gimp/libgimpmath/gimpvector.c

1070 lines
27 KiB
C

/* LIBGIMP - The GIMP Library
* Copyright (C) 1995-1997 Peter Mattis and Spencer Kimball
*
* gimpvector.c
*
* The gimp_vector* functions were taken from:
* GCK - The General Convenience Kit
* Copyright (C) 1996 Tom Bech
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
/**********************************************/
/* A little collection of useful vector stuff */
/**********************************************/
#include "config.h"
#include <glib-object.h>
#include "gimpmath.h"
/*************************/
/* Some useful constants */
/*************************/
static const GimpVector2 gimp_vector2_zero = { 0.0, 0.0 };
static const GimpVector2 gimp_vector2_unit_x = { 1.0, 0.0 };
static const GimpVector2 gimp_vector2_unit_y = { 0.0, 1.0 };
static const GimpVector3 gimp_vector3_zero = { 0.0, 0.0, 0.0 };
static const GimpVector3 gimp_vector3_unit_x = { 1.0, 0.0, 0.0 };
static const GimpVector3 gimp_vector3_unit_y = { 0.0, 1.0, 0.0 };
static const GimpVector3 gimp_vector3_unit_z = { 0.0, 0.0, 1.0 };
/**************************************/
/* Two dimensional vector functions */
/**************************************/
/**
* gimp_vector2_new:
* @x: the X coordinate.
* @y: the Y coordinate.
*
* Creates a #GimpVector2 of coordinates @x and @y.
*
* Returns: the resulting #GimpVector2.
**/
GimpVector2
gimp_vector2_new (gdouble x,
gdouble y)
{
GimpVector2 vector;
vector.x = x;
vector.y = y;
return vector;
}
/**
* gimp_vector2_set:
* @vector: a pointer to a #GimpVector2.
* @x: the X coordinate.
* @y: the Y coordinate.
*
* Sets the X and Y coordinates of @vector to @x and @y.
**/
void
gimp_vector2_set (GimpVector2 *vector,
gdouble x,
gdouble y)
{
vector->x = x;
vector->y = y;
}
/**
* gimp_vector2_length:
* @vector: a pointer to a #GimpVector2.
*
* Computes the length of a 2D vector.
*
* Returns: the length of @vector (a positive gdouble).
**/
gdouble
gimp_vector2_length (const GimpVector2 *vector)
{
return (sqrt (vector->x * vector->x + vector->y * vector->y));
}
/**
* gimp_vector2_length_val:
* @vector: a #GimpVector2.
*
* This function is identical to gimp_vector2_length() but the
* vector is passed by value rather than by reference.
*
* Returns: the length of @vector (a positive gdouble).
**/
gdouble
gimp_vector2_length_val (GimpVector2 vector)
{
return (sqrt (vector.x * vector.x + vector.y * vector.y));
}
/**
* gimp_vector2_mul:
* @vector: a pointer to a #GimpVector2.
* @factor: a scalar.
*
* Multiplies each component of the @vector by @factor. Note that this
* is equivalent to multiplying the vectors length by @factor.
**/
void
gimp_vector2_mul (GimpVector2 *vector,
gdouble factor)
{
vector->x *= factor;
vector->y *= factor;
}
/**
* gimp_vector2_mul_val:
* @vector: a #GimpVector2.
* @factor: a scalar.
*
* This function is identical to gimp_vector2_mul() but the vector is
* passed by value rather than by reference.
*
* Returns: the resulting #GimpVector2.
**/
GimpVector2
gimp_vector2_mul_val (GimpVector2 vector,
gdouble factor)
{
GimpVector2 result;
result.x = vector.x * factor;
result.y = vector.y * factor;
return result;
}
/**
* gimp_vector2_normalize:
* @vector: a pointer to a #GimpVector2.
*
* Normalizes the @vector so the length of the @vector is 1.0. The nul
* vector will not be changed.
**/
void
gimp_vector2_normalize (GimpVector2 *vector)
{
gdouble len;
len = gimp_vector2_length (vector);
if (len != 0.0)
{
len = 1.0 / len;
vector->x *= len;
vector->y *= len;
}
else
{
*vector = gimp_vector2_zero;
}
}
/**
* gimp_vector2_normalize_val:
* @vector: a #GimpVector2.
*
* This function is identical to gimp_vector2_normalize() but the
* vector is passed by value rather than by reference.
*
* Returns: a #GimpVector2 parallel to @vector, pointing in the same
* direction but with a length of 1.0.
**/
GimpVector2
gimp_vector2_normalize_val (GimpVector2 vector)
{
GimpVector2 normalized;
gdouble len;
len = gimp_vector2_length_val (vector);
if (len != 0.0)
{
len = 1.0 / len;
normalized.x = vector.x * len;
normalized.y = vector.y * len;
return normalized;
}
else
{
return gimp_vector2_zero;
}
}
/**
* gimp_vector2_neg:
* @vector: a pointer to a #GimpVector2.
*
* Negates the @vector (i.e. negate all its coordinates).
**/
void
gimp_vector2_neg (GimpVector2 *vector)
{
vector->x *= -1.0;
vector->y *= -1.0;
}
/**
* gimp_vector2_neg_val:
* @vector: a #GimpVector2.
*
* This function is identical to gimp_vector2_neg() but the vector
* is passed by value rather than by reference.
*
* Returns: the negated #GimpVector2.
**/
GimpVector2
gimp_vector2_neg_val (GimpVector2 vector)
{
GimpVector2 result;
result.x = vector.x * -1.0;
result.y = vector.y * -1.0;
return result;
}
/**
* gimp_vector2_add:
* @result: destination for the resulting #GimpVector2.
* @vector1: a pointer to the first #GimpVector2.
* @vector2: a pointer to the second #GimpVector2.
*
* Computes the sum of two 2D vectors. The resulting #GimpVector2 is
* stored in @result.
**/
void
gimp_vector2_add (GimpVector2 *result,
const GimpVector2 *vector1,
const GimpVector2 *vector2)
{
result->x = vector1->x + vector2->x;
result->y = vector1->y + vector2->y;
}
/**
* gimp_vector2_add_val:
* @vector1: the first #GimpVector2.
* @vector2: the second #GimpVector2.
*
* This function is identical to gimp_vector2_add() but the vectors
* are passed by value rather than by reference.
*
* Returns: the resulting #GimpVector2.
**/
GimpVector2
gimp_vector2_add_val (GimpVector2 vector1,
GimpVector2 vector2)
{
GimpVector2 result;
result.x = vector1.x + vector2.x;
result.y = vector1.y + vector2.y;
return result;
}
/**
* gimp_vector2_sub:
* @result: the destination for the resulting #GimpVector2.
* @vector1: a pointer to the first #GimpVector2.
* @vector2: a pointer to the second #GimpVector2.
*
* Computes the difference of two 2D vectors (@vector1 minus @vector2).
* The resulting #GimpVector2 is stored in @result.
**/
void
gimp_vector2_sub (GimpVector2 *result,
const GimpVector2 *vector1,
const GimpVector2 *vector2)
{
result->x = vector1->x - vector2->x;
result->y = vector1->y - vector2->y;
}
/**
* gimp_vector2_sub_val:
* @vector1: the first #GimpVector2.
* @vector2: the second #GimpVector2.
*
* This function is identical to gimp_vector2_sub() but the vectors
* are passed by value rather than by reference.
*
* Returns: the resulting #GimpVector2.
**/
GimpVector2
gimp_vector2_sub_val (GimpVector2 vector1,
GimpVector2 vector2)
{
GimpVector2 result;
result.x = vector1.x - vector2.x;
result.y = vector1.y - vector2.y;
return result;
}
/**
* gimp_vector2_inner_product:
* @vector1: a pointer to the first #GimpVector2.
* @vector2: a pointer to the second #GimpVector2.
*
* Computes the inner (dot) product of two 2D vectors.
* This product is zero if and only if the two vectors are orthognal.
*
* Returns: The inner product.
**/
gdouble
gimp_vector2_inner_product (const GimpVector2 *vector1,
const GimpVector2 *vector2)
{
return (vector1->x * vector2->x + vector1->y * vector2->y);
}
/**
* gimp_vector2_inner_product_val:
* @vector1: the first #GimpVector2.
* @vector2: the second #GimpVector2.
*
* This function is identical to gimp_vector2_inner_product() but the
* vectors are passed by value rather than by reference.
*
* Returns: The inner product.
**/
gdouble
gimp_vector2_inner_product_val (GimpVector2 vector1,
GimpVector2 vector2)
{
return (vector1.x * vector2.x + vector1.y * vector2.y);
}
/**
* gimp_vector2_cross_product:
* @vector1: a pointer to the first #GimpVector2.
* @vector2: a pointer to the second #GimpVector2.
*
* Compute the cross product of two vectors. The result is a
* #GimpVector2 which is orthognal to both @vector1 and @vector2. If
* @vector1 and @vector2 are parallel, the result will be the nul
* vector.
*
* Note that in 2D, this function is useful to test if two vectors are
* parallel or not, or to compute the area spawned by two vectors.
*
* Returns: The cross product.
**/
GimpVector2
gimp_vector2_cross_product (const GimpVector2 *vector1,
const GimpVector2 *vector2)
{
GimpVector2 normal;
normal.x = vector1->x * vector2->y - vector1->y * vector2->x;
normal.y = vector1->y * vector2->x - vector1->x * vector2->y;
return normal;
}
/**
* gimp_vector2_cross_product_val:
* @vector1: the first #GimpVector2.
* @vector2: the second #GimpVector2.
*
* This function is identical to gimp_vector2_cross_product() but the
* vectors are passed by value rather than by reference.
*
* Returns: The cross product.
**/
GimpVector2
gimp_vector2_cross_product_val (GimpVector2 vector1,
GimpVector2 vector2)
{
GimpVector2 normal;
normal.x = vector1.x * vector2.y - vector1.y * vector2.x;
normal.y = vector1.y * vector2.x - vector1.x * vector2.y;
return normal;
}
/**
* gimp_vector2_rotate:
* @vector: a pointer to a #GimpVector2.
* @alpha: an angle (in radians).
*
* Rotates the @vector counterclockwise by @alpha radians.
**/
void
gimp_vector2_rotate (GimpVector2 *vector,
gdouble alpha)
{
GimpVector2 result;
result.x = cos (alpha) * vector->x + sin (alpha) * vector->y;
result.y = cos (alpha) * vector->y - sin (alpha) * vector->x;
*vector = result;
}
/**
* gimp_vector2_rotate_val:
* @vector: a #GimpVector2.
* @alpha: an angle (in radians).
*
* This function is identical to gimp_vector2_rotate() but the vector
* is passed by value rather than by reference.
*
* Returns: a #GimpVector2 representing @vector rotated by @alpha
* radians.
**/
GimpVector2
gimp_vector2_rotate_val (GimpVector2 vector,
gdouble alpha)
{
GimpVector2 result;
result.x = cos (alpha) * vector.x + sin (alpha) * vector.y;
result.y = cos (alpha) * vector.y - sin (alpha) * vector.x;
return result;
}
/**************************************/
/* Three dimensional vector functions */
/**************************************/
/**
* gimp_vector3_new:
* @x: the X coordinate.
* @y: the Y coordinate.
* @z: the Z coordinate.
*
* Creates a #GimpVector3 of coordinate @x, @y and @z.
*
* Returns: the resulting #GimpVector3.
**/
GimpVector3
gimp_vector3_new (gdouble x,
gdouble y,
gdouble z)
{
GimpVector3 vector;
vector.x = x;
vector.y = y;
vector.z = z;
return vector;
}
/**
* gimp_vector3_set:
* @vector: a pointer to a #GimpVector3.
* @x: the X coordinate.
* @y: the Y coordinate.
* @z: the Z coordinate.
*
* Sets the X, Y and Z coordinates of @vector to @x, @y and @z.
**/
void
gimp_vector3_set (GimpVector3 *vector,
gdouble x,
gdouble y,
gdouble z)
{
vector->x = x;
vector->y = y;
vector->z = z;
}
/**
* gimp_vector3_length:
* @vector: a pointer to a #GimpVector3.
*
* Computes the length of a 3D vector.
*
* Returns: the length of @vector (a positive gdouble).
**/
gdouble
gimp_vector3_length (const GimpVector3 *vector)
{
return (sqrt (vector->x * vector->x +
vector->y * vector->y +
vector->z * vector->z));
}
/**
* gimp_vector3_length_val:
* @vector: a #GimpVector3.
*
* This function is identical to gimp_vector3_length() but the vector
* is passed by value rather than by reference.
*
* Returns: the length of @vector (a positive gdouble).
**/
gdouble
gimp_vector3_length_val (GimpVector3 vector)
{
return (sqrt (vector.x * vector.x +
vector.y * vector.y +
vector.z * vector.z));
}
/**
* gimp_vector3_mul:
* @vector: a pointer to a #GimpVector3.
* @factor: a scalar.
*
* Multiplies each component of the @vector by @factor. Note that
* this is equivalent to multiplying the vectors length by @factor.
**/
void
gimp_vector3_mul (GimpVector3 *vector,
gdouble factor)
{
vector->x *= factor;
vector->y *= factor;
vector->z *= factor;
}
/**
* gimp_vector3_mul_val:
* @vector: a #GimpVector3.
* @factor: a scalar.
*
* This function is identical to gimp_vector3_mul() but the vector is
* passed by value rather than by reference.
*
* Returns: the resulting #GimpVector3.
**/
GimpVector3
gimp_vector3_mul_val (GimpVector3 vector,
gdouble factor)
{
GimpVector3 result;
result.x = vector.x * factor;
result.y = vector.y * factor;
result.z = vector.z * factor;
return result;
}
/**
* gimp_vector3_normalize:
* @vector: a pointer to a #GimpVector3.
*
* Normalizes the @vector so the length of the @vector is 1.0. The nul
* vector will not be changed.
**/
void
gimp_vector3_normalize (GimpVector3 *vector)
{
gdouble len;
len = gimp_vector3_length (vector);
if (len != 0.0)
{
len = 1.0 / len;
vector->x *= len;
vector->y *= len;
vector->z *= len;
}
else
{
*vector = gimp_vector3_zero;
}
}
/**
* gimp_vector3_normalize_val:
* @vector: a #GimpVector3.
*
* This function is identical to gimp_vector3_normalize() but the
* vector is passed by value rather than by reference.
*
* Returns: a #GimpVector3 parallel to @vector, pointing in the same
* direction but with a length of 1.0.
**/
GimpVector3
gimp_vector3_normalize_val (GimpVector3 vector)
{
GimpVector3 result;
gdouble len;
len = gimp_vector3_length_val (vector);
if (len != 0.0)
{
len = 1.0 / len;
result.x = vector.x * len;
result.y = vector.y * len;
result.z = vector.z * len;
return result;
}
else
{
return gimp_vector3_zero;
}
}
/**
* gimp_vector3_neg:
* @vector: a pointer to a #GimpVector3.
*
* Negates the @vector (i.e. negate all its coordinates).
**/
void
gimp_vector3_neg (GimpVector3 *vector)
{
vector->x *= -1.0;
vector->y *= -1.0;
vector->z *= -1.0;
}
/**
* gimp_vector3_neg_val:
* @vector: a #GimpVector3.
*
* This function is identical to gimp_vector3_neg() but the vector
* is passed by value rather than by reference.
*
* Returns: the negated #GimpVector3.
**/
GimpVector3
gimp_vector3_neg_val (GimpVector3 vector)
{
GimpVector3 result;
result.x = vector.x * -1.0;
result.y = vector.y * -1.0;
result.z = vector.z * -1.0;
return result;
}
/**
* gimp_vector3_add:
* @result: destination for the resulting #GimpVector3.
* @vector1: a pointer to the first #GimpVector3.
* @vector2: a pointer to the second #GimpVector3.
*
* Computes the sum of two 3D vectors. The resulting #GimpVector3 is
* stored in @result.
**/
void
gimp_vector3_add (GimpVector3 *result,
const GimpVector3 *vector1,
const GimpVector3 *vector2)
{
result->x = vector1->x + vector2->x;
result->y = vector1->y + vector2->y;
result->z = vector1->z + vector2->z;
}
/**
* gimp_vector3_add_val:
* @vector1: a #GimpVector3.
* @vector2: a #GimpVector3.
*
* This function is identical to gimp_vector3_add() but the vectors
* are passed by value rather than by reference.
*
* Returns: the resulting #GimpVector3.
**/
GimpVector3
gimp_vector3_add_val (GimpVector3 vector1,
GimpVector3 vector2)
{
GimpVector3 result;
result.x = vector1.x + vector2.x;
result.y = vector1.y + vector2.y;
result.z = vector1.z + vector2.z;
return result;
}
/**
* gimp_vector3_sub:
* @result: the destination for the resulting #GimpVector3.
* @vector1: a pointer to the first #GimpVector3.
* @vector2: a pointer to the second #GimpVector3.
*
* Computes the difference of two 3D vectors (@vector1 minus @vector2).
* The resulting #GimpVector3 is stored in @result.
**/
void
gimp_vector3_sub (GimpVector3 *result,
const GimpVector3 *vector1,
const GimpVector3 *vector2)
{
result->x = vector1->x - vector2->x;
result->y = vector1->y - vector2->y;
result->z = vector1->z - vector2->z;
}
/**
* gimp_vector3_sub_val:
* @vector1: a #GimpVector3.
* @vector2: a #GimpVector3.
*
* This function is identical to gimp_vector3_sub() but the vectors
* are passed by value rather than by reference.
*
* Returns: the resulting #GimpVector3.
**/
GimpVector3
gimp_vector3_sub_val (GimpVector3 vector1,
GimpVector3 vector2)
{
GimpVector3 result;
result.x = vector1.x - vector2.x;
result.y = vector1.y - vector2.y;
result.z = vector1.z - vector2.z;
return result;
}
/**
* gimp_vector3_inner_product:
* @vector1: a pointer to the first #GimpVector3.
* @vector2: a pointer to the second #GimpVector3.
*
* Computes the inner (dot) product of two 3D vectors. This product
* is zero if and only if the two vectors are orthognal.
*
* Returns: The inner product.
**/
gdouble
gimp_vector3_inner_product (const GimpVector3 *vector1,
const GimpVector3 *vector2)
{
return (vector1->x * vector2->x +
vector1->y * vector2->y +
vector1->z * vector2->z);
}
/**
* gimp_vector3_inner_product_val:
* @vector1: the first #GimpVector3.
* @vector2: the second #GimpVector3.
*
* This function is identical to gimp_vector3_inner_product() but the
* vectors are passed by value rather than by reference.
*
* Returns: The inner product.
**/
gdouble
gimp_vector3_inner_product_val (GimpVector3 vector1,
GimpVector3 vector2)
{
return (vector1.x * vector2.x +
vector1.y * vector2.y +
vector1.z * vector2.z);
}
/**
* gimp_vector3_cross_product:
* @vector1: a pointer to the first #GimpVector3.
* @vector2: a pointer to the second #GimpVector3.
*
* Compute the cross product of two vectors. The result is a
* #GimpVector3 which is orthognal to both @vector1 and @vector2. If
* @vector1 and @vector2 and parallel, the result will be the nul
* vector.
*
* This function can be used to compute the normal of the plane
* defined by @vector1 and @vector2.
*
* Returns: The cross product.
**/
GimpVector3
gimp_vector3_cross_product (const GimpVector3 *vector1,
const GimpVector3 *vector2)
{
GimpVector3 normal;
normal.x = vector1->y * vector2->z - vector1->z * vector2->y;
normal.y = vector1->z * vector2->x - vector1->x * vector2->z;
normal.z = vector1->x * vector2->y - vector1->y * vector2->x;
return normal;
}
/**
* gimp_vector3_cross_product_val:
* @vector1: the first #GimpVector3.
* @vector2: the second #GimpVector3.
*
* This function is identical to gimp_vector3_cross_product() but the
* vectors are passed by value rather than by reference.
*
* Returns: The cross product.
**/
GimpVector3
gimp_vector3_cross_product_val (GimpVector3 vector1,
GimpVector3 vector2)
{
GimpVector3 normal;
normal.x = vector1.y * vector2.z - vector1.z * vector2.y;
normal.y = vector1.z * vector2.x - vector1.x * vector2.z;
normal.z = vector1.x * vector2.y - vector1.y * vector2.x;
return normal;
}
/**
* gimp_vector3_rotate:
* @vector: a pointer to a #GimpVector3.
* @alpha: the angle (in radian) of rotation around the Z axis.
* @beta: the angle (in radian) of rotation around the Y axis.
* @gamma: the angle (in radian) of rotation around the X axis.
*
* Rotates the @vector around the three axis (Z, Y, and X) by @alpha,
* @beta and @gamma, respectively.
*
* Note that the order of the rotation is very important. If you
* expect a vector to be rotated around X, and then around Y, you will
* have to call this function twice. Also, it is often wise to call
* this function with only one of @alpha, @beta and @gamma non-zero.
**/
void
gimp_vector3_rotate (GimpVector3 *vector,
gdouble alpha,
gdouble beta,
gdouble gamma)
{
GimpVector3 s, t;
/* First we rotate it around the Z axis (XY plane).. */
/* ================================================= */
s.x = cos (alpha) * vector->x + sin (alpha) * vector->y;
s.y = cos (alpha) * vector->y - sin (alpha) * vector->x;
/* ..then around the Y axis (XZ plane).. */
/* ===================================== */
t = s;
vector->x = cos (beta) *t.x + sin (beta) * vector->z;
s.z = cos (beta) *vector->z - sin (beta) * t.x;
/* ..and at last around the X axis (YZ plane) */
/* ========================================== */
vector->y = cos (gamma) * t.y + sin (gamma) * s.z;
vector->z = cos (gamma) * s.z - sin (gamma) * t.y;
}
/**
* gimp_vector3_rotate_val:
* @vector: a #GimpVector3.
* @alpha: the angle (in radian) of rotation around the Z axis.
* @beta: the angle (in radian) of rotation around the Y axis.
* @gamma: the angle (in radian) of rotation around the X axis.
*
* This function is identical to gimp_vector3_rotate() but the vectors
* are passed by value rather than by reference.
*
* Returns: the rotated vector.
**/
GimpVector3
gimp_vector3_rotate_val (GimpVector3 vector,
gdouble alpha,
gdouble beta,
gdouble gamma)
{
GimpVector3 s, t, result;
/* First we rotate it around the Z axis (XY plane).. */
/* ================================================= */
s.x = cos (alpha) * vector.x + sin (alpha) * vector.y;
s.y = cos (alpha) * vector.y - sin (alpha) * vector.x;
/* ..then around the Y axis (XZ plane).. */
/* ===================================== */
t = s;
result.x = cos (beta) *t.x + sin (beta) * vector.z;
s.z = cos (beta) *vector.z - sin (beta) * t.x;
/* ..and at last around the X axis (YZ plane) */
/* ========================================== */
result.y = cos (gamma) * t.y + sin (gamma) * s.z;
result.z = cos (gamma) * s.z - sin (gamma) * t.y;
return result;
}
/**
* gimp_vector_2d_to_3d:
* @sx: the abscisse of the upper-left screen rectangle.
* @sy: the ordinate of the upper-left screen rectangle.
* @w: the width of the screen rectangle.
* @h: the height of the screen rectangle.
* @x: the abscisse of the point in the screen rectangle to map.
* @y: the ordinate of the point in the screen rectangle to map.
* @vp: the position of the observer.
* @p: the resulting point.
*
* \"Compute screen (sx, sy) - (sx + w, sy + h) to 3D unit square
* mapping. The plane to map to is given in the z field of p. The
* observer is located at position vp (vp->z != 0.0).\"
*
* In other words, this computes the projection of the point (@x, @y)
* to the plane z = @p->z (parallel to XY), from the @vp point of view
* through the screen (@sx, @sy)->(@sx + @w, @sy + @h)
**/
void
gimp_vector_2d_to_3d (gint sx,
gint sy,
gint w,
gint h,
gint x,
gint y,
const GimpVector3 *vp,
GimpVector3 *p)
{
gdouble t = 0.0;
if (vp->x != 0.0)
t = (p->z - vp->z) / vp->z;
if (t != 0.0)
{
p->x = vp->x + t * (vp->x - ((gdouble) (x - sx) / (gdouble) w));
p->y = vp->y + t * (vp->y - ((gdouble) (y - sy) / (gdouble) h));
}
else
{
p->x = (gdouble) (x - sx) / (gdouble) w;
p->y = (gdouble) (y - sy) / (gdouble) h;
}
}
/**
* gimp_vector_2d_to_3d_val:
* @sx: the abscisse of the upper-left screen rectangle.
* @sy: the ordinate of the upper-left screen rectangle.
* @w: the width of the screen rectangle.
* @h: the height of the screen rectangle.
* @x: the abscisse of the point in the screen rectangle to map.
* @y: the ordinate of the point in the screen rectangle to map.
* @vp: position of the observer.
* @p: the resulting point.
*
* This function is identical to gimp_vector_2d_to_3d() but the
* position of the @observer and the resulting point @p are passed by
* value rather than by reference.
*
* Returns: the computed #GimpVector3 point.
**/
GimpVector3
gimp_vector_2d_to_3d_val (gint sx,
gint sy,
gint w,
gint h,
gint x,
gint y,
GimpVector3 vp,
GimpVector3 p)
{
GimpVector3 result;
gdouble t = 0.0;
if (vp.x != 0.0)
t = (p.z - vp.z) / vp.z;
if (t != 0.0)
{
result.x = vp.x + t * (vp.x - ((gdouble) (x - sx) / (gdouble) w));
result.y = vp.y + t * (vp.y - ((gdouble) (y - sy) / (gdouble) h));
}
else
{
result.x = (gdouble) (x - sx) / (gdouble) w;
result.y = (gdouble) (y - sy) / (gdouble) h;
}
return result;
}
/**
* gimp_vector_3d_to_2d:
* @sx: the abscisse of the upper-left screen rectangle.
* @sy: the ordinate of the upper-left screen rectangle.
* @w: the width of the screen rectangle.
* @h: the height of the screen rectangle.
* @x: the abscisse of the point in the screen rectangle to map (return value).
* @y: the ordinate of the point in the screen rectangle to map (return value).
* @vp: position of the observer.
* @p: the 3D point to project to the plane.
*
* Convert the given 3D point to 2D (project it onto the viewing
* plane, (sx, sy, 0) - (sx + w, sy + h, 0). The input is assumed to
* be in the unit square (0, 0, z) - (1, 1, z). The viewpoint of the
* observer is passed in vp.
*
* This is basically the opposite of gimp_vector_2d_to_3d().
**/
void
gimp_vector_3d_to_2d (gint sx,
gint sy,
gint w,
gint h,
gdouble *x,
gdouble *y,
const GimpVector3 *vp,
const GimpVector3 *p)
{
gdouble t;
GimpVector3 dir;
gimp_vector3_sub (&dir, p, vp);
gimp_vector3_normalize (&dir);
if (dir.z != 0.0)
{
t = (-1.0 * vp->z) / dir.z;
*x = (gdouble) sx + ((vp->x + t * dir.x) * (gdouble) w);
*y = (gdouble) sy + ((vp->y + t * dir.y) * (gdouble) h);
}
else
{
*x = (gdouble) sx + (p->x * (gdouble) w);
*y = (gdouble) sy + (p->y * (gdouble) h);
}
}