------------------------------------------
class CWorldLights : public CAutoGameSystem
{
public:
	CWorldLights();
	~CWorldLights() { Clear(); }

	bool GetBrightestLightSource( const Vector &vecPosition, Vector &vecLightPos, Vector &vecLightBrightness );

	// CAutoGameSystem overrides
	bool Init() OVERRIDE;
	void LevelInitPreEntity() OVERRIDE;
	void LevelShutdownPostEntity() OVERRIDE { Clear(); }

private:
	void Clear();

private:
	int m_nWorldLights;
	dworldlight_t *m_pWorldLights;
};

// Singleton accessor
extern CWorldLights *g_pWorldLights;

#endif // WORLDLIGHT_H
</source>

==Updating the client shadow manager==
We will now use the code available in [[Alien Swarm]] to enable dynamic shadow directions.

===game/client/clientshadowmgr.cpp===
Open '''game/client/clientshadowmgr.cpp''' and make the following changes:

At approximately line 83, below:
<source lang="cpp">#include "cmodel.h"</source>
Add:
<source lang="cpp">#include "debugoverlay_shared.h"
#include "worldlight.h"</source>

At approximately line 94, below:
<source lang="cpp">static ConVar r_flashlight_version2( "r_flashlight_version2", "0" );</source>
Add:
<source lang="cpp">
void WorldLightCastShadowCallback( IConVar *pVar, const char *pszOldValue, float flOldValue );
static ConVar r_worldlight_castshadows( "r_worldlight_castshadows", "1", FCVAR_CHEAT, "Allow world lights to cast shadows", true, 0, true, 1, WorldLightCastShadowCallback );
static ConVar r_worldlight_lerptime( "r_worldlight_lerptime", "0.5", FCVAR_CHEAT );
static ConVar r_worldlight_debug( "r_worldlight_debug", "0", FCVAR_CHEAT );
static ConVar r_worldlight_shortenfactor( "r_worldlight_shortenfactor", "2" , FCVAR_CHEAT, "Makes shadows cast from local lights shorter" );
static ConVar r_worldlight_mincastintensity( "r_worldlight_mincastintensity", "0.3", FCVAR_CHEAT, "Minimum brightness of a light to be classed as shadow casting", true, 0, false, 0 );
</source>

At approximately line 794, replace the line:
<source lang="cpp">void ComputeShadowBBox( IClientRenderable *pRenderable, const Vector &vecAbsCenter, float flRadius, Vector *pAbsMins, Vector *pAbsMaxs );</source>
With:
<source lang="cpp">void ComputeShadowBBox( IClientRenderable *pRenderable, ClientShadowHandle_t shadowHandle, const Vector &vecAbsCenter, float flRadius, Vector *pAbsMins, Vector *pAbsMaxs );</source>

At approximately line(s) 803, below:
<source lang="cpp">
void SetShadowsDisabled( bool bDisabled ) 
{ 
	r_shadows_gamecontrol.SetValue( bDisabled != 1 );
}
</source>
Add:
<source lang="cpp">
void SuppressShadowFromWorldLights( bool bSuppress );
void SetShadowFromWorldLightsEnabled( bool bEnabled );
bool IsShadowingFromWorldLights() const { return m_bShadowFromWorldLights; }
</source>

At approximately line 825, below:
<source lang="cpp">Vector2D				m_WorldSize;</source>
Add:
<source lang="cpp">Vector					m_ShadowDir;</source>

At approximately line 829, below:
<source lang="cpp">QAngle					m_LastAngles;</source>
Add:
<source lang="cpp">
Vector					m_CurrentLightPos;	// When shadowing from local lights, stores the position of the currently shadowing light
Vector					m_TargetLightPos;	// When shadowing from local lights, stores the position of the new shadowing light
float					m_LightPosLerp;		// Lerp progress when going from current to target light
</source>

At approximately line 931, below:
<source lang="cpp">const Vector &GetShadowDirection( IClientRenderable *pRenderable ) const;</source>
Add:
<source lang="cpp">const Vector &GetShadowDirection( ClientShadowHandle_t shadowHandle ) const;</source>

At approximately line 966, below:
<source lang="cpp">void	SetViewFlashlightState( int nActiveFlashlightCount, ClientShadowHandle_t* pActiveFlashlights );</source>
Add:
<source lang="cpp">void	UpdateDirtyShadow( ClientShadowHandle_t handle );
void	UpdateShadowDirectionFromLocalLightSource( ClientShadowHandle_t shadowHandle );</source>

At approximately line 994, below:
<source lang="cpp">int m_nMaxDepthTextureShadows;</source>
Add:
<source lang="cpp">bool m_bShadowFromWorldLights;</source>

At approximately line 1114, replace the line:
<source lang="cpp">s_ClientShadowMgr.ComputeShadowBBox( pRenderable, vecAbsCenter, flRadius, &vecAbsMins, &vecAbsMaxs );</source>
With:
<source lang="cpp">s_ClientShadowMgr.ComputeShadowBBox( pRenderable, shadow.m_ShadowHandle, vecAbsCenter, flRadius, &vecAbsMins, &vecAbsMaxs );</source>

At approximately line 1194, below:
<source lang="cpp">m_bThreaded = false;</source>
Add:
<source lang="cpp">m_bShadowFromWorldLights = r_worldlight_castshadows.GetBool();</source>

At approximately line 1853, below:
<source lang="cpp">shadow.m_nRenderFrame = -1;</source>
Add:
<source lang="cpp">
shadow.m_ShadowDir = GetShadowDirection();
shadow.m_CurrentLightPos.Init( FLT_MAX, FLT_MAX, FLT_MAX );
shadow.m_TargetLightPos.Init( FLT_MAX, FLT_MAX, FLT_MAX );
shadow.m_LightPosLerp = FLT_MAX;
</source>

At approximately line 2328, replace the line:
<source lang="cpp">Vector vecShadowDir = GetShadowDirection( pRenderable );</source>
With:
<source lang="cpp">Vector vecShadowDir = GetShadowDirection( handle );</source>

At approximately line 2511, replace the line:
<source lang="cpp">Vector vecShadowDir = GetShadowDirection( pRenderable );</source>
With:
<source lang="cpp">Vector vecShadowDir = GetShadowDirection( handle );</source>

At approximately line 2975, replace the lines:
<source lang="cpp">
Assert( m_Shadows.IsValidIndex( handle ) );
UpdateProjectedTextureInternal( handle, false );
</source>
With:
<source lang="cpp">UpdateDirtyShadow( handle );</source>

At approximately line 3138, replace the line:
<source lang="cpp">if (force || (origin != shadow.m_LastOrigin) || (angles != shadow.m_LastAngles))</source>
With:
<source lang="cpp">if ( force || (origin != shadow.m_LastOrigin) || (angles != shadow.m_LastAngles) || shadow.m_LightPosLerp < 1.0f )</source>

At approximately line 3284, replace the line:
<source lang="cpp">void CClientShadowMgr::ComputeShadowBBox( IClientRenderable *pRenderable, const Vector &vecAbsCenter, float flRadius, Vector *pAbsMins, Vector *pAbsMaxs )</source>
With:
<source lang="cpp">void CClientShadowMgr::ComputeShadowBBox( IClientRenderable *pRenderable, ClientShadowHandle_t shadowHandle, const Vector &vecAbsCenter, float flRadius, Vector *pAbsMins, Vector *pAbsMaxs )</source>

At approximately line 3289, replace the line:
<source lang="cpp">Vector vecShadowDir = GetShadowDirection( pRenderable );</source>
With:
<source lang="cpp">Vector vecShadowDir = GetShadowDirection( shadowHandle );</source>

At approximately line 3387, replace the line:
<source lang="cpp">Vector vecShadowDir = GetShadowDirection( pSourceRenderable );</source>
With:
<source lang="cpp">Vector vecShadowDir = GetShadowDirection( handle );</source>

At approximately line 4222, below:
<source lang="cpp">
	while( pChild )
	{
		if( pChild->GetClientRenderable()==pRenderable )
			return true;

		pChild = pChild->NextMovePeer();
	}

	return false;
}</source>
Add:
<source lang="cpp">
//-----------------------------------------------------------------------------
// Purpose: 
//-----------------------------------------------------------------------------
const Vector &CClientShadowMgr::GetShadowDirection( ClientShadowHandle_t shadowHandle ) const
{
	Assert( shadowHandle != CLIENTSHADOW_INVALID_HANDLE );

	IClientRenderable *pRenderable = ClientEntityList().GetClientRenderableFromHandle( m_Shadows[shadowHandle].m_Entity );
	Assert( pRenderable );

	if ( !IsShadowingFromWorldLights() )
	{
		return GetShadowDirection( pRenderable );
	}

	Vector &vecResult = AllocTempVector();
	vecResult = m_Shadows[shadowHandle].m_ShadowDir;

	// Allow the renderable to override the default
	pRenderable->GetShadowCastDirection( &vecResult, GetActualShadowCastType( pRenderable ) );

	return vecResult;
}

//-----------------------------------------------------------------------------
// Purpose: 
//-----------------------------------------------------------------------------
void CClientShadowMgr::UpdateShadowDirectionFromLocalLightSource( ClientShadowHandle_t shadowHandle )
{
	Assert( shadowHandle != CLIENTSHADOW_INVALID_HANDLE );

	ClientShadow_t &shadow = m_Shadows[shadowHandle];

	IClientRenderable *pRenderable = ClientEntityList().GetClientRenderableFromHandle( shadow.m_Entity );

	// TODO: Figure out why this still gets hit
	Assert( pRenderable );
	if ( !pRenderable )
	{
		DevWarning( "%s(): Skipping shadow with invalid client renderable (shadow handle %d)\n", __FUNCTION__, shadowHandle );
		return;
	}

	Vector bbMin, bbMax;
	pRenderable->GetRenderBoundsWorldspace( bbMin, bbMax );
	Vector origin( 0.5f * ( bbMin + bbMax ) );
	origin.z = bbMin.z; // Putting origin at the bottom of the bounding box makes the shadows a little shorter

	Vector lightPos;
	Vector lightBrightness;

	if ( shadow.m_LightPosLerp >= 1.0f ) // Skip finding new light source if we're in the middle of a lerp
	{
		// Calculate minimum brightness squared
		float flMinBrightnessSqr = r_worldlight_mincastintensity.GetFloat();
		flMinBrightnessSqr *= flMinBrightnessSqr;

		if ( g_pWorldLights->GetBrightestLightSource( pRenderable->GetRenderOrigin(), lightPos, lightBrightness ) == false || lightBrightness.LengthSqr() < flMinBrightnessSqr )
		{
			// Didn't find a light source at all, use default shadow direction
			// TODO: Could switch to using blobby shadow in this case
			lightPos.Init( FLT_MAX, FLT_MAX, FLT_MAX );
		}
	}

	if ( shadow.m_LightPosLerp == FLT_MAX )	// First light pos ever, just init
	{
		shadow.m_CurrentLightPos = lightPos;
		shadow.m_TargetLightPos = lightPos;
		shadow.m_LightPosLerp = 1.0f;
	}
	else if ( shadow.m_LightPosLerp < 1.0f )
	{
		// We're in the middle of a lerp from current to target light. Finish it.
		shadow.m_LightPosLerp += gpGlobals->frametime * 1.0f / r_worldlight_lerptime.GetFloat();
		shadow.m_LightPosLerp = clamp( shadow.m_LightPosLerp, 0.0f, 1.0f );

		Vector currLightPos( shadow.m_CurrentLightPos );
		Vector targetLightPos( shadow.m_TargetLightPos );
		if ( currLightPos.x == FLT_MAX )
		{
			currLightPos = origin - 200.0f * GetShadowDirection();
		}
		if ( targetLightPos.x == FLT_MAX )
		{
			targetLightPos = origin - 200.0f * GetShadowDirection();
		}

		// Lerp light pos
		Vector v1 = origin - shadow.m_CurrentLightPos;
		v1.NormalizeInPlace();

		Vector v2 = origin - shadow.m_TargetLightPos;
		v2.NormalizeInPlace();

		// SAULUNDONE: Caused over top sweeping far too often
#if 0
		if ( v1.Dot( v2 ) < 0.0f )
		{
			// If change in shadow angle is more than 90 degrees, lerp over the renderable's top to avoid long sweeping shadows
			Vector fakeOverheadLightPos( origin.x, origin.y, origin.z + 200.0f );
			if ( shadow.m_LightPosLerp < 0.5f )
			{
				lightPos = Lerp( 2.0f * shadow.m_LightPosLerp, currLightPos, fakeOverheadLightPos );
			}
			else
			{
				lightPos = Lerp( 2.0f * shadow.m_LightPosLerp - 1.0f, fakeOverheadLightPos, targetLightPos );
			}
		}
		else
#endif
		{
			lightPos = Lerp( shadow.m_LightPosLerp, currLightPos, targetLightPos );
		}

		if ( shadow.m_LightPosLerp >= 1.0f )
		{
			shadow.m_CurrentLightPos = shadow.m_TargetLightPos;
		}
	}
	else if ( shadow.m_LightPosLerp >= 1.0f )
	{
		// Check if we have a new closest light position and start a new lerp
		float flDistSq = ( lightPos - shadow.m_CurrentLightPos ).LengthSqr();

		if ( flDistSq > 1.0f )
		{
			// Light position has changed, which means we got a new light source. Initiate a lerp
			shadow.m_TargetLightPos = lightPos;
			shadow.m_LightPosLerp = 0.0f;
		}

		lightPos = shadow.m_CurrentLightPos;
	}

	if ( lightPos.x == FLT_MAX )
	{
		lightPos = origin - 200.0f * GetShadowDirection();
	}

	Vector vecResult( origin - lightPos );
	vecResult.NormalizeInPlace();

	vecResult.z *= r_worldlight_shortenfactor.GetFloat();
	vecResult.NormalizeInPlace();

	shadow.m_ShadowDir = vecResult;

	if ( r_worldlight_debug.GetBool() )
	{
		NDebugOverlay::Line( lightPos, origin, 255, 255, 0, false, 0.0f );
	}
}

//-----------------------------------------------------------------------------
// Purpose: 
//-----------------------------------------------------------------------------
void CClientShadowMgr::UpdateDirtyShadow( ClientShadowHandle_t handle )
{
	Assert( m_Shadows.IsValidIndex( handle ) );
 
	if ( IsShadowingFromWorldLights() )
		UpdateShadowDirectionFromLocalLightSource( handle );
 
	UpdateProjectedTextureInternal( handle, false );
}

//-----------------------------------------------------------------------------
// Purpose: 
//-----------------------------------------------------------------------------
void WorldLightCastShadowCallback( IConVar *pVar, const char *pszOldValue, float flOldValue )
{
	s_ClientShadowMgr.SetShadowFromWorldLightsEnabled( r_worldlight_castshadows.GetBool() );
}

//-----------------------------------------------------------------------------
// Purpose: 
//-----------------------------------------------------------------------------
void CClientShadowMgr::SetShadowFromWorldLightsEnabled( bool bEnabled )
{
	if ( bEnabled == IsShadowingFromWorldLights() )
		return;
 
	m_bShadowFromWorldLights = bEnabled;
	UpdateAllShadows();
}
</source>

==Complete source code of clientshadowmgr.cpp==

See [[Dynamic RTT shadow angles in Source 2007/Clientshadowmgr.cpp]].

==Conclusion==
Now recompile, and dynamically angled shadows should be enabled in your mod. 

Compile errors or incorrect functionality may arise from:
* Not including the '''worldlight.cpp/h''' files in your client project.
* Missing steps. Specifically, double check your '''clientshadowmgr.cpp''' changes.

Happy modding!

[[Category:Tutorials]]
[[Category:Programming]]