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gimp/plug-ins/map-object/map-object-shade.c

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/*****************/
/* Shading stuff */
/*****************/
#include "config.h"
#include <string.h>
#include <libgimp/gimp.h>
#include <libgimp/gimpui.h>
#include "map-object-apply.h"
#include "map-object-main.h"
#include "map-object-image.h"
#include "map-object-shade.h"
static gdouble bx1, by1, bx2, by2;
get_ray_color_func get_ray_color;
typedef struct
{
gdouble u, v;
gdouble t;
GimpVector3 s;
GimpVector3 n;
gint face;
} FaceIntersectInfo;
/*****************/
/* Phong shading */
/*****************/
static GimpRGB
phong_shade (GimpVector3 *pos,
GimpVector3 *viewpoint,
GimpVector3 *normal,
GimpRGB *diff_col,
GimpRGB *spec_col,
LightType type)
{
GimpRGB ambientcolor, diffusecolor, specularcolor;
gdouble NL, RV, dist;
GimpVector3 L, NN, V, N;
GimpVector3 *light;
light = mapvals.lightsource.type == DIRECTIONAL_LIGHT
? &mapvals.lightsource.direction
: &mapvals.lightsource.position,
/* Compute ambient intensity */
/* ========================= */
N = *normal;
ambientcolor = *diff_col;
gimp_rgb_multiply (&ambientcolor, mapvals.material.ambient_int);
/* Compute (N*L) term of Phong's equation */
/* ====================================== */
if (type == POINT_LIGHT)
gimp_vector3_sub (&L, light, pos);
else
L = *light;
dist = gimp_vector3_length (&L);
if (dist != 0.0)
gimp_vector3_mul (&L, 1.0 / dist);
NL = 2.0 * gimp_vector3_inner_product (&N, &L);
if (NL >= 0.0)
{
/* Compute (R*V)^alpha term of Phong's equation */
/* ============================================ */
gimp_vector3_sub (&V, viewpoint, pos);
gimp_vector3_normalize (&V);
gimp_vector3_mul (&N, NL);
gimp_vector3_sub (&NN, &N, &L);
RV = gimp_vector3_inner_product (&NN, &V);
RV = 0.0 < RV ? pow (RV, mapvals.material.highlight) : 0.0;
/* Compute diffuse and specular intensity contribution */
/* =================================================== */
diffusecolor = *diff_col;
gimp_rgb_multiply (&diffusecolor, mapvals.material.diffuse_ref);
gimp_rgb_multiply (&diffusecolor, NL);
specularcolor = *spec_col;
gimp_rgb_multiply (&specularcolor, mapvals.material.specular_ref);
gimp_rgb_multiply (&specularcolor, RV);
gimp_rgb_add (&diffusecolor, &specularcolor);
gimp_rgb_multiply (&diffusecolor, mapvals.material.diffuse_int);
gimp_rgb_clamp (&diffusecolor);
gimp_rgb_add (&ambientcolor, &diffusecolor);
}
return ambientcolor;
}
static gint
plane_intersect (GimpVector3 *dir,
GimpVector3 *viewp,
GimpVector3 *ipos,
gdouble *u,
gdouble *v)
{
static gdouble det, det1, det2, det3, t;
imat[0][0] = dir->x;
imat[1][0] = dir->y;
imat[2][0] = dir->z;
/* Compute determinant of the first 3x3 sub matrix (denominator) */
/* ============================================================= */
det = (imat[0][0] * imat[1][1] * imat[2][2] +
imat[0][1] * imat[1][2] * imat[2][0] +
imat[0][2] * imat[1][0] * imat[2][1] -
imat[0][2] * imat[1][1] * imat[2][0] -
imat[0][0] * imat[1][2] * imat[2][1] -
imat[2][2] * imat[0][1] * imat[1][0]);
/* If the determinant is non-zero, a intersection point exists */
/* =========================================================== */
if (det != 0.0)
{
/* Now, lets compute the numerator determinants (wow ;) */
/* ==================================================== */
det1 = (imat[0][3] * imat[1][1] * imat[2][2] +
imat[0][1] * imat[1][2] * imat[2][3] +
imat[0][2] * imat[1][3] * imat[2][1] -
imat[0][2] * imat[1][1] * imat[2][3] -
imat[1][2] * imat[2][1] * imat[0][3] -
imat[2][2] * imat[0][1] * imat[1][3]);
det2 = (imat[0][0] * imat[1][3] * imat[2][2] +
imat[0][3] * imat[1][2] * imat[2][0] +
imat[0][2] * imat[1][0] * imat[2][3] -
imat[0][2] * imat[1][3] * imat[2][0] -
imat[1][2] * imat[2][3] * imat[0][0] -
imat[2][2] * imat[0][3] * imat[1][0]);
det3 = (imat[0][0] * imat[1][1] * imat[2][3] +
imat[0][1] * imat[1][3] * imat[2][0] +
imat[0][3] * imat[1][0] * imat[2][1] -
imat[0][3] * imat[1][1] * imat[2][0] -
imat[1][3] * imat[2][1] * imat[0][0] -
imat[2][3] * imat[0][1] * imat[1][0]);
/* Now we have the simultaneous solutions. Lets compute the unknowns */
/* (skip u&v if t is <0, this means the intersection is behind us) */
/* ================================================================ */
t = det1 / det;
if (t > 0.0)
{
*u = 1.0 + ((det2 / det) - 0.5);
*v = 1.0 + ((det3 / det) - 0.5);
ipos->x = viewp->x + t * dir->x;
ipos->y = viewp->y + t * dir->y;
ipos->z = viewp->z + t * dir->z;
return TRUE;
}
}
return FALSE;
}
/*****************************************************************************
* These routines computes the color of the surface
* of the plane at a given point
*****************************************************************************/
GimpRGB
get_ray_color_plane (GimpVector3 *pos)
{
GimpRGB color = background;
static gint inside = FALSE;
static GimpVector3 ray, spos;
static gdouble vx, vy;
/* Construct a line from our VP to the point */
/* ========================================= */
gimp_vector3_sub (&ray, pos, &mapvals.viewpoint);
gimp_vector3_normalize (&ray);
/* Check for intersection. This is a quasi ray-tracer. */
/* =================================================== */
if (plane_intersect (&ray, &mapvals.viewpoint, &spos, &vx, &vy) == TRUE)
{
color = get_image_color (vx, vy, &inside);
if (color.a != 0.0 && inside == TRUE &&
mapvals.lightsource.type != NO_LIGHT)
{
/* Compute shading at this point */
/* ============================= */
color = phong_shade (&spos,
&mapvals.viewpoint,
&mapvals.normal,
&color,
&mapvals.lightsource.color,
mapvals.lightsource.type);
gimp_rgb_clamp (&color);
}
}
if (mapvals.transparent_background == FALSE && color.a < 1.0)
{
gimp_rgb_composite (&color, &background,
GIMP_RGB_COMPOSITE_BEHIND);
}
return color;
}
/***********************************************************************/
/* Given the NorthPole, Equator and a third vector (normal) compute */
/* the conversion from spherical oordinates to image space coordinates */
/***********************************************************************/
static void
sphere_to_image (GimpVector3 *normal,
gdouble *u,
gdouble *v)
{
static gdouble alpha, fac;
static GimpVector3 cross_prod;
alpha = acos (-gimp_vector3_inner_product (&mapvals.secondaxis, normal));
*v = alpha / G_PI;
if (*v == 0.0 || *v == 1.0)
{
*u = 0.0;
}
else
{
fac = (gimp_vector3_inner_product (&mapvals.firstaxis, normal) /
sin (alpha));
/* Make sure that we map to -1.0..1.0 (take care of rounding errors) */
/* ================================================================= */
fac = CLAMP (fac, -1.0, 1.0);
*u = acos (fac) / (2.0 * G_PI);
cross_prod = gimp_vector3_cross_product (&mapvals.secondaxis,
&mapvals.firstaxis);
if (gimp_vector3_inner_product (&cross_prod, normal) < 0.0)
*u = 1.0 - *u;
}
}
/***************************************************/
/* Compute intersection point with sphere (if any) */
/***************************************************/
static gint
sphere_intersect (GimpVector3 *dir,
GimpVector3 *viewp,
GimpVector3 *spos1,
GimpVector3 *spos2)
{
static gdouble alpha, beta, tau, s1, s2, tmp;
static GimpVector3 t;
gimp_vector3_sub (&t, &mapvals.position, viewp);
alpha = gimp_vector3_inner_product (dir, &t);
beta = gimp_vector3_inner_product (&t, &t);
tau = alpha * alpha - beta + mapvals.radius * mapvals.radius;
if (tau >= 0.0)
{
tau = sqrt (tau);
s1 = alpha + tau;
s2 = alpha - tau;
if (s2 < s1)
{
tmp = s1;
s1 = s2;
s2 = tmp;
}
spos1->x = viewp->x + s1 * dir->x;
spos1->y = viewp->y + s1 * dir->y;
spos1->z = viewp->z + s1 * dir->z;
spos2->x = viewp->x + s2 * dir->x;
spos2->y = viewp->y + s2 * dir->y;
spos2->z = viewp->z + s2 * dir->z;
return TRUE;
}
return FALSE;
}
/*****************************************************************************
* These routines computes the color of the surface
* of the sphere at a given point
*****************************************************************************/
GimpRGB
get_ray_color_sphere (GimpVector3 *pos)
{
GimpRGB color = background;
static GimpRGB color2;
static gint inside = FALSE;
static GimpVector3 normal, ray, spos1, spos2;
static gdouble vx, vy;
/* Check if ray is within the bounding box */
/* ======================================= */
if (pos->x<bx1 || pos->x>bx2 || pos->y<by1 || pos->y>by2)
return color;
/* Construct a line from our VP to the point */
/* ========================================= */
gimp_vector3_sub (&ray, pos, &mapvals.viewpoint);
gimp_vector3_normalize (&ray);
/* Check for intersection. This is a quasi ray-tracer. */
/* =================================================== */
if (sphere_intersect (&ray, &mapvals.viewpoint, &spos1, &spos2) == TRUE)
{
/* Compute spherical to rectangular mapping */
/* ======================================== */
gimp_vector3_sub (&normal, &spos1, &mapvals.position);
gimp_vector3_normalize (&normal);
sphere_to_image (&normal, &vx, &vy);
color = get_image_color (vx, vy, &inside);
/* Check for total transparency... */
/* =============================== */
if (color.a < 1.0)
{
/* Hey, we can see through here! */
/* Lets see what's on the other side.. */
/* =================================== */
color = phong_shade (&spos1,
&mapvals.viewpoint,
&normal,
&color,
&mapvals.lightsource.color,
mapvals.lightsource.type);
gimp_rgb_clamp (&color);
gimp_vector3_sub (&normal, &spos2, &mapvals.position);
gimp_vector3_normalize (&normal);
sphere_to_image (&normal, &vx, &vy);
color2 = get_image_color (vx, vy, &inside);
/* Make the normal point inwards */
/* ============================= */
gimp_vector3_mul (&normal, -1.0);
color2 = phong_shade (&spos2,
&mapvals.viewpoint,
&normal,
&color2,
&mapvals.lightsource.color,
mapvals.lightsource.type);
gimp_rgb_clamp (&color2);
/* Compute a mix of the first and second colors */
/* ============================================ */
gimp_rgb_composite (&color, &color2, GIMP_RGB_COMPOSITE_NORMAL);
gimp_rgb_clamp (&color);
}
else if (color.a != 0.0 &&
inside == TRUE &&
mapvals.lightsource.type != NO_LIGHT)
{
/* Compute shading at this point */
/* ============================= */
color = phong_shade (&spos1,
&mapvals.viewpoint,
&normal,
&color,
&mapvals.lightsource.color,
mapvals.lightsource.type);
gimp_rgb_clamp (&color);
}
}
if (mapvals.transparent_background == FALSE && color.a < 1.0)
{
gimp_rgb_composite (&color, &background,
GIMP_RGB_COMPOSITE_BEHIND);
}
return color;
}
/***************************************************/
/* Transform the corners of the bounding box to 2D */
/***************************************************/
void
compute_bounding_box (void)
{
GimpVector3 p1, p2;
gdouble t;
GimpVector3 dir;
p1 = mapvals.position;
p1.x -= (mapvals.radius + 0.01);
p1.y -= (mapvals.radius + 0.01);
p2 = mapvals.position;
p2.x += (mapvals.radius + 0.01);
p2.y += (mapvals.radius + 0.01);
gimp_vector3_sub (&dir, &p1, &mapvals.viewpoint);
gimp_vector3_normalize (&dir);
if (dir.z != 0.0)
{
t = (-1.0 * mapvals.viewpoint.z) / dir.z;
p1.x = (mapvals.viewpoint.x + t * dir.x);
p1.y = (mapvals.viewpoint.y + t * dir.y);
}
gimp_vector3_sub (&dir, &p2, &mapvals.viewpoint);
gimp_vector3_normalize (&dir);
if (dir.z != 0.0)
{
t = (-1.0 * mapvals.viewpoint.z) / dir.z;
p2.x = (mapvals.viewpoint.x + t * dir.x);
p2.y = (mapvals.viewpoint.y + t * dir.y);
}
bx1 = p1.x;
by1 = p1.y;
bx2 = p2.x;
by2 = p2.y;
}
/* These two were taken from the Mesa source. Mesa is written */
/* and is (C) by Brian Paul. vecmulmat() performs a post-mul by */
/* a 4x4 matrix to a 1x4(3) vector. rotmat() creates a matrix */
/* that by post-mul will rotate a 1x4(3) vector the given angle */
/* about the given axis. */
/* ============================================================ */
void
vecmulmat (GimpVector3 *u,
GimpVector3 *v,
gfloat m[16])
{
gfloat v0=v->x, v1=v->y, v2=v->z;
#define M(row,col) m[col*4+row]
u->x = v0 * M(0,0) + v1 * M(1,0) + v2 * M(2,0) + M(3,0);
u->y = v0 * M(0,1) + v1 * M(1,1) + v2 * M(2,1) + M(3,1);
u->z = v0 * M(0,2) + v1 * M(1,2) + v2 * M(2,2) + M(3,2);
#undef M
}
void
rotatemat (gfloat angle,
GimpVector3 *v,
gfloat m[16])
{
/* This function contributed by Erich Boleyn (erich@uruk.org) */
gfloat mag, s, c;
gfloat xx, yy, zz, xy, yz, zx, xs, ys, zs, one_c;
gfloat IdentityMat[16];
gint cnt;
s = sin (angle * (G_PI / 180.0));
c = cos (angle * (G_PI / 180.0));
mag = sqrt (v->x*v->x + v->y*v->y + v->z*v->z);
if (mag == 0.0)
{
/* generate an identity matrix and return */
for (cnt = 0; cnt < 16; cnt++)
IdentityMat[cnt] = 0.0;
IdentityMat[0] = 1.0;
IdentityMat[5] = 1.0;
IdentityMat[10] = 1.0;
IdentityMat[15] = 1.0;
memcpy (m, IdentityMat, sizeof (gfloat) * 16);
return;
}
v->x /= mag;
v->y /= mag;
v->z /= mag;
#define M(row,col) m[col*4+row]
xx = v->x * v->x;
yy = v->y * v->y;
zz = v->z * v->z;
xy = v->x * v->y;
yz = v->y * v->z;
zx = v->z * v->x;
xs = v->x * s;
ys = v->y * s;
zs = v->z * s;
one_c = 1.0F - c;
M(0,0) = (one_c * xx) + c;
M(0,1) = (one_c * xy) - zs;
M(0,2) = (one_c * zx) + ys;
M(0,3) = 0.0F;
M(1,0) = (one_c * xy) + zs;
M(1,1) = (one_c * yy) + c;
M(1,2) = (one_c * yz) - xs;
M(1,3) = 0.0F;
M(2,0) = (one_c * zx) - ys;
M(2,1) = (one_c * yz) + xs;
M(2,2) = (one_c * zz) + c;
M(2,3) = 0.0F;
M(3,0) = 0.0F;
M(3,1) = 0.0F;
M(3,2) = 0.0F;
M(3,3) = 1.0F;
#undef M
}
/* Transpose the matrix m. If m is orthogonal (like a rotation matrix), */
/* this is equal to the inverse of the matrix. */
/* ==================================================================== */
void
transpose_mat (gfloat m[16])
{
gint i, j;
gfloat t;
for (i = 0; i < 4; i++)
{
for (j = 0; j < i; j++)
{
t = m[j*4+i];
m[j*4+i] = m[i*4+j];
m[i*4+j] = t;
}
}
}
/* Compute the matrix product c=a*b */
/* ================================ */
void
matmul (gfloat a[16],
gfloat b[16],
gfloat c[16])
{
gint i, j, k;
gfloat value;
#define A(row,col) a[col*4+row]
#define B(row,col) b[col*4+row]
#define C(row,col) c[col*4+row]
for (i = 0; i < 4; i++)
{
for (j = 0; j < 4; j++)
{
value = 0.0;
for (k = 0; k < 4; k++)
value += A(i,k) * B(k,j);
C(i,j) = value;
}
}
#undef A
#undef B
#undef C
}
void
ident_mat (gfloat m[16])
{
gint i, j;
#define M(row,col) m[col*4+row]
for (i = 0; i < 4; i++)
{
for (j = 0; j < 4; j++)
{
if (i == j)
M(i,j) = 1.0;
else
M(i,j) = 0.0;
}
}
#undef M
}
static gboolean
intersect_rect (gdouble u,
gdouble v,
gdouble w,
GimpVector3 viewp,
GimpVector3 dir,
FaceIntersectInfo *face_info)
{
gboolean result = FALSE;
gdouble u2, v2;
if (dir.z!=0.0)
{
u2 = u / 2.0;
v2 = v / 2.0;
face_info->t = (w-viewp.z) / dir.z;
face_info->s.x = viewp.x + face_info->t * dir.x;
face_info->s.y = viewp.y + face_info->t * dir.y;
face_info->s.z = w;
if (face_info->s.x >= -u2 && face_info->s.x <= u2 &&
face_info->s.y >= -v2 && face_info->s.y <= v2)
{
face_info->u = (face_info->s.x + u2) / u;
face_info->v = (face_info->s.y + v2) / v;
result = TRUE;
}
}
return result;
}
static gboolean
intersect_box (GimpVector3 scale,
GimpVector3 viewp,
GimpVector3 dir,
FaceIntersectInfo *face_intersect)
{
GimpVector3 v, d, tmp, axis[3];
FaceIntersectInfo face_tmp;
gboolean result = FALSE;
gfloat m[16];
gint i = 0;
gimp_vector3_set (&axis[0], 1.0, 0.0, 0.0);
gimp_vector3_set (&axis[1], 0.0, 1.0, 0.0);
gimp_vector3_set (&axis[2], 0.0, 0.0, 1.0);
/* Front side */
/* ========== */
if (intersect_rect (scale.x, scale.y, scale.z / 2.0,
viewp, dir, &face_intersect[i]) == TRUE)
{
face_intersect[i].face = 0;
gimp_vector3_set (&face_intersect[i++].n, 0.0, 0.0, 1.0);
result = TRUE;
}
/* Back side */
/* ========= */
if (intersect_rect (scale.x, scale.y, -scale.z / 2.0,
viewp, dir, &face_intersect[i]) == TRUE)
{
face_intersect[i].face = 1;
face_intersect[i].u = 1.0 - face_intersect[i].u;
gimp_vector3_set (&face_intersect[i++].n, 0.0, 0.0, -1.0);
result = TRUE;
}
/* Check if we've found the two possible intersection points */
/* ========================================================= */
if (i < 2)
{
/* Top: Rotate viewpoint and direction into rectangle's local coordinate system */
/* ============================================================================ */
rotatemat (90, &axis[0], m);
vecmulmat (&v, &viewp, m);
vecmulmat (&d, &dir, m);
if (intersect_rect (scale.x, scale.z, scale.y / 2.0,
v, d, &face_intersect[i]) == TRUE)
{
face_intersect[i].face = 2;
transpose_mat (m);
vecmulmat(&tmp, &face_intersect[i].s, m);
face_intersect[i].s = tmp;
gimp_vector3_set (&face_intersect[i++].n, 0.0, -1.0, 0.0);
result = TRUE;
}
}
/* Check if we've found the two possible intersection points */
/* ========================================================= */
if (i < 2)
{
/* Bottom: Rotate viewpoint and direction into rectangle's local coordinate system */
/* =============================================================================== */
rotatemat (90, &axis[0], m);
vecmulmat (&v, &viewp, m);
vecmulmat (&d, &dir, m);
if (intersect_rect (scale.x, scale.z, -scale.y / 2.0,
v, d, &face_intersect[i]) == TRUE)
{
face_intersect[i].face = 3;
transpose_mat (m);
vecmulmat (&tmp, &face_intersect[i].s, m);
face_intersect[i].s = tmp;
face_intersect[i].v = 1.0 - face_intersect[i].v;
gimp_vector3_set (&face_intersect[i++].n, 0.0, 1.0, 0.0);
result = TRUE;
}
}
/* Check if we've found the two possible intersection points */
/* ========================================================= */
if (i < 2)
{
/* Left side: Rotate viewpoint and direction into rectangle's local coordinate system */
/* ================================================================================== */
rotatemat (90, &axis[1], m);
vecmulmat (&v, &viewp, m);
vecmulmat (&d, &dir, m);
if (intersect_rect (scale.z, scale.y, scale.x / 2.0,
v, d, &face_intersect[i]) == TRUE)
{
face_intersect[i].face = 4;
transpose_mat (m);
vecmulmat (&tmp, &face_intersect[i].s, m);
face_intersect[i].s = tmp;
gimp_vector3_set (&face_intersect[i++].n, 1.0, 0.0, 0.0);
result = TRUE;
}
}
/* Check if we've found the two possible intersection points */
/* ========================================================= */
if (i < 2)
{
/* Right side: Rotate viewpoint and direction into rectangle's local coordinate system */
/* =================================================================================== */
rotatemat (90, &axis[1], m);
vecmulmat (&v, &viewp, m);
vecmulmat (&d, &dir, m);
if (intersect_rect (scale.z, scale.y, -scale.x / 2.0,
v, d, &face_intersect[i]) == TRUE)
{
face_intersect[i].face = 5;
transpose_mat (m);
vecmulmat (&tmp, &face_intersect[i].s, m);
face_intersect[i].u = 1.0 - face_intersect[i].u;
gimp_vector3_set (&face_intersect[i++].n, -1.0, 0.0, 0.0);
result = TRUE;
}
}
/* Sort intersection points */
/* ======================== */
if (face_intersect[0].t > face_intersect[1].t)
{
face_tmp = face_intersect[0];
face_intersect[0] = face_intersect[1];
face_intersect[1] = face_tmp;
}
return result;
}
GimpRGB
get_ray_color_box (GimpVector3 *pos)
{
GimpVector3 lvp, ldir, vp, p, dir, ns, nn;
GimpRGB color, color2;
gfloat m[16];
gint i;
FaceIntersectInfo face_intersect[2];
color = background;
vp = mapvals.viewpoint;
p = *pos;
/* Translate viewpoint so that the box has its origin */
/* at its lower left corner. */
/* ================================================== */
vp.x = vp.x - mapvals.position.x;
vp.y = vp.y - mapvals.position.y;
vp.z = vp.z - mapvals.position.z;
p.x = p.x - mapvals.position.x;
p.y = p.y - mapvals.position.y;
p.z = p.z - mapvals.position.z;
/* Compute direction */
/* ================= */
gimp_vector3_sub (&dir, &p, &vp);
gimp_vector3_normalize (&dir);
/* Compute inverse of rotation matrix and apply it to */
/* the viewpoint and direction. This transforms the */
/* observer into the local coordinate system of the box */
/* ==================================================== */
memcpy (m, rotmat, sizeof (gfloat) * 16);
transpose_mat (m);
vecmulmat (&lvp, &vp, m);
vecmulmat (&ldir, &dir, m);
/* Ok. Now the observer is in the space where the box is located */
/* with its lower left corner at the origin and its axis aligned */
/* to the cartesian basis. Check if the transformed ray hits it. */
/* ============================================================= */
face_intersect[0].t = 1000000.0;
face_intersect[1].t = 1000000.0;
if (intersect_box (mapvals.scale, lvp, ldir, face_intersect) == TRUE)
{
/* We've hit the box. Transform the hit points and */
/* normals back into the world coordinate system */
/* =============================================== */
for (i = 0; i < 2; i++)
{
vecmulmat (&ns, &face_intersect[i].s, rotmat);
vecmulmat (&nn, &face_intersect[i].n, rotmat);
ns.x = ns.x + mapvals.position.x;
ns.y = ns.y + mapvals.position.y;
ns.z = ns.z + mapvals.position.z;
face_intersect[i].s = ns;
face_intersect[i].n = nn;
}
color = get_box_image_color (face_intersect[0].face,
face_intersect[0].u,
face_intersect[0].v);
/* Check for total transparency... */
/* =============================== */
if (color.a < 1.0)
{
/* Hey, we can see through here! */
/* Lets see what's on the other side.. */
/* =================================== */
color = phong_shade (&face_intersect[0].s,
&mapvals.viewpoint,
&face_intersect[0].n,
&color,
&mapvals.lightsource.color,
mapvals.lightsource.type);
gimp_rgb_clamp (&color);
color2 = get_box_image_color (face_intersect[1].face,
face_intersect[1].u,
face_intersect[1].v);
/* Make the normal point inwards */
/* ============================= */
gimp_vector3_mul (&face_intersect[1].n, -1.0);
color2 = phong_shade (&face_intersect[1].s,
&mapvals.viewpoint,
&face_intersect[1].n,
&color2,
&mapvals.lightsource.color,
mapvals.lightsource.type);
gimp_rgb_clamp (&color2);
if (mapvals.transparent_background == FALSE && color2.a < 1.0)
{
gimp_rgb_composite (&color2, &background,
GIMP_RGB_COMPOSITE_BEHIND);
}
/* Compute a mix of the first and second colors */
/* ============================================ */
gimp_rgb_composite (&color, &color2, GIMP_RGB_COMPOSITE_NORMAL);
gimp_rgb_clamp (&color);
}
else if (color.a != 0.0 && mapvals.lightsource.type != NO_LIGHT)
{
color = phong_shade (&face_intersect[0].s,
&mapvals.viewpoint,
&face_intersect[0].n,
&color,
&mapvals.lightsource.color,
mapvals.lightsource.type);
gimp_rgb_clamp (&color);
}
}
else
{
if (mapvals.transparent_background == TRUE)
gimp_rgb_set_alpha (&color, 0.0);
}
return color;
}
static gboolean
intersect_circle (GimpVector3 vp,
GimpVector3 dir,
gdouble w,
FaceIntersectInfo *face_info)
{
gboolean result = FALSE;
gdouble r, d;
#define sqr(a) (a*a)
if (dir.y != 0.0)
{
face_info->t = (w-vp.y)/dir.y;
face_info->s.x = vp.x + face_info->t*dir.x;
face_info->s.y = w;
face_info->s.z = vp.z + face_info->t*dir.z;
r = sqrt (sqr (face_info->s.x) + sqr (face_info->s.z));
if (r <= mapvals.cylinder_radius)
{
d = 2.0 * mapvals.cylinder_radius;
face_info->u = (face_info->s.x + mapvals.cylinder_radius) / d;
face_info->v = (face_info->s.z + mapvals.cylinder_radius) / d;
result = TRUE;
}
}
#undef sqr
return result;
}
static gboolean
intersect_cylinder (GimpVector3 vp,
GimpVector3 dir,
FaceIntersectInfo *face_intersect)
{
gdouble a, b, c, d, e, f, tmp, l;
gboolean result = FALSE;
gint i;
#define sqr(a) (a*a)
a = sqr (dir.x) + sqr (dir.z);
b = 2.0 * (vp.x * dir.x + vp.z * dir.z);
c = sqr (vp.x) + sqr (vp.z) - sqr (mapvals.cylinder_radius);
d = sqr (b) - 4.0 * a * c;
if (d >= 0.0)
{
e = sqrt (d);
f = 2.0 * a;
if (f != 0.0)
{
result = TRUE;
face_intersect[0].t = (-b+e)/f;
face_intersect[1].t = (-b-e)/f;
if (face_intersect[0].t>face_intersect[1].t)
{
tmp = face_intersect[0].t;
face_intersect[0].t = face_intersect[1].t;
face_intersect[1].t = tmp;
}
for (i = 0; i < 2; i++)
{
face_intersect[i].s.x = vp.x + face_intersect[i].t * dir.x;
face_intersect[i].s.y = vp.y + face_intersect[i].t * dir.y;
face_intersect[i].s.z = vp.z + face_intersect[i].t * dir.z;
face_intersect[i].n = face_intersect[i].s;
face_intersect[i].n.y = 0.0;
gimp_vector3_normalize(&face_intersect[i].n);
l = mapvals.cylinder_length/2.0;
face_intersect[i].u = (atan2(face_intersect[i].s.x,face_intersect[i].s.z)+G_PI)/(2.0*G_PI);
face_intersect[i].v = (face_intersect[i].s.y+l)/mapvals.cylinder_length;
/* Mark hitpoint as on the cylinder hull */
/* ===================================== */
face_intersect[i].face = 0;
/* Check if we're completely off the cylinder axis */
/* =============================================== */
if (face_intersect[i].s.y>l || face_intersect[i].s.y<-l)
{
/* Check if we've hit a cap */
/* ======================== */
if (face_intersect[i].s.y>l)
{
if (intersect_circle(vp,dir,l,&face_intersect[i])==FALSE)
result = FALSE;
else
{
face_intersect[i].face = 2;
face_intersect[i].v = 1 - face_intersect[i].v;
gimp_vector3_set(&face_intersect[i].n, 0.0, 1.0, 0.0);
}
}
else
{
if (intersect_circle(vp,dir,-l,&face_intersect[i])==FALSE)
result = FALSE;
else
{
face_intersect[i].face = 1;
gimp_vector3_set(&face_intersect[i].n, 0.0, -1.0, 0.0);
}
}
}
}
}
}
#undef sqr
return result;
}
static GimpRGB
get_cylinder_color (gint face,
gdouble u,
gdouble v)
{
GimpRGB color;
gint inside;
if (face == 0)
color = get_image_color (u, v, &inside);
else
color = get_cylinder_image_color (face - 1, u, v);
return color;
}
GimpRGB
get_ray_color_cylinder (GimpVector3 *pos)
{
GimpVector3 lvp, ldir, vp, p, dir, ns, nn;
GimpRGB color, color2;
gfloat m[16];
gint i;
FaceIntersectInfo face_intersect[2];
color = background;
vp = mapvals.viewpoint;
p = *pos;
vp.x = vp.x - mapvals.position.x;
vp.y = vp.y - mapvals.position.y;
vp.z = vp.z - mapvals.position.z;
p.x = p.x - mapvals.position.x;
p.y = p.y - mapvals.position.y;
p.z = p.z - mapvals.position.z;
/* Compute direction */
/* ================= */
gimp_vector3_sub (&dir, &p, &vp);
gimp_vector3_normalize (&dir);
/* Compute inverse of rotation matrix and apply it to */
/* the viewpoint and direction. This transforms the */
/* observer into the local coordinate system of the box */
/* ==================================================== */
memcpy (m, rotmat, sizeof (gfloat) * 16);
transpose_mat (m);
vecmulmat (&lvp, &vp, m);
vecmulmat (&ldir, &dir, m);
if (intersect_cylinder (lvp, ldir, face_intersect) == TRUE)
{
/* We've hit the cylinder. Transform the hit points and */
/* normals back into the world coordinate system */
/* ==================================================== */
for (i = 0; i < 2; i++)
{
vecmulmat (&ns, &face_intersect[i].s, rotmat);
vecmulmat (&nn, &face_intersect[i].n, rotmat);
ns.x = ns.x + mapvals.position.x;
ns.y = ns.y + mapvals.position.y;
ns.z = ns.z + mapvals.position.z;
face_intersect[i].s = ns;
face_intersect[i].n = nn;
}
color = get_cylinder_color (face_intersect[0].face,
face_intersect[0].u,
face_intersect[0].v);
/* Check for transparency... */
/* ========================= */
if (color.a < 1.0)
{
/* Hey, we can see through here! */
/* Lets see what's on the other side.. */
/* =================================== */
color = phong_shade (&face_intersect[0].s,
&mapvals.viewpoint,
&face_intersect[0].n,
&color,
&mapvals.lightsource.color,
mapvals.lightsource.type);
gimp_rgb_clamp (&color);
color2 = get_cylinder_color (face_intersect[1].face,
face_intersect[1].u,
face_intersect[1].v);
/* Make the normal point inwards */
/* ============================= */
gimp_vector3_mul (&face_intersect[1].n, -1.0);
color2 = phong_shade (&face_intersect[1].s,
&mapvals.viewpoint,
&face_intersect[1].n,
&color2,
&mapvals.lightsource.color,
mapvals.lightsource.type);
gimp_rgb_clamp (&color2);
if (mapvals.transparent_background == FALSE && color2.a < 1.0)
{
gimp_rgb_composite (&color2, &background,
GIMP_RGB_COMPOSITE_BEHIND);
}
/* Compute a mix of the first and second colors */
/* ============================================ */
gimp_rgb_composite (&color, &color2, GIMP_RGB_COMPOSITE_NORMAL);
gimp_rgb_clamp (&color);
}
else if (color.a != 0.0 && mapvals.lightsource.type != NO_LIGHT)
{
color = phong_shade (&face_intersect[0].s,
&mapvals.viewpoint,
&face_intersect[0].n,
&color,
&mapvals.lightsource.color,
mapvals.lightsource.type);
gimp_rgb_clamp (&color);
}
}
else
{
if (mapvals.transparent_background == TRUE)
gimp_rgb_set_alpha (&color, 0.0);
}
return color;
}
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