/* render.c: rendering ELEMENTs */
/* TODO: mesh balancing */

#include "mcradP.h"
#include "hierarchy.h"
#include "camera.h"
#include "render.h"

static RGB RatioToColor(float ratio)
{
  RGB color;

  if (ratio < 0.) {
    RGBSET(color, 0., 0., 1.);
  } else if (ratio < 1.) {
    RGBSET(color, 0., 1.-ratio, 0.);
  } else if (ratio < 2.) {
    RGBSET(color, ratio - 1., 0., 0.);
  } else {
    RGBSET(color, 1., 0., 0.);
  }
  return color;
}

RGB ElementColor(ELEMENT *element)
{
  RGB color;

  switch (mcr.show) {
  case SHOW_TOTAL_RADIANCE:
  case SHOW_INDIRECT_RADIANCE:
    RadianceToRGB(ElementDisplayRadiance(element), &color);
    break;
  case SHOW_IMPORTANCE:
  {
#ifdef IDMCR
    float gray = element->imp>1. ? 1. : element->imp<0. ? 0. : element->imp;
    RGBSET(color, gray, gray, gray);
    break;
#endif
  }
  default:
    Fatal(-1, "ElementColor", "Don't know what to display (mcr.show = %d)", mcr.show);
  }

  return color;
}

static COLOR VertexRadiance(VERTEX *v)
{
  int count = 0;
  COLOR radiance;

  COLORCLEAR(radiance);
  ForAllElements(elem, v->radiance_data) {
    if (!elem->regular_subelements) {
      COLOR elemrad = ElementDisplayRadiance(elem);
      COLORADD(radiance, elemrad, radiance);
      count++;
    }
  } EndForAll;

  if (count>0)
    COLORSCALEINVERSE((float)count, radiance, radiance);

  return radiance;
}

/* same as above but for the reflectance
 * (important in case of texturing) */
COLOR VertexReflectance(VERTEX *v)
{
  int count = 0;
  COLOR rd;

  COLORCLEAR(rd);
  ForAllElementsSharingVertex(elem, v) {
    if (!elem->regular_subelements) {
      COLORADD(rd, elem->Rd, rd);
      count++;
    }
  } EndForAll;

  if (count>0)
    COLORSCALEINVERSE((float)count, rd, rd);

  return rd;
}

/* same as above but for importance */
static float VertexImportance(VERTEX *v)
{
  int count = 0;
  float imp = 0.;
#ifdef IDMCR
  ForAllElements(elem, v->radiance_data) {
    if (!elem->regular_subelements) {
      imp += elem->imp;
      count++;
    }
  } EndForAll;

  if (count>0)
    imp /= (float)count;
#endif

  return imp;
}

RGB VertexColor(VERTEX *v)
{
  switch (mcr.show) {
  case SHOW_TOTAL_RADIANCE:
  case SHOW_INDIRECT_RADIANCE:
    RadianceToRGB(VertexRadiance(v), &v->color);
    break;
  case SHOW_IMPORTANCE:
  {
    float gray = VertexImportance(v);
    if (gray > 1.) gray = 1.;
    if (gray < 0.) gray = 0.;
    RGBSET(v->color, gray, gray, gray);
    break;
  }
  default:
    Fatal(-1, "VertexColor", "Don't know what to display (mcr.show = %d)", mcr.show);
  }

  return v->color;
}

/* compute new vertex colors */
void ElementComputeNewVertexColors(ELEMENT *elem)
{
  VertexColor(elem->vertex[0]);
  VertexColor(elem->vertex[1]);
  VertexColor(elem->vertex[2]);
  if (elem->nrvertices > 3)
  VertexColor(elem->vertex[3]);
}

void ElementAdjustTVertexColors(ELEMENT *elem)
{
  VERTEX *m[4];
  int i, n;
  for (i=0, n=0; i<elem->nrvertices; i++) {
    m[i] = EdgeMidpointVertex(elem, i);
    if (m[i]) n++;
  }

  if (n > 0) {
    RGB color = ElementColor(elem);
    for (i=0; i<elem->nrvertices; i++) {
      if (m[i]) {
	m[i]->color.r = (m[i]->color.r + color.r) * 0.5;
	m[i]->color.g = (m[i]->color.g + color.g) * 0.5;
	m[i]->color.b = (m[i]->color.b + color.b) * 0.5;
      }
    }
  }
}

static void RenderTriangle(VERTEX *v1, VERTEX *v2, VERTEX *v3)
{
  RGB col[3];
  VECTOR vert[3];

  vert[0] = *(v1->point); col[0] = v1->color;
  vert[1] = *(v2->point); col[1] = v2->color;
  vert[2] = *(v3->point); col[2] = v3->color;
  RenderPolygonGouraud(3, vert, col);

  if (renderopts.draw_outlines) {
    int i;
    for (i=0; i<3; i++) {
      VECTOR d;
      VECTORSUBTRACT(Camera.eyep, vert[i], d);
      VECTORADDSCALED(vert[i], 0.01, d, vert[i]);
    }

    RenderSetColor(&renderopts.outline_color);
    RenderLine(&vert[0], &vert[1]);
    RenderLine(&vert[1], &vert[2]);
    RenderLine(&vert[2], &vert[0]);
  }
}

static void RenderQuadrilateral(VERTEX *v1, VERTEX *v2, VERTEX *v3, VERTEX *v4)
{
  RGB col[4];
  VECTOR vert[4];

  vert[0] = *(v1->point); col[0] = v1->color;
  vert[1] = *(v2->point); col[1] = v2->color;
  vert[2] = *(v3->point); col[2] = v3->color;
  vert[3] = *(v4->point); col[3] = v4->color;
  RenderPolygonGouraud(4, vert, col);

  if (renderopts.draw_outlines) {
    int i;
    for (i=0; i<4; i++) {
      VECTOR d;
      VECTORSUBTRACT(Camera.eyep, vert[i], d);
      VECTORADDSCALED(vert[i], 0.01, d, vert[i]);
    }

    RenderSetColor(&renderopts.outline_color);
    RenderLine(&vert[0], &vert[1]);
    RenderLine(&vert[1], &vert[2]);
    RenderLine(&vert[2], &vert[3]);
    RenderLine(&vert[3], &vert[0]);
  }
}

/* TODO: The T-vertex elimination code only fully eliminates T-vertices in
 * balanced meshes. Meshes are not yet balanced [PhB - 9901]. */

static void TriangleTVertexElimination(VERTEX **v, VERTEX **m, int nrTvertices, 
					  void (*do_triangle)(VERTEX *, VERTEX *, VERTEX *),
					  void (*do_quadrilateral)(VERTEX *, VERTEX *, VERTEX *, VERTEX *))
{
  int a, b, c;

  switch (nrTvertices) {
  case 0:
    do_triangle(v[0], v[1], v[2]);
    break;
  case 1:
    for (a=0; a<3; a++) if (m[a]) break;
    b = (a+1)%3; c = (a+2)%3;
    do_triangle(m[a], v[c], v[a]);
    do_triangle(m[a], v[b], v[c]);
    break;
  case 2:
    for (a=0; a<3; a++) if (!m[a]) break;
    b = (a+1)%3; c = (a+2)%3;
    do_triangle(m[b], v[a], v[b]);
    do_triangle(m[b], m[c], v[a]);
    do_triangle(m[b], v[c], m[c]);
    break;
  case 3:
    do_triangle(v[0], m[0], m[2]);
    do_triangle(v[1], m[1], m[0]);
    do_triangle(v[2], m[2], m[1]);
    do_triangle(m[0], m[1], m[2]);
    break;
  }
}

static void QuadrilateralTVertexElimination(VERTEX **v, VERTEX **m, int nrTvertices,
					       void (*do_triangle)(VERTEX *, VERTEX *, VERTEX *),
					       void (*do_quadrilateral)(VERTEX *, VERTEX *, VERTEX *, VERTEX *))
{
  int a, b, c, d;

  switch (nrTvertices) {
  case 0:
    do_quadrilateral(v[0], v[1], v[2], v[3]);
    break;
  case 1:
    for (a=0; a<4; a++) if (m[a]) break;
    b = (a+1)%4; c = (a+2)%4; d = (a+3)%4;
    do_triangle(m[a], v[d], v[a]);
    do_triangle(m[a], v[c], v[d]);
    do_triangle(m[a], v[b], v[c]);
    break;
  case 2:
    for (a=0; a<4; a++) if (m[a]) break;
    b = (a+1)%4; c = (a+2)%4; d = (a+3)%4;
    if (m[d]) {a = d; b = (a+1)%4; c = (a+2)%4; d = (a+3)%4;}
    if (m[b]) {
      do_triangle(m[a], v[b], m[b]);
      do_triangle(m[b], v[c], v[d]);
      do_triangle(v[d], m[a], m[b]);
      do_triangle(v[d], v[a], m[a]);
    } else {
      do_quadrilateral(v[a], m[a], m[c], v[d]);
      do_quadrilateral(m[a], v[b], v[c], m[c]);
    }
    break;
  case 3:
    for (a=0; a<4; a++) if (!m[a]) break;
    b = (a+1)%4; c = (a+2)%4; d = (a+3)%4;
    do_quadrilateral(v[a], v[b], m[b], m[d]);
    do_triangle(m[b], v[c], m[c]);
    do_triangle(m[c], v[d], m[d]);
    do_triangle(m[b], m[c], m[d]);
    break;
  case 4:
    do_triangle(v[0], m[0], m[3]);
    do_triangle(v[1], m[1], m[0]);
    do_triangle(v[2], m[2], m[1]);
    do_triangle(v[3], m[3], m[2]);
    do_quadrilateral(m[0], m[1], m[2], m[3]);
    break;
  }
}

static void RenderTriangularElement(VERTEX **v, VERTEX **m, int nrTvertices)
{
  TriangleTVertexElimination(v, m, nrTvertices, RenderTriangle, RenderQuadrilateral);
}

static void RenderQuadrilateralElement(VERTEX **v, VERTEX **m, int nrTvertices)
{
  QuadrilateralTVertexElimination(v, m, nrTvertices, RenderTriangle, RenderQuadrilateral);
}

void ElementTVertexElimination(ELEMENT *elem,
			       void (*do_triangle)(VERTEX *, VERTEX *, VERTEX *),
			       void (*do_quadrilateral)(VERTEX *, VERTEX *, VERTEX *, VERTEX *))
{
  VERTEX *m[4];
  int i, n;
  for (i=0, n=0; i<elem->nrvertices; i++) {
    m[i] = EdgeMidpointVertex(elem, i);
    if (m[i]) n++;
  }
  
  if (elem->nrvertices == 3)
    TriangleTVertexElimination(elem->vertex, m, n, do_triangle, do_quadrilateral);
  else
    QuadrilateralTVertexElimination(elem->vertex, m, n, do_triangle, do_quadrilateral);
}

void RenderElementOutline(ELEMENT *elem)
{
  VECTOR verts[4];
  int i;

  /* test whether eye point is in front of the patch */
  if (VECTORDOTPRODUCT(elem->pog.patch->normal, Camera.eyep) + elem->pog.patch->plane_constant < 0.)
    return;

  for (i=0; i<elem->nrvertices; i++) {
    VECTOR d;
    verts[i] = *(elem->vertex[i]->point);
    VECTORSUBTRACT(Camera.eyep, verts[i], d);
    VECTORADDSCALED(verts[i], 0.0001, d, verts[i]);
  }

  RenderSetColor(&renderopts.outline_color);
  RenderLine(&verts[0], &verts[1]);
  RenderLine(&verts[1], &verts[2]);
  if (elem->nrvertices == 3) 
    RenderLine(&verts[2], &verts[0]);
  else {
    RenderLine(&verts[2], &verts[3]);
    RenderLine(&verts[3], &verts[0]);
  }
}

void RenderElement(ELEMENT *elem)
{
  VECTOR verts[4];

#ifdef DO_BACKFACE_CULLING_YOURSELF
  if (renderopts.backface_culling) {
    /* test whether eye point is in front of the patch */
    if (VECTORDOTPRODUCT(elem->pog.patch->normal, Camera.eyep) + elem->pog.patch->plane_constant < 0.)
      return;
  }
#endif

  if (renderopts.smooth_shading && hierarchy.tvertex_elimination) {
    VERTEX *m[4];
    int i, n;
    for (i=0, n=0; i<elem->nrvertices; i++) {
      m[i] = EdgeMidpointVertex(elem, i);
      if (m[i]) n++;
    }

    if (elem->nrvertices == 3)
      RenderTriangularElement(elem->vertex, m, n);
    else
      RenderQuadrilateralElement(elem->vertex, m, n);
    return;
  }

  verts[0] = *(elem->vertex[0]->point);
  verts[1] = *(elem->vertex[1]->point);
  verts[2] = *(elem->vertex[2]->point);
  if (elem->nrvertices > 3)
    verts[3] = *(elem->vertex[3]->point);

  if (renderopts.smooth_shading) {
    RGB vertcols[4];
    vertcols[0] = elem->vertex[0]->color;
    vertcols[1] = elem->vertex[1]->color;
    vertcols[2] = elem->vertex[2]->color;
    if (elem->nrvertices > 3)
      vertcols[3] = elem->vertex[3]->color;
    
    RenderPolygonGouraud(elem->nrvertices, verts, vertcols);
  } else {
    RGB color = ElementColor(elem);

    RenderSetColor(&color);
    RenderPolygonFlat(elem->nrvertices, verts);
  }

  if (renderopts.draw_outlines)
    RenderElementOutline(elem);
}

COLOR ElementDisplayRadiance(ELEMENT *elem)
{
  COLOR rad;
  COLORSUBTRACT(elem->rad[0], elem->source_rad, rad);

  if (mcr.show != SHOW_INDIRECT_RADIANCE) {
    /* source_rad is self-emitted radiance if !mcr.indirect_only. It is direct
     * illumination if mcr.direct_only */
    COLORADD(rad, elem->source_rad, rad);
    if (mcr.indirect_only || mcr.do_nondiffuse_first_shot) {
      /* add self-emitted radiance */
      COLORADD(rad, elem->Ed, rad);
    }
  }
  return rad;
}

COLOR ElementDisplayRadianceAtPoint(ELEMENT *elem, double u, double v)
{
  COLOR radiance;
  if (elem->basis->size == 1) {
    if (renderopts.smooth_shading) {
      /* do Gouraud interpolation if required */
      int i;
      COLOR rad[4];
      for (i=0; i<elem->nrvertices; i++)
	rad[i] = VertexRadiance(elem->vertex[i]);
      switch (elem->nrvertices) {
      case 3:
	COLORINTERPOLATEBARYCENTRIC(rad[0], rad[1], rad[2], u, v, radiance);
	break;
      case 4:
	COLORINTERPOLATEBILINEAR(rad[0], rad[1], rad[2], rad[3], u, v, radiance);
	break;
      default:
	Fatal(-1, "ElementDisplayRadianceAtPoint", "can only handle triangular or quadrilateral elements");
	COLORCLEAR(radiance);
      }
    } else {	/* flat shading */
      radiance = ElementDisplayRadiance(elem);
    }
  } else {	/* higher order approximations */
    radiance = ColorAtUV(elem->basis, elem->rad, u, v);
    if (mcr.show == SHOW_INDIRECT_RADIANCE) {
      COLORSUBTRACT(radiance, elem->source_rad, radiance);
    }
  }
  return radiance;
}