Viewmodel Blood Splatter Overlay

Introduction

In this tutorial, we'll be setting up a simple material proxy system that we can use to overlay a blood detail texture onto our viewmodel based on close-quarters combat.

Final results that can be made from this are, for example, hands and weapons covered in goo, acid, blood, water, animated raindrop water normals, and many more visual design elements.

Requirements

• A Source SDK 2013 engine branch mod.
• Beginner/Intermediate knowledge of C++.
• Knowledge and familiarity with textures and materials.

What You Will Learn

• To create a new material proxy system using the $detail parameter.
• To create an overlay of blood onto a viewmodel after shooting flesh or blood materials (NPCs included of course) at close-quarters.

The Implementation

bloodoverlayproxy.cpp

On the client-side, create a file called bloodoverlayproxy.cpp and copypaste the following in it:

//========= Copyright Bernt Andreas Eide, All rights reserved. ============//
//
// Purpose: When you take damage or you damage someone and blood splats on 
//          you then you'll draw that blood on your hands/weapon. (overlay)
//
//=============================================================================//

#include "cbase.h"
#include "materialsystem/imaterialvar.h"
#include "materialsystem/imaterialproxy.h"
#include "baseviewmodel_shared.h"
#include "c_baseplayer.h"
#include "toolframework_client.h"

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

class C_BloodyTextureProxy : public IMaterialProxy
{
public:
	C_BloodyTextureProxy();
	virtual ~C_BloodyTextureProxy();

	virtual bool Init( IMaterial *pMaterial, KeyValues *pKeyValues );
	C_BaseEntity *BindArgToEntity( void *pArg );
	virtual void OnBind( void *pC_BaseEntity );
	virtual void Release() { delete this; }
	IMaterial *GetMaterial();

private:
	IMaterialVar *m_pBlendFactor;
};

//-----------------------------------------------------------------------------
// Purpose: Constructor
//-----------------------------------------------------------------------------
C_BloodyTextureProxy::C_BloodyTextureProxy()
{
	m_pBlendFactor = NULL;
}

//-----------------------------------------------------------------------------
// Purpose: Destructor
//-----------------------------------------------------------------------------
C_BloodyTextureProxy::~C_BloodyTextureProxy()
{
}

//-----------------------------------------------------------------------------
// Purpose: 
//-----------------------------------------------------------------------------
bool C_BloodyTextureProxy::Init( IMaterial *pMaterial, KeyValues *pKeyValues )
{
	bool found;

	m_pBlendFactor = pMaterial->FindVar( "$detailblendfactor", &found, false );
	if ( !found )
		return false;

	return true;
}

//-----------------------------------------------------------------------------
// Purpose: 
//-----------------------------------------------------------------------------
C_BaseEntity *C_BloodyTextureProxy::BindArgToEntity( void *pArg )
{
	IClientRenderable *pRend = (IClientRenderable *)pArg;
	return pRend ? pRend->GetIClientUnknown()->GetBaseEntity() : NULL;
}

//-----------------------------------------------------------------------------
// Purpose: 
//-----------------------------------------------------------------------------
void C_BloodyTextureProxy::OnBind( void *pC_BaseEntity )
{
	if ( !pC_BaseEntity )
		return;

	C_BaseEntity *pEntity = BindArgToEntity( pC_BaseEntity );
	C_BaseViewModel *pViewModel = dynamic_cast<C_BaseViewModel *>( pEntity );
	if ( pViewModel )
	{
		C_BasePlayer *pOwner = ToBasePlayer( pViewModel->GetOwner() );
		if ( pOwner )
			m_pBlendFactor->SetFloatValue( pOwner->m_bShouldDrawBloodOverlay ? 1.0f : 0.0f );
	}

	if ( ToolsEnabled() )
		ToolFramework_RecordMaterialParams( GetMaterial() );
}

//-----------------------------------------------------------------------------
// Purpose: 
//-----------------------------------------------------------------------------
IMaterial *C_BloodyTextureProxy::GetMaterial()
{
	return m_pBlendFactor->GetOwningMaterial();
}

EXPOSE_INTERFACE( C_BloodyTextureProxy, IMaterialProxy, "BloodyTexture" IMATERIAL_PROXY_INTERFACE_VERSION );

c_baseplayer.h

In c_baseplayer.h, inside the public: section, add the following line:

	bool m_bShouldDrawBloodOverlay;

c_baseplayer.cpp

In c_baseplayer.cpp, below RecvPropString( RECVINFO(m_szLastPlaceName) ), add:

		RecvPropBool( RECVINFO(m_bShouldDrawBloodOverlay) ),

Then in the constructor, below ListenForGameEvent( "base_player_teleported" );, add:

	m_bShouldDrawBloodOverlay = false;

player.h

In player.h, inside the public: section, add the following line:

	CNetworkVar( bool, m_bShouldDrawBloodOverlay ); // Have we been hit or have blood splatted on us?

player.cpp

In player.cpp, inside the constructor and below m_bitsDamageType = 0;, add:

	m_bShouldDrawBloodOverlay = false;

At the bottom of the InitialSpawn( void ) function, add:

	m_bShouldDrawBloodOverlay = false; // Reset blood overlay

Then inside IMPLEMENT_SERVERCLASS_ST( CBasePlayer, DT_BasePlayer ), below SendPropString (SENDINFO(m_szLastPlaceName) ),, add:

	SendPropBool( SENDINFO(m_bShouldDrawBloodOverlay) ),

basecombatcharacter.cpp

In basecombatcharacter.cpp, inside the OnTakeDamage_Alive( const CTakeDamageInfo &info ) function above return 1;, add:

	// Handle the viewmodel blood splatter overlay effect here:
	if ( ( info.GetDamageType() & ( DMG_BULLET | DMG_SLASH | DMG_BLAST | DMG_CLUB | DMG_BUCKSHOT ) ) )
	{
		CBasePlayer *pPlayer = UTIL_GetLocalPlayer();
		if ( pPlayer == this )
			pPlayer->m_bShouldDrawBloodOverlay = true;

		pPlayer = ToBasePlayer( info.GetAttacker() );
		if ( pPlayer && ( this->BloodColor() != BLOOD_COLOR_MECH ) )
		{
			if ( pPlayer->GetAbsOrigin().DistTo( this->GetAbsOrigin() ) < 200.0f )
				pPlayer->m_bShouldDrawBloodOverlay = true;
		}
	}

The Materials

Viewmodel VMTs

Now you'll have to edit every single viewmodel .vmt to include the following snippet of code:

"VertexLitGeneric"
{
	...

	"$detail" "detail/blood_detail"
	"$detailblendmode" "2"
	"$detailblendfactor" "0.0"
	"$detailscale" "1.0"

	"Proxies"
	{
		"BloodyTexture"
		{
		}
	}
}

Notice how we're calling for materials/detail/blood_detail.vtf, this is the blood detail texture that gets placed on top of our viewmodel.

Conclusion

Now all that remains is making your own blood detail texture for this, but for convenience/testing sake, you can download the included placeholder texture found in the "External links" section down below.

And that's all there is to it, if set up right you should now be able to see the blood splatter texture appear on your viewmodel based on the snippet of code we placed into basecombatcharacter.cpp.

External links

Download BloodDetailTexture.rar - A placeholder blood detail texture by Ian B.