TS_cosKernel.C

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/// @file TS_cosKernel.C
/// @brief Sample metaball kernel function
///
/// This file demonstrates how to add a custom metaball kernel function that
/// will show up in all the Kernel Function parameter menus.
///
/// Once this file is compiled, register this dso into a @c MetaKernels text
/// file that is found in your HOUDINI_PATH environment variable. For example:
/// - <tt>$HOME/Library/Preferences/houdini/X.Y/MetaKernels</tt> <b>(OSX)</b>
/// - <tt>$HOME/houdiniX.Y/MetaKernels</tt> <b>(other platforms)</b>
///
/// The @c MetaKernels file should contain a list of .so/.dll paths that are
/// located relative to the search paths in the HOUDINI_DSO_PATH environment
/// variable. For example:
/// @code
///     # MetaKernels : Kernel extension table
///     TS_MyKernel.so
/// @endcode
/// In this case, you should install the TS_MyKernel.so file into the @c dso
/// subdirectory under where @c MetaKernels is found.
///
#include <UT/UT_DSOVersion.h>
#include <TS/TS_Expression.h>

#include <TS/TS_KernelList.h>

static float
evalPosition(float t)
{
    // Since distance passed in is squared, we must take the root...
    t = SYSsqrt(t);
    return SYScos(t*M_PI)*.5 + .5;
}

static float
evalGradient(float t)
{
    t = SYSsqrt(t);
    return .5*SYSsin(t*M_PI);
}

static float
cosFunc(float t)
{
    if (t <= 0) return 1;
    if (t >= 1) return 0;
    return evalPosition(t);
}

static UT_Interval
cosFuncRange(const UT_Interval &t)
{
    if (t.max <= 0) return UT_Interval(1, 1);
    if (t.min >= 1) return UT_Interval(0, 0);

    float min = cosFunc(t.max);
    float max = cosFunc(t.min);
    return (min > max) ? UT_Interval(max, min) : UT_Interval(min, max);
}

static float
cosDFunc(float t)
{
    if (t <= 0) return 0;
    if (t >= 1) return 0;
    return evalGradient(t);
}

static UT_Interval
cosDFuncRange(const UT_Interval &t)
{
    if (t.max <= 0 || t.min >= 1) return UT_Interval(0, 0);
    float min = cosDFunc(t.min);
    float max = cosDFunc(t.max);
    return (min > max) ? UT_Interval(max, min) : UT_Interval(min, max);
}

/// The kernel table definition
static TS_MetaKernel cosKernel = {
    "cosine",           // Token
    "Half Cosine",      // Label
    cosFunc,
    cosFuncRange,
    cosDFunc,
    cosDFuncRange
};

/// Registration function which installs the kernel
void
newMetaKernel()
{
    TS_KernelList::getList()->addKernel(&cosKernel);
}