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//========= Copyright Valve Corporation, All rights reserved. ============//
//
// Purpose:
//
// $NoKeywords: $
//
//=============================================================================//
#include "cbase.h"
#include "particledraw.h"
#include "materialsystem/imesh.h"
// memdbgon must be the last include file in a .cpp file!!!
#include "tier0/memdbgon.h"
//-----------------------------------------------------------------------------
// Sees if the tracer is behind the camera or should be culled
//-----------------------------------------------------------------------------
static bool ClipTracer( const Vector &start, const Vector &delta, Vector &clippedStart, Vector &clippedDelta )
{
// dist1 = start dot forward - origin dot forward
// dist2 = (start + delta ) dot forward - origin dot forward
// in camera space this is -start[2] since origin = 0 and vecForward = (0, 0, -1)
float dist1 = -start[2];
float dist2 = dist1 - delta[2];
// Clipped, skip this tracer
if ( dist1 <= 0 && dist2 <= 0 )
return true;
clippedStart = start;
clippedDelta = delta;
// Needs to be clipped
if ( dist1 <= 0 || dist2 <= 0 )
{
float fraction = dist2 - dist1;
// Too close to clipping plane
if ( fraction < 1e-3 && fraction > -1e-3 )
return true;
fraction = -dist1 / fraction;
if ( dist1 <= 0 )
{
VectorMA( start, fraction, delta, clippedStart );
}
else
{
VectorMultiply( delta, fraction, clippedDelta );
}
}
return false;
}
//-----------------------------------------------------------------------------
// Computes the four verts to draw the tracer with
//-----------------------------------------------------------------------------
bool Tracer_ComputeVerts( const Vector &start, const Vector &delta, float width, Vector *pVerts )
{
Vector clippedStart, clippedDelta;
// Clip the tracer
if ( ClipTracer( start, delta, clippedStart, clippedDelta ) )
return false;
// Figure out direction in camera space of the normal
Vector normal;
CrossProduct( clippedDelta, clippedStart, normal );
// don't draw if they are parallel
float sqLength = DotProduct( normal, normal );
if (sqLength < 1e-3)
return false;
// Resize the normal to be appropriate based on the width
VectorScale( normal, 0.5f * width / sqrt(sqLength), normal );
VectorSubtract( clippedStart, normal, pVerts[0] );
VectorAdd( clippedStart, normal, pVerts[1] );
VectorAdd( pVerts[0], clippedDelta, pVerts[2] );
VectorAdd( pVerts[1], clippedDelta, pVerts[3] );
return true;
}
void Tracer_Draw( CMeshBuilder *pMeshBuilder, Vector& start, Vector& delta, float width, float* color, float startV, float endV )
{
// Clip the tracer
Vector verts[4];
if (!Tracer_ComputeVerts( start, delta, width, verts ))
return;
// NOTE: Gotta get the winding right so it's not backface culled
// (we need to turn of backface culling for these bad boys)
pMeshBuilder->Position3f( verts[0].x, verts[0].y, verts[0].z );
pMeshBuilder->TexCoord2f( 0, 0.0f, startV );
if (color)
{
pMeshBuilder->Color4fv( color );
}
else
{
pMeshBuilder->Color4ub( 255, 255, 255, 255 );
}
pMeshBuilder->AdvanceVertex();
pMeshBuilder->Position3f( verts[1].x, verts[1].y, verts[1].z );
pMeshBuilder->TexCoord2f( 0, 1.0f, startV );
if (color)
{
pMeshBuilder->Color4fv( color );
}
else
{
pMeshBuilder->Color4ub( 255, 255, 255, 255 );
}
pMeshBuilder->AdvanceVertex();
pMeshBuilder->Position3f( verts[3].x, verts[3].y, verts[3].z );
pMeshBuilder->TexCoord2f( 0, 1.0f, endV );
if (color)
pMeshBuilder->Color4fv( color );
else
pMeshBuilder->Color4ub( 255, 255, 255, 255 );
pMeshBuilder->AdvanceVertex();
pMeshBuilder->Position3f( verts[2].x, verts[2].y, verts[2].z );
pMeshBuilder->TexCoord2f( 0, 0.0f, endV );
if (color)
pMeshBuilder->Color4fv( color );
else
pMeshBuilder->Color4ub( 255, 255, 255, 255 );
pMeshBuilder->AdvanceVertex();
}
//-----------------------------------------------------------------------------
// draw a tracer.
//-----------------------------------------------------------------------------
void Tracer_Draw( ParticleDraw* pDraw, Vector& start, Vector& delta, float width, float* color, float startV, float endV )
{
if( !pDraw->GetMeshBuilder() )
return;
Tracer_Draw( pDraw->GetMeshBuilder(), start, delta, width, color, startV, endV );
}
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