NAME
SoCalculator -
General purpose calculator for floats and 3D float vectors.
The SoCalculator uses the values from the input fields (which are
either single floating point values or vectors) as variables in the
free-form engine expressions and places the results on the output
fields.
SYNOPSIS
#include <Inventor/engines/SoCalculator.h>
Inherits SoEngine.
Public Member Functions
SoCalculator (void)
Static Public Member Functions
static void initClass (void)
Public Attributes
SoMFFloat a
SoMFFloat b
SoMFFloat c
SoMFFloat d
SoMFFloat e
SoMFFloat f
SoMFFloat g
SoMFFloat h
SoMFVec3f A
SoMFVec3f B
SoMFVec3f C
SoMFVec3f D
SoMFVec3f E
SoMFVec3f F
SoMFVec3f G
SoMFVec3f H
SoMFString expression
SoEngineOutput oa
SoEngineOutput ob
SoEngineOutput oc
SoEngineOutput od
SoEngineOutput oA
SoEngineOutput oB
SoEngineOutput oC
SoEngineOutput oD
Protected Member Functions
virtual ~SoCalculator (void)
virtual void inputChanged (SoField *which)
Detailed Description
General purpose calculator for floats and 3D float vectors.
The SoCalculator uses the values from the input fields (which are
either single floating point values or vectors) as variables in the
free-form engine expressions and places the results on the output
fields.
The engine has sixteen input fields; eight scalar inputs (a, b, c, d,
e, f g, and h), and eight vector inputs (A, B, C, D, E, F, G, and H).
There are eight output fields; four scalar outputs (oa, ob, oc, and
od), and four vector outputs (oA, oB, oC, and oD).
The expression syntax is quite similar to C/C++, with a very limited
set of keywords and functions.
An example:
oa = a * (0.5 + b) / c
Will multiply the value in a with the value in b plus 0.5, divide that
result with c, and place the result in oa. Since this is an engine, the
expression will only be evaluated when someone attempts to read the
value in oa, not every time an input in changed.
All inputs are multi-fields, and if there are several values in an
input, the expression will be evaluated once for every input field
value, and the output will create as many values as there are input
field values.
If there is more than one input field, and the input fields do not have
the same number of values, the engine will create as many output values
as the input field with the biggest number of values. When the index
get out of bounds for some other input field, the last field value will
be used.
Vector expressions are similar to scalar expression. An example:
oA = A + vec3f(1.0, 0.0, 0.0) * B
Will take the vector in A, add the value in B multiplied with (1,0,0),
and place the result in oA.
In addition to regular arithmetics, the SoCalculator syntax also
includes some functions.
Scalar functions:
· cos(x) - cosine function (x in radians)
· sin(x) - sinus function
· tan(x) - tangent function
· acos(x) - arc cosine function
· asin(x) - arc sinus function
· atan(x) - arc tangent function
· atan2(y, x) - arc tangent function of two variables (y, x).
· cosh(x) - hyperbolic cosine function
· sinh(x) - hyperbolic sinus function
· tanh(x) - hyperbolic tangent function
· sqrt(x) - square root function
· pow(x,y) - x raised to the power of y
· exp(x) - e to the power of x
· log(x) - natural logarithm of x
· log10() - base-10 logarithm of x
· ceil(x) - rounds x upwards to the nearest integer
· floor(x) - rounds x downwards to the nearest integer
· fabs(x) - absolute value
· fmod(x, y) - remainder of dividing x by y
· rand(x) - pseudo-random value between 0 and 1
Vector functions:
· cross(x, y) - cross product of x and y
· dot(x,y) - dot product of x and y (returns scalar value)
· length(x) - length of x (returns scalar value)
· normalize(x) - returns normalized version of x
· x[y] - access components in x (y should be a scalar value in the
range [0,2])
There are also some named constants that can be used:
· MAXFLOAT
· MINFLOAT
· M_E
· M_LOG2E
· M_LOG10E
· M_LN2
· M_PI
· M_SQRT2 - sqrt(2)
· M_SQRT1_2 - sqrt(1/2)
The only control flow available is the ? operator. An example:
oa = (a > b) ? (a * 0.5) : (b * c)
(The parentheses are not necessary, they’re there just to make the
example easier to read)
In addition to the standard comparators (<, >, <=, >=, ==, !=), you can
also use && (AND) and || (OR) to combine expression, and the unary !
(NOT) operator.
One final thing worth mentioning is the temporary variables. There
exists sixteen temporary variables that can be used in expressions. ta,
tb, tc, td, te, tf, tg, and th are scalar variables, and tA, tB, tC,
tD, tE, tF, tG, and tH are vector variables. They are usually used when
you have more than one expression that should be evaluated in order.
An example with three expressions:
ta = a * b; tb = c + d; tc = e - f
tA = vec3f(ta, tb, tc) + A
oA = tA * B
The example just shows how temporary variables can be used to make your
expressions easier to read. Please note that it’s possible to have
several statements in one expression. You just separate them with
semicolons.
Here is a simple example of how an SoCalculator engine may be used in
an .iv file:
DEF mycamera PerspectiveCamera {
orientation 1 0 0 1.57
}
DEF headlight DirectionalLight {
intensity 0.8
direction 0 0 1
}
Separator {
# Render a cube not affected by lighting
LightModel { model BASE_COLOR }
BaseColor { rgb = Calculator {
a = USE headlight . intensity
expression [ ’oA = vec3f( a, a, a)’ ]
} . oA }
Cube {}
}
In the example, the color of the Cube is a function of the intensity of
the DirectionalLight, even though the Cube is rendered without lighting
because of the BASE_COLOR LightModel.
Constructor & Destructor Documentation
SoCalculator::SoCalculator (void) Constructor.
SoCalculator::~SoCalculator (void) [protected, virtual] Destructor.
Member Function Documentation
void SoCalculator::initClass (void) [static] Sets up initialization for
data common to all instances of this class, like submitting necessary
information to the Coin type system.
Reimplemented from SoEngine.
Member Data Documentation
SoMFFloat SoCalculator::a Input floating point value for the expressions.
SoMFFloat SoCalculator::b Input floating point value for the expressions.
SoMFFloat SoCalculator::c Input floating point value for the expressions.
SoMFFloat SoCalculator::d Input floating point value for the expressions.
SoMFFloat SoCalculator::e Input floating point value for the expressions.
SoMFFloat SoCalculator::f Input floating point value for the expressions.
SoMFFloat SoCalculator::g Input floating point value for the expressions.
SoMFFloat SoCalculator::h Input floating point value for the expressions.
SoMFVec3f SoCalculator::A Input vector with three floating point values for
the expressions.
SoMFVec3f SoCalculator::B Input vector with three floating point values for
the expressions.
SoMFVec3f SoCalculator::C Input vector with three floating point values for
the expressions.
SoMFVec3f SoCalculator::D Input vector with three floating point values for
the expressions.
SoMFVec3f SoCalculator::E Input vector with three floating point values for
the expressions.
SoMFVec3f SoCalculator::F Input vector with three floating point values for
the expressions.
SoMFVec3f SoCalculator::G Input vector with three floating point values for
the expressions.
SoMFVec3f SoCalculator::H Input vector with three floating point values for
the expressions.
SoMFString SoCalculator::expression Mathematical expressions for the
calculator.
SoEngineOutput SoCalculator::oa (SoMFFloat) Output value with result from
the calculations.
SoEngineOutput SoCalculator::ob (SoMFFloat) Output value with result from
the calculations.
SoEngineOutput SoCalculator::oc (SoMFFloat) Output value with result from
the calculations.
SoEngineOutput SoCalculator::od (SoMFFloat) Output value with result from
the calculations.
SoEngineOutput SoCalculator::oA (SoMFVec3f) Output value with result from
the calculations.
SoEngineOutput SoCalculator::oB (SoMFVec3f) Output value with result from
the calculations.
SoEngineOutput SoCalculator::oC (SoMFVec3f) Output value with result from
the calculations.
SoEngineOutput SoCalculator::oD (SoMFVec3f) Output value with result from
the calculations.
Author
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