/*  Starshatter: The Open Source Project
    Copyright (c) 2021-2024, Starshatter: The Open Source Project Contributors
    Copyright (c) 2011-2012, Starshatter OpenSource Distribution Contributors
    Copyright (c) 1997-2006, Destroyer Studios LLC.

    AUTHOR:       John DiCamillo


    OVERVIEW
    ========
*/

#include "Terrain.h"
#include "TerrainLayer.h"
#include "TerrainPatch.h"
#include "TerrainRegion.h"
#include "Sim.h"

#include "Light.h"
#include "CameraView.h"
#include "Projector.h"
#include "Bitmap.h"
#include "Game.h"
#include "Scene.h"
#include "Water.h"

// +====================================================================+

// #define DEBUG_DETAIL 1

// +====================================================================+

const int MAX_DETAIL       =  4;
const int PATCH_SIZE       = 17;
const int HALF_PATCH_SIZE  =  8;
const int MAX_VERTS        = PATCH_SIZE * PATCH_SIZE;

static bool illuminating   = false;

// +--------------------------------------------------------------------+

TerrainPatch::TerrainPatch(Terrain* terr,const Bitmap* patch, const Rect& r,
const Point&  p1,    const Point& p2)
: ndetail(0), terrain(terr), rect(r), water(0), min_height(1e9), max_height(-1e9)
{
    luminous   = true;   // we will do our own lighting
    own_model  = false;  // manage the model lifetimes in this derived class

    max_detail = Terrain::DetailLevel();
    scale      = fabs(p1.x - p2.x) / (PATCH_SIZE-1);
    mtnscale   = p2.y - p1.y;
    base       = p1.y;
    size       = p2.x - p1.x;

    ZeroMemory(detail_levels, sizeof(detail_levels));

    terrain_width = patch->Width();

    loc   = (p1 + p2) * 0.5;
    loc.y = base;

    radius    = (float) (size * 0.75);
    heights   = new float[MAX_VERTS];

    float* pHeight = heights;
    int    tscale  = rect.w / (PATCH_SIZE-1);
    int    i, j;

    for (i = 0; i < PATCH_SIZE; i++) {
        int ty = rect.y + i * tscale;

        if (ty < 0)
        ty = 0;

        if (ty > patch->Height()-1)
        ty = patch->Height()-1;

        for (j = 0; j < PATCH_SIZE; j++) {
            int tx = rect.x + (PATCH_SIZE-1 - j) * tscale;

            if (tx < 0)
            tx = 0;

            if (tx > patch->Width()-1)
            tx = patch->Width()-1;

            int   red = patch->GetColor(tx,ty).Red();
            float alt = (float) (red * mtnscale);

            if (alt < min_height)
            min_height = alt;
            if (alt > max_height)
            max_height = alt;

            if (terrain->WaterTexture() && red < 2)
            alt = -5000.0f;

            *pHeight++ = alt;
        }
    }

    Material* mtl = new Material;
    mtl->Ka = ColorValue(0.5f, 0.5f, 0.5f);
    mtl->Kd = ColorValue(0.3f, 0.6f, 0.2f);
    mtl->Ks = Color::Black;

    mtl->tex_diffuse = terrain->Texture();

    materials.append(mtl);

    List<TerrainLayer>& layers = terrain->GetLayers();
    for (i = 0; i < layers.size(); i++) {
        Bitmap* tex0 = layers.at(i)->GetTileTexture();
        Bitmap* tex1 = 0;
        Bitmap* texd = layers.at(i)->GetDetailTexture();

        if (i < layers.size()-1)
        tex1 = layers.at(i+1)->GetTileTexture();

        if (!texd)
        texd = terrain->DetailTexture(0);

        mtl = new Material;
        mtl->Ka = ColorValue(0.5f, 0.5f, 0.5f);
        mtl->Kd = ColorValue(0.3f, 0.6f, 0.2f);
        mtl->Ks = Color::Black;

        if ((i & 1) != 0) {
            mtl->tex_diffuse     = tex1;
            mtl->tex_alternate   = tex0;
        }
        else {
            mtl->tex_diffuse     = tex0;
            mtl->tex_alternate   = tex1;
        }

        mtl->tex_detail         = texd;

        materials.append(mtl);
    }

    for (i = 0; i <= max_detail; i++)
    BuildDetailLevel(i);

    model = detail_levels[1];
}

// +--------------------------------------------------------------------+

TerrainPatch::TerrainPatch(Terrain*       terr,
const Rect&    r,
const Point&   p1,
const Point&   p2,
double         sea_level)
: ndetail(0), terrain(terr), rect(r), water(0)
{
    luminous   = true;   // water is lit by the graphics engine
    own_model  = false;  // manage the model lifetimes in this derived class

    max_detail = Terrain::DetailLevel();
    scale      = fabs(p1.x - p2.x) / (PATCH_SIZE-1);
    mtnscale   = 0;
    base       = sea_level;
    size       = p2.x - p1.x;

    ZeroMemory(detail_levels, sizeof(detail_levels));

    terrain_width = 0;

    loc   = (p1 + p2) * 0.5;
    loc.y = base;

    radius    = (float) (size * 0.75);
    heights   = new float[MAX_VERTS];

    float* pHeight = heights;
    int    i, j;

    for (i = 0; i < PATCH_SIZE; i++) {
        for (j = 0; j < PATCH_SIZE; j++) {
            *pHeight++ = (float) sea_level;
        }
    }

    Material* mtl = new Material;
    mtl->Ka = Color::Gray;
    mtl->Kd = Color::White;
    mtl->Ks = Color::White;
    mtl->power       = 30.0f;
    mtl->shadow      = false;
    mtl->tex_diffuse = terrain->WaterTexture();
    //strcpy_s(mtl->shader, "WaterReflections");
    materials.append(mtl);

    water = terrain->GetWater(1);

    for (i = 0; i <= max_detail; i++)
    BuildDetailLevel(i);

    model = detail_levels[1];
}

// +--------------------------------------------------------------------+

TerrainPatch::~TerrainPatch()
{
    delete [] heights;

    for (int i = 0; i < MAX_LOD; i++) {
        Model* m = detail_levels[i];

        if (m) {
            m->GetMaterials().clear();
            delete m;
        }
    }

    materials.destroy();
}

// +--------------------------------------------------------------------+

void
TerrainPatch::SetScales(double s, double m, double b)
{
    scale    = s;
    mtnscale = m;
    base     = b;
}

// +--------------------------------------------------------------------+

static int mcomp(const void* a, const void* b)
{
    Poly* pa = (Poly*) a;
    Poly* pb = (Poly*) b;

    if (pa->sortval == pb->sortval)
    return 0;

    if (pa->sortval < pb->sortval)
    return 1;

    return -1;
}


static void bisect(VertexSet* vset, int v[4])
{
    double d1 = fabs(vset->loc[ v[0] ].y -
    vset->loc[ v[3] ].y);

    double d2 = fabs(vset->loc[ v[1] ].y -
    vset->loc[ v[2] ].y);

    if (d2 < 0.7*d1) {
        int odd[4] = { v[1], v[3], v[0], v[2] };
        for (int i = 0; i < 4; i++)
        v[i] = odd[i];
    }
}

bool
TerrainPatch::BuildDetailLevel(int level)
{
    int i, j;

    int detail_size = 1 << level;
    int ds1 = detail_size+1;

    if (detail_size > PATCH_SIZE)
    return false;

    Model* model   = new Model;
    detail_levels[level] = model;

    model->SetLuminous(luminous);
    model->SetDynamic(true);

    const int   NUM_STRIPS        = 4;
    const int   NUM_INDICES_TRI   = 3;
    const int   NUM_INDICES_QUAD  = 6;

    int nverts     = ds1*ds1 + ds1*2*NUM_STRIPS;
    int npolys     = detail_size*detail_size*2;
    int strip_len  = detail_size;
    int total      = npolys + strip_len*NUM_STRIPS;

    if (water) {
        nverts      = ds1*ds1;
        strip_len   = 0;
        total       = npolys;
    }

    Surface*    s     = new Surface;
    VertexSet*  vset  = 0;

    if (s) {
        s->SetName("default");
        s->CreateVerts(nverts);
        s->CreatePolys(total);
        s->AddIndices(npolys*NUM_INDICES_TRI + strip_len*NUM_STRIPS*NUM_INDICES_QUAD);

        vset = s->GetVertexSet();
        if (!water)
        vset->CreateAdditionalTexCoords();

        ZeroMemory(vset->loc,      nverts * sizeof(Vec3));
        ZeroMemory(vset->diffuse,  nverts * sizeof(DWORD));
        ZeroMemory(vset->specular, nverts * sizeof(DWORD));
        ZeroMemory(vset->tu,       nverts * sizeof(float));
        ZeroMemory(vset->tv,       nverts * sizeof(float));
        if (!water) {
            ZeroMemory(vset->tu1,      nverts * sizeof(float));
            ZeroMemory(vset->tv1,      nverts * sizeof(float));
        }
        ZeroMemory(vset->rw,       nverts * sizeof(float));

        // initialize vertices
        Vec3*  pVert   = vset->loc;
        float* pTu     = vset->tu;
        float* pTv     = vset->tv;
        float* pTu1    = vset->tu1;
        float* pTv1    = vset->tv1;
        DWORD* pSpec   = vset->specular;

        int    dscale  = (PATCH_SIZE-1)/detail_size;
        double dt      = 0.0625 / (ds1-1); // terrain texture scale
        double dtt     = 2.0000 / (ds1-1); // tile texture scale
        double tu0     = (double) rect.x / rect.w / 16.0 + 1.0/16.0;
        double tv0     = (double) rect.y / rect.h / 16.0;

        // surface verts
        for (i = 0; i < ds1; i++) {
            for (j = 0; j < ds1; j++) {
                *pVert   = Vec3((float) (j* scale * dscale - (HALF_PATCH_SIZE*scale)),
                (float) (heights[i*dscale*PATCH_SIZE + j*dscale]),
                (float) (i* scale * dscale - (HALF_PATCH_SIZE*scale)));

                if (level >= 2) {
                    *pTu++   = (float) (-j*dtt);
                    *pTv++   = (float) ( i*dtt);

                    if (level >= 4 && !water) {
                        *pTu1++  = (float) (-j*dtt*3);
                        *pTv1++  = (float) ( i*dtt*3);
                    }

                    *pSpec++ = BlendValue(pVert->y);
                }

                else {
                    *pTu++   = (float) (tu0 - j*dt);
                    *pTv++   = (float) (tv0 + i*dt);
                }

                pVert++;
            }
        }

        if (!water) {
            // strip 1 & 2 verts
            for (i = 0; i < ds1; i += detail_size) {
                for (j = 0; j < ds1; j++) {
                    Vec3 vl  = Vec3((float) (j* scale * dscale - (HALF_PATCH_SIZE*scale)),
                    (float) (heights[i*dscale*PATCH_SIZE + j*dscale]),
                    (float) (i* scale * dscale - (HALF_PATCH_SIZE*scale)));

                    *pVert++ = vl;

                    DWORD blend = 0;

                    if (level >= 2) {
                        blend = BlendValue(vl.y);

                        *pSpec++ = blend;
                        *pTu++   = (float) (-j*dtt);
                        *pTv++   = (float) ( i*dtt);
                    }

                    else {
                        *pTu++   = (float) (tu0 - j*dt);
                        *pTv++   = (float) (tv0 + i*dt);
                    }

                    vl.y     = -5000.0f;

                    *pVert++ = vl;

                    if (level >= 2) {
                        *pSpec++ = blend;
                        *pTu++   = (float) (-j*dtt);
                        *pTv++   = (float) ( i*dtt);
                    }

                    else {
                        *pTu++   = (float) (tu0 - j*dt);
                        *pTv++   = (float) (tv0 + i*dt);
                    }
                }
            }

            // strip 3 & 4 verts
            for (j = 0; j < ds1; j += detail_size) {
                for (i = 0; i < ds1; i++) {
                    Vec3 vl  = Vec3((float) (j* scale * dscale - (HALF_PATCH_SIZE*scale)),
                    (float) (heights[i*dscale*PATCH_SIZE + j*dscale]),
                    (float) (i* scale * dscale - (HALF_PATCH_SIZE*scale)));

                    *pVert++ = vl;

                    DWORD blend = 0;

                    if (level >= 2) {
                        blend = BlendValue(vl.y);

                        *pSpec++ = blend;
                        *pTu++   = (float) (-j*dtt);
                        *pTv++   = (float) ( i*dtt);
                    }

                    else {
                        *pTu++   = (float) (tu0 - j*dt);
                        *pTv++   = (float) (tv0 + i*dt);
                    }

                    vl.y     = -5000.0f;

                    *pVert++ = vl;

                    if (level >= 2) {
                        *pSpec++ = blend;
                        *pTu++   = (float) (-j*dtt);
                        *pTv++   = (float) ( i*dtt);
                    }

                    else {
                        *pTu++   = (float) (tu0 - j*dt);
                        *pTv++   = (float) (tv0 + i*dt);
                    }
                }
            }
        }

        Material* m = materials.first();

        // initialize the polys
        for (i = 0; i < npolys; i++) {
            Poly* p        = s->GetPolys() + i;
            p->nverts      = 3;
            p->vertex_set  = vset;
            p->visible     = 1;
            p->sortval     = 0;
            p->material    = m;

            if (level >= 2 && !water) {
                p->material = materials.at(1);
                p->sortval  = 1;
            }
        }

        for (i = npolys; i < total; i++) {
            Poly* p        = s->GetPolys() + i;
            p->nverts      = 4;
            p->vertex_set  = vset;
            p->visible     = 1;
            p->sortval     = 0;
            p->material    = m;
        }

        int index = 0;

        // build main patch polys:
        for (i = 0; i < detail_size; i++) {
            for (j = 0; j < detail_size; j++) {
                int v[4] = {
                    (ds1 * (i  ) + (j  )),
                    (ds1 * (i  ) + (j+1)),
                    (ds1 * (i+1) + (j  )),
                    (ds1 * (i+1) + (j+1)) };

                bisect(vset, v);

                // first triangle
                Poly* p = s->GetPolys() + index++;
                p->verts[0]   = v[0];
                p->verts[1]   = v[1];
                p->verts[2]   = v[3];

                if (level >= 2 && !water) {
                    int layer = CalcLayer(p) + 1;
                    p->material = materials.at(layer);
                    p->sortval  = layer;
                }

                // second triangle
                p = s->GetPolys() + index++;
                p->verts[0]   = v[0];
                p->verts[1]   = v[3];
                p->verts[2]   = v[2];

                if (level >= 2 && !water) {
                    int layer = CalcLayer(p) + 1;
                    p->material = materials.at(layer);
                    p->sortval  = layer;
                }
            }
        }

        // build vertical edge strip polys:

        if (!water) {
            for (i = 0; i < NUM_STRIPS; i++) {
                Poly* p = s->GetPolys() + npolys + i*strip_len;
                int   base_index = ds1*ds1 + ds1*2*i;

                for (j = 0; j < strip_len; j++) {
                    int v       = base_index + j * 2;
                    p->nverts   = 4;

                    if (i == 1 || i == 2) {
                        p->verts[0] = v;
                        p->verts[1] = v+2;
                        p->verts[2] = v+3;
                        p->verts[3] = v+1;
                    }

                    else {
                        p->verts[0] = v;
                        p->verts[1] = v+1;
                        p->verts[2] = v+3;
                        p->verts[3] = v+2;
                    }

                    if (level >= 2) {
                        int layer = CalcLayer(p) + 1;
                        p->material = materials.at(layer);
                        p->sortval  = layer;
                    }

                    p++;
                }
            }
        }

        // update the poly planes:
        for (i = 0; i < total; i++) {
            Poly*   p      = s->GetPolys() + i;
            Plane&  plane  = p->plane;
            WORD*   v      = p->verts;

            plane = Plane(vset->loc[v[0]] + loc,
            vset->loc[v[1]] + loc,
            vset->loc[v[2]] + loc);
        }

        s->Normalize();

        // create continguous segments for each material:
        // sort the polys by material index:
        qsort((void*) s->GetPolys(), s->NumPolys(), sizeof(Poly), mcomp);

        // then assign them to cohesive segments:
        Segment* segment = 0;
        Poly*    spolys  = s->GetPolys();

        for (int n = 0; n < s->NumPolys(); n++) {
            if (segment && segment->material == spolys[n].material) {
                segment->npolys++;
            }
            else {
                segment = 0;
            }

            if (!segment) {
                segment = new Segment;

                segment->npolys   = 1;
                segment->polys    = &spolys[n];
                segment->material = segment->polys->material;
                segment->model    = model;

                s->GetSegments().append(segment);
            }
        }

        Solid::EnableCollision(false);
        model->AddSurface(s);
        Solid::EnableCollision(true);

        // copy vertex normals:
        const Vec3B* tnorms = terrain->Normals();

        for (i = 0; i < ds1; i++) {
            for (j = 0; j < ds1; j++) {

                if (water) {
                    vset->nrm[i*ds1+j] = Point(0,1,0);
                }

                // blend adjacent normals:
                else if (dscale > 1) {
                    Point normal;

                    // but don't blend more than 16 normals per vertex:
                    int step = 1;
                    if (dscale > 4)
                    step = dscale / 4;

                    for (int dy = -dscale/2; dy < dscale/2; dy += step) {
                        for (int dx = -dscale/2; dx < dscale/2; dx += step) {
                            int ix = rect.x + (ds1-1-j)*dscale + dx;
                            int iy = rect.y + i*dscale + dy;

                            if (ix < 0)                ix = 0;
                            if (ix > terrain_width-1)  ix = terrain_width-1;
                            if (iy < 0)                iy = 0;
                            if (iy > terrain_width-1)  iy = terrain_width-1;

                            Vec3B vbn = tnorms[iy*terrain_width + ix];
                            normal += Point((128-vbn.x)/127.0, (vbn.z-128)/127.0, (vbn.y-128)/127.0);
                        }
                    }

                    normal.Normalize();
                    vset->nrm[i*ds1+j] = normal;
                }

                // just copy the one normal:
                else {
                    Vec3B vbn    = tnorms[(rect.y + i*dscale)*terrain_width + (rect.x + (ds1-1-j) * dscale)];
                    Point normal = Point((128-vbn.x)/127.0, (vbn.z-128)/127.0, (vbn.y-128)/127.0);
                    vset->nrm[i*ds1+j] = normal;
                }
            }
        }

        if (!water) {
            pVert = &vset->nrm[ds1*ds1];

            // strip 1 & 2 verts
            for (i = 0; i < ds1; i += detail_size) {
                for (j = 0; j < ds1; j++) {
                    Vec3 vn  = vset->nrm[i*ds1 + j];

                    *pVert++ = vn;
                    *pVert++ = vn;
                }
            }

            // strip 3 & 4 verts
            for (j = 0; j < ds1; j += detail_size) {
                for (i = 0; i < ds1; i++) {
                    Vec3 vn  = vset->nrm[i*ds1 + j];

                    *pVert++ = vn;
                    *pVert++ = vn;
                }
            }
        }
    }

    if (level > max_detail)
    max_detail = level;

    return true;
}

// +--------------------------------------------------------------------+

DWORD
TerrainPatch::BlendValue(double y)
{
    if (terrain && y >= 0 && !water) {
        // find the proper layer:
        for (int i = 0; i < terrain->GetLayers().size(); i++) {
            TerrainLayer* layer = terrain->GetLayers().at(i);

            if (y >= layer->GetMinHeight() && y < layer->GetMaxHeight()) {
                double scale = (y-layer->GetMinHeight()) / (layer->GetMaxHeight()-layer->GetMinHeight());

                if (scale < 0.2)
                scale = 0;
                else if (scale > 0.8)
                scale = 1;
                else
                scale = (scale - 0.2) / 0.6;

                if ((i & 1) == 0) {
                    scale = 1 - scale;
                }

                DWORD val = (DWORD) (scale*255);

                return val << 24;
            }
        }
    }

    return 0;
}

int
TerrainPatch::CalcLayer(Poly* poly)
{
    if (terrain && poly) {
        if (water)
        return 0;

        double y = 1e6;

        for (int i = 0; i < poly->nverts; i++) {
            double h = poly->vertex_set->loc[ poly->verts[i] ].y;

            if (h >= 0 && h < y) {
                y = h;
            }
        }

        if (y <= terrain->GetLayers().first()->GetMinHeight())
        return 0;

        for (int i = 0; i < terrain->GetLayers().size(); i++) {
            TerrainLayer* layer = terrain->GetLayers().at(i);

            if (y >= layer->GetMinHeight() && y < layer->GetMaxHeight()) {
                return i;
            }
        }
    }

    return -1;
}

// +--------------------------------------------------------------------+

void
TerrainPatch::UpdateSurfaceWaves(Vec3& eyePos)
{
    if (water && model && model->NumVerts() > 1) {
        Surface* s = model->GetSurfaces().first();
        if (s) {
            VertexSet* vset = s->GetVertexSet();
            for (int i = 0; i < vset->nverts; i++)
            vset->loc[i].y = 0.0f;

            water->UpdateSurface(eyePos, vset);
        }
    }
}

// +--------------------------------------------------------------------+

int
TerrainPatch::CollidesWith(Graphic& o)
{
    return 0;
}

// +--------------------------------------------------------------------+

void
TerrainPatch::SelectDetail(Projector* projector)
{
    // This is where all the work is done,
    // Delegate to the overall terrain to
    // compute a detail level for every patch:

    if (terrain) {
        terrain->SelectDetail(projector);
    }

    // Build detail levels on demand:

    if (detail_levels[ndetail] == 0)
    BuildDetailLevel(ndetail);
}

void
TerrainPatch::SetDetailLevel(int nd)
{
    if (nd >= 0 && nd <= max_detail) {
        if (ndetail != nd)
        DeletePrivateData();

        ndetail = nd;

        // build detail levels on demand:
        if (detail_levels[ndetail] == 0)
        BuildDetailLevel(ndetail);

        model = detail_levels[ndetail];

        if (water)
        water = terrain->GetWater(ndetail);
    }
}

// +--------------------------------------------------------------------+

void
TerrainPatch::Illuminate(Color ambient, List<Light>& lights)
{
    if (!model || model->NumVerts() < 1) return;
    Surface* s = model->GetSurfaces().first();
    if (!s) return;

    illuminating = true;

    // clear the solid lights to ambient:
    VertexSet*  vset   = s->GetVertexSet();
    int         nverts = vset->nverts;
    DWORD       aval   = ambient.Value();

    for (int i = 0; i < nverts; i++) {
        vset->diffuse[i]  = aval;
    }

    TerrainRegion* trgn     = terrain->GetRegion();
    bool           eclipsed = false;
    bool           first    = terrain->IsFirstPatch(this);

    if (trgn && !first) {
        eclipsed = trgn->IsEclipsed();
    }

    // for sun and back lights:
    ListIter<Light> iter = lights;
    while (++iter) {
        Light* light = iter.value();

        if (!light->IsDirectional())                                // only do sun and
        continue;                                                // back lights

        if (light->CastsShadow() && first) {
            eclipsed  = light->Location().y < -100 ||                // has sun set, or

            scene->IsLightObscured(vset->loc[0],         // is sun in eclipse
            light->Location(),    // by orbital body
            radius);              // such as a moon?
        }

        if (!light->CastsShadow() || !eclipsed) {
            Vec3 vl = light->Location();
            vl.Normalize();

            for (int i = 0; i < nverts; i++) {
                Vec3&  nrm = vset->nrm[i];
                double val = 0;
                double gain = vl * nrm;

                if (gain > 0) {
                    val = light->Intensity() * (0.85 * gain);

                    if (val > 1)
                    val = 1;
                }

                if (val > 0.01)
                vset->diffuse[i] = ((light->GetColor().dim(val)) + vset->diffuse[i]).Value();
            }
        }
    }

    // combine blend weights:
    if (ndetail >= 2) {
        for (int i = 0; i < nverts; i++) {
            vset->diffuse[i] = vset->specular[i] | (vset->diffuse[i] & 0x00ffffff);
        }
    }

    if (trgn && first) {
        trgn->SetEclipsed(eclipsed);
    }

    InvalidateSurfaceData();
    illuminating = false;
}

// +--------------------------------------------------------------------+

void
TerrainPatch::Render(Video* video, DWORD flags)
{
    if (max_height < 0)
    return;

    if (flags & RENDER_ADDITIVE)
    return;

    if (!model)
    model = detail_levels[0];

    if (scene) {
        /***
    *** TWO PASS LIGHTING FOR TERRAIN SHADOWS DOESN'T
    *** WORK - IT MESSES UP THE HARDWARE FOG CALCS
    ***
    *** PLUS, IT'S INCREDIBLY SLOW!!!
    ***/

        if ((flags & RENDER_ADD_LIGHT) != 0)
        return;

        if (water) {
            Vec3 vec(0, 0, 0);
            UpdateSurfaceWaves(vec);
            Illuminate(scene->Ambient(), scene->Lights());
        }
        else {
            Illuminate(scene->Ambient(), scene->Lights());
        }
    }
    else {
        if ((flags & RENDER_ADD_LIGHT) != 0)
        return;
    }

    Bitmap* details[16];
    ZeroMemory(details, sizeof(details));

    if (ndetail < 3) {
        for (int i = 0; i < 16 && i < materials.size(); i++) {
            Material* mtl = materials[i];

            if (mtl->tex_detail) {
                details[i] = mtl->tex_detail;
                mtl->tex_detail = 0;
            }
        }
    }

    double   visibility  = terrain->GetRegion()->GetWeather().Visibility();
    FLOAT    fog_density = (FLOAT) (terrain->GetRegion()->FogDensity() * 2.5e-5 * 1/visibility);

    video->SetRenderState(Video::LIGHTING_ENABLE,   false);
    video->SetRenderState(Video::SPECULAR_ENABLE,   false); //water != 0);
    video->SetRenderState(Video::FOG_ENABLE,        true);
    video->SetRenderState(Video::FOG_COLOR,         terrain->GetRegion()->FogColor().Value());
    video->SetRenderState(Video::FOG_DENSITY,       *((DWORD*) &fog_density));

    // Too bad this doesn't work right.  But it makes the
    // ground mostly disappear. :-(
    //
    //video->SetRenderState(Video::Z_BIAS,            -2);

    Solid::Render(video, flags);

    video->SetRenderState(Video::LIGHTING_ENABLE,   true);
    video->SetRenderState(Video::SPECULAR_ENABLE,   true);
    video->SetRenderState(Video::FOG_ENABLE,        false);
    //video->SetRenderState(Video::Z_BIAS,            0);

    if (ndetail < 3) {
        for (int i = 0; i < 16 && i < materials.size(); i++) {
            Material* mtl = materials[i];

            if (details[i] && !mtl->tex_detail) {
                mtl->tex_detail = details[i];
            }
        }
    }
}

// +--------------------------------------------------------------------+

int
TerrainPatch::CheckRayIntersection(Point obj_pos, Point dir, double len, Point& ipt, bool ttpas)
{
    Point  light_pos = obj_pos + dir * len;
    int    impact    = light_pos.y < -100;

    // Special case for illumination -
    // just check if sun is above or below the horizon:

    if (illuminating || impact) {
        return impact;
    }

    if (obj_pos.x != 0 || obj_pos.y != 0 || obj_pos.z != 0) {
        return impact;
    }

    // the rest of this code is only used for eclipsing
    // the solar lens flare:

    // check right angle spherical distance:
    Point  d0 = loc;
    Point  d1 = d0.cross(dir);
    double dlen = d1.length();          // distance of point from line

    if (dlen > radius)                  // clean miss
    return 0;                        // (no impact)

    // make sure some part of this patch falls between
    // the camera and the sun:

    Point closest = loc + dir * radius;

    if (closest * dir < 0)
    return 0;

    // probable hit at this point...
    // test for polygon intersection:
    if (!model)
    return 0;

    Surface* s = model->GetSurfaces().first();

    if (!s)
    return 0;


    // transform ray into object space:
    Matrix xform(Orientation());

    Vec3 tmp = dir;

    dir.x = tmp * Vec3(xform(0,0), xform(0,1), xform(0,2));
    dir.y = tmp * Vec3(xform(1,0), xform(1,1), xform(1,2));
    dir.z = tmp * Vec3(xform(2,0), xform(2,1), xform(2,2));

    tmp = obj_pos-loc;

    obj_pos.x = tmp * Vec3(xform(0,0), xform(0,1), xform(0,2));
    obj_pos.y = tmp * Vec3(xform(1,0), xform(1,1), xform(1,2));
    obj_pos.z = tmp * Vec3(xform(2,0), xform(2,1), xform(2,2));

    double min = 2 * len;

    // check each polygon:
    Poly*    p = s->GetPolys();

    for (int i = 0; i < s->NumPolys(); i++) {
        Point  v = p->plane.normal;
        double d = p->plane.distance;

        double denom = dir*v;

        if (denom < -1.0e-5) {
            Point  P    = v * d;
            double ilen = ((P-obj_pos)*v)/denom;

            if (ilen > 0 && ilen < min) {
                Point intersect = obj_pos + dir * ilen;

                if (p->Contains(intersect)) {
                    ipt = intersect;
                    min = ilen;
                    impact = 1;
                }
            }
        }

        p++;
    }

    // xform impact point back into world coordinates:

    if (impact) {
        ipt = (ipt * Orientation()) + loc;
    }

    return impact;
}

// +--------------------------------------------------------------------+

double
TerrainPatch::Height(double x, double z) const
{
    if (water) return base;

    double   height = 0;

    x /= scale;
    z /= scale;

    int x0 = (int) x;
    int z0 = (int) z;

    if (x0 >= 0 && x0 < PATCH_SIZE && z0 >= 0 && z0 < PATCH_SIZE) {
        double dx = x-x0;
        double dz = z-z0;

        double h[4];

        h[0] = heights[(z0*PATCH_SIZE     + x0)];
        h[1] = heights[((z0+1)*PATCH_SIZE + x0)];
        h[2] = heights[(z0*PATCH_SIZE     + x0+1)];
        h[3] = heights[((z0+1)*PATCH_SIZE + x0+1)];

        // if level, just return height of one vertex:
        if (h[0] == h[1] && h[1] == h[2] && h[2] == h[3]) {
            height = h[0];
        }

        // if sloped, interpolate between vertex heights:
        else {
            double hl = h[0]*(1-dz) + h[1]*dz;
            double hr = h[2]*(1-dz) + h[3]*dz;

            height = hl*(1-dx) + hr*dx + 5; // fudge
        }
    }

    if (height < 0)
    height = 0;

    return height;
}