// Copyright (C) 2002-2007 Nikolaus Gebhardt
// This file is part of the "Irrlicht Engine".
// For conditions of distribution and use, see copyright notice in irrlicht.h

#include "CShadowVolumeSceneNode.h"
#include "ISceneManager.h"
#include "IMesh.h"
#include "IVideoDriver.h"
#include "SLight.h"

namespace irr
{
namespace scene
{


//! constructor
CShadowVolumeSceneNode::CShadowVolumeSceneNode(ISceneNode* parent,
					ISceneManager* mgr, s32 id,
					bool zfailmethod, f32 infinity)
: IShadowVolumeSceneNode(parent, mgr, id), Indices(0), Vertices(0),
	Adjacency(0), FaceData(0), UseZFailMethod(zfailmethod),
	IndexCountAllocated(0), VertexCountAllocated(0),
	IndexCount(0), VertexCount(0), ShadowVolumesUsed(0),
	Edges(0), EdgeCount(0), Infinity(infinity)
{
	#ifdef _DEBUG
	setDebugName("CShadowVolumeSceneNode");
	#endif

	setAutomaticCulling(scene::EAC_OFF);
}



//! destructor
CShadowVolumeSceneNode::~CShadowVolumeSceneNode()
{
	delete [] Edges;

	for (u32 i=0; i<ShadowVolumes.size(); ++i)
		delete [] ShadowVolumes[i].vertices;

	delete [] Vertices;
	delete [] Indices;
	delete [] Adjacency;
	delete [] FaceData;
}



void CShadowVolumeSceneNode::createShadowVolume(const core::vector3df& light)
{
	SShadowVolume* svp = 0;

	// builds the shadow volume and adds it to the shadow volume list.

	if (ShadowVolumes.size() > (u32)ShadowVolumesUsed)
	{
		// get the next unused buffer
		svp = &ShadowVolumes[ShadowVolumesUsed];
		if (svp->size >= IndexCount*5)
			svp->count = 0;
		else
		{
			svp->size = IndexCount*5;
			svp->count = 0;
			delete [] svp->vertices;
			svp->vertices = new core::vector3df[svp->size];
		}

		++ShadowVolumesUsed;
	}
	else
	{
		// add a buffer
		SShadowVolume tmp;
		// lets make a rather large shadowbuffer
		tmp.size = IndexCount*5;
		tmp.count = 0;
		tmp.vertices = new core::vector3df[tmp.size];
		ShadowVolumes.push_back(tmp);
		svp = &ShadowVolumes[ShadowVolumes.size()-1];
		++ShadowVolumesUsed;
	}

	const s32 faceCount = (s32)(IndexCount / 3);

	if (!Edges || faceCount * 6 > EdgeCount)
	{
		delete [] Edges;
		EdgeCount = faceCount * 6;
		Edges = new u16[EdgeCount];
	}

	s32 numEdges = 0;
	const core::vector3df ls = light * Infinity; // light scaled

	//if (UseZFailMethod)
	//	createZFailVolume(faceCount, numEdges, light, svp);
	//else
	//	createZPassVolume(faceCount, numEdges, light, svp, false);

	// the createZFailVolume does currently not work 100% correctly,
	// so we create createZPassVolume with caps if the zfail method
	// is used
	createZPassVolume(faceCount, numEdges, light, svp, UseZFailMethod);

	for (s32 i=0; i<numEdges; ++i)
	{
		core::vector3df &v1 = Vertices[Edges[2*i+0]];
		core::vector3df &v2 = Vertices[Edges[2*i+1]];
		core::vector3df v3(v1 - ls);
		core::vector3df v4(v2 - ls);

		// Add a quad (two triangles) to the vertex list
		if (svp->vertices && svp->count < svp->size-5)
		{
			svp->vertices[svp->count++] = v1;
			svp->vertices[svp->count++] = v2;
			svp->vertices[svp->count++] = v3;

			svp->vertices[svp->count++] = v2;
			svp->vertices[svp->count++] = v4;
			svp->vertices[svp->count++] = v3;
		}
	}
}


void CShadowVolumeSceneNode::createZFailVolume(s32 faceCount, s32& numEdges,
						const core::vector3df& light,
						SShadowVolume* svp)
{
	s32 i;
	const core::vector3df ls = light * Infinity;

	// Check every face if it is front or back facing the light.
	for (i=0; i<faceCount; ++i)
	{
		const u16 wFace0 = Indices[3*i+0];
		const u16 wFace1 = Indices[3*i+1];
		const u16 wFace2 = Indices[3*i+2];

		const core::vector3df v0 = Vertices[wFace0];
		const core::vector3df v1 = Vertices[wFace1];
		const core::vector3df v2 = Vertices[wFace2];

		if (core::triangle3df(v0,v1,v2).isFrontFacing(light))
		{
			FaceData[i] = false; // it's a back facing face

			if (svp->vertices && svp->count < svp->size-5)
			{
				// add front cap
				svp->vertices[svp->count++] = v0;
				svp->vertices[svp->count++] = v2;
				svp->vertices[svp->count++] = v1;

				// add back cap
				svp->vertices[svp->count++] = v0 - ls;
				svp->vertices[svp->count++] = v1 - ls;
				svp->vertices[svp->count++] = v2 - ls;
			}
		}
		else
			FaceData[i] = true; // it's a front facing face
	}

	for(i=0; i<faceCount; ++i)
	{
		if (FaceData[i] == true)
		{
			const u16 wFace0 = Indices[3*i+0];
			const u16 wFace1 = Indices[3*i+1];
			const u16 wFace2 = Indices[3*i+2];

			const u16 adj0 = Adjacency[3*i+0];
			const u16 adj1 = Adjacency[3*i+1];
			const u16 adj2 = Adjacency[3*i+2];

			if (adj0 != (u16)-1 && FaceData[adj0] == false)
			{
				// add edge v0-v1
				Edges[2*numEdges+0] = wFace0;
				Edges[2*numEdges+1] = wFace1;
				++numEdges;
			}

			if (adj1 != (u16)-1 && FaceData[adj1] == false)
			{
				// add edge v1-v2
				Edges[2*numEdges+0] = wFace1;
				Edges[2*numEdges+1] = wFace2;
				++numEdges;
			}

			if (adj2 != (u16)-1 && FaceData[adj2] == false)
			{
				// add edge v2-v0
				Edges[2*numEdges+0] = wFace2;
				Edges[2*numEdges+1] = wFace0;
				++numEdges;
			}
		}
	}
}


void CShadowVolumeSceneNode::createZPassVolume(s32 faceCount,
						s32& numEdges,
						core::vector3df light,
						SShadowVolume* svp, bool caps)
{
	light *= Infinity;
	if (light == core::vector3df(0,0,0))
		light = core::vector3df(0.0001f,0.0001f,0.0001f);

	for (s32 i=0; i<faceCount; ++i)
	{
		const u16 wFace0 = Indices[3*i+0];
		const u16 wFace1 = Indices[3*i+1];
		const u16 wFace2 = Indices[3*i+2];

		if (core::triangle3df(Vertices[wFace0],Vertices[wFace1],Vertices[wFace2]).isFrontFacing(light))
		{
			Edges[2*numEdges+0] = wFace0;
			Edges[2*numEdges+1] = wFace1;
			++numEdges;

			Edges[2*numEdges+0] = wFace1;
			Edges[2*numEdges+1] = wFace2;
			++numEdges;

			Edges[2*numEdges+0] = wFace2;
			Edges[2*numEdges+1] = wFace0;
			++numEdges;

			if (caps && svp->vertices && svp->count < svp->size-5)
			{
				svp->vertices[svp->count++] = Vertices[wFace0];
				svp->vertices[svp->count++] = Vertices[wFace2];
				svp->vertices[svp->count++] = Vertices[wFace1];

				svp->vertices[svp->count++] = Vertices[wFace0] - light;
				svp->vertices[svp->count++] = Vertices[wFace1] - light;
				svp->vertices[svp->count++] = Vertices[wFace2] - light;
			}
		}
	}
}


//! sets the mesh from which the shadow volume should be generated.
void CShadowVolumeSceneNode::setMeshToRenderFrom(const IMesh* mesh)
{
	ShadowVolumesUsed = 0;

	s32 oldIndexCount = IndexCount;
	s32 oldVertexCount = VertexCount;

	VertexCount = 0;
	IndexCount = 0;

	if (!mesh)
		return;

	// calculate total amount of vertices and indices

	u32 i;
	s32 totalVertices = 0;
	s32 totalIndices = 0;
	u32 bufcnt = mesh->getMeshBufferCount();

	for (i=0; i<bufcnt; ++i)
	{
		const IMeshBuffer* buf = mesh->getMeshBuffer(i);
		totalIndices += buf->getIndexCount();
		totalVertices += buf->getVertexCount();
	}

	// allocate memory if necessary

	if (totalVertices > VertexCountAllocated)
	{
		delete [] Vertices;
		Vertices = new core::vector3df[totalVertices];
		VertexCountAllocated = totalVertices;
	}

	if (totalIndices > IndexCountAllocated)
	{
		delete [] Indices;
		Indices = new u16[totalIndices];
		IndexCountAllocated = totalIndices;

		if (UseZFailMethod)
		{
			delete [] FaceData;
			FaceData = new bool[totalIndices / 3];
		}
	}

	// copy mesh

	for (i=0; i<bufcnt; ++i)
	{
		const IMeshBuffer* buf = mesh->getMeshBuffer(i);

		const u16* idxp = buf->getIndices();
		const u16* idxpend = idxp + buf->getIndexCount();
		for (; idxp!=idxpend; ++idxp)
			Indices[IndexCount++] = *idxp + VertexCount;

		const u32 vtxcnt = buf->getVertexCount();
		for (u32 j=0; j<vtxcnt; ++j)
			Vertices[VertexCount++] = buf->getPosition(j);
	}

	// recalculate adjacency if necessary
	if (oldVertexCount != VertexCount &&
		oldIndexCount != IndexCount && UseZFailMethod)
		calculateAdjacency();

	// create as much shadow volumes as there are lights but
	// do not ignore the max light settings.

	const u32 lights = SceneManager->getVideoDriver()->getDynamicLightCount();
	core::matrix4 mat = Parent->getAbsoluteTransformation();
	const core::vector3df parentpos = Parent->getAbsolutePosition();
	core::vector3df lpos;
	mat.makeInverse();

	// TODO: Only correct for point lights.
	for (i=0; i<lights; ++i)
	{
		const video::SLight& dl = SceneManager->getVideoDriver()->getDynamicLight(i);
		lpos = dl.Position;
		if (dl.CastShadows &&
			fabs((lpos - parentpos).getLengthSQ()) <= (dl.Radius*dl.Radius*4.0f))
		{
			mat.transformVect(lpos);
			createShadowVolume(lpos);
		}
	}
}


//! pre render method
void CShadowVolumeSceneNode::OnRegisterSceneNode()
{
	if (IsVisible)
		SceneManager->registerNodeForRendering(this, scene::ESNRP_SHADOW);

	ISceneNode::OnRegisterSceneNode();
}


//! renders the node.
void CShadowVolumeSceneNode::render()
{
	video::IVideoDriver* driver = SceneManager->getVideoDriver();

	if (!ShadowVolumesUsed || !driver)
		return;

	driver->setTransform(video::ETS_WORLD, Parent->getAbsoluteTransformation());

	for (s32 i=0; i<ShadowVolumesUsed; ++i)
		driver->drawStencilShadowVolume(ShadowVolumes[i].vertices,
			ShadowVolumes[i].count, UseZFailMethod);
}


//! returns the axis aligned bounding box of this node
const core::aabbox3d<f32>& CShadowVolumeSceneNode::getBoundingBox() const
{
	return Box;
}


//! Generates adjacency information based on mesh indices.
void CShadowVolumeSceneNode::calculateAdjacency(f32 epsilon)
{
	delete [] Adjacency;
	Adjacency = new u16[IndexCount];

	epsilon *= epsilon;

	f32 t = 0;

	// go through all faces and fetch their three neighbours
	for (s32 f=0; f<IndexCount; f+=3)
	{
		for (s32 edge = 0; edge<3; ++edge)
		{
			core::vector3df v1 = Vertices[Indices[f+edge]];
			core::vector3df v2 = Vertices[Indices[f+((edge+1)%3)]];

			// now we search an_O_ther _F_ace with these two
			// vertices, which is not the current face.

			s32 of;

			for (of=0; of<IndexCount; of+=3)
				if (of != f)
				{
					s32 cnt1 = 0;
					s32 cnt2 = 0;

					for (s32 e=0; e<3; ++e)
					{
						t = v1.getDistanceFromSQ(Vertices[Indices[of+e]]);
						if (core::iszero(t))
							++cnt1;

						t = v2.getDistanceFromSQ(Vertices[Indices[of+e]]);
						if (core::iszero(t))
							++cnt2;
					}

					if (cnt1 == 1 && cnt2 == 1)
						break;
				}

			if (of == IndexCount)
				Adjacency[f + edge] = f;
			else
				Adjacency[f + edge] = of / 3;
		}
	}
}


} // end namespace scene
} // end namespace irr

