OfxParametricParameterSuiteV1
— The OFX suite used to define and manipulate 'parametric' parameters.
#include "ofxParametricParam.h"
typedef struct OfxParametricParameterSuiteV1 {
OfxStatus (*parametricParamGetValue)(OfxParamHandle param,
int curveIndex,
OfxTime time,
double parametricPosition,
double *returnValue);
OfxStatus (*parametricParamGetNControlPoints)(OfxParamHandle param,
int curveIndex,
double time,
int *returnValue);
OfxStatus (*parametricParamGetNthControlPoint)(OfxParamHandle param,
int curveIndex,
double time,
int nthCtl,
double *key,
double *value);
OfxStatus (*parametricParamSetNthControlPoint)(OfxParamHandle param,
int curveIndex,
double time,
int nthCtl,
double key,
double value,
bool addAnimationKey);
OfxStatus (*parametricParamAddControlPoint)(OfxParamHandle param,
int curveIndex,
double time,
double key,
double value,
bool addAnimationKey);
OfxStatus (*parametricParamDeleteControlPoint)(OfxParamHandle param,
int curveIndex,
int nthCtl);
OfxStatus (*parametricParamDeleteAllControlPoints)(OfxParamHandle param,
int curveIndex);
} OfxParametricParameterSuiteV1;
This is an optional suite.
Parametric parameters are in effect 'functions' a plug-in can ask a host to arbitrarily evaluate for some value 'x'. A classic use case would be for constructing look-up tables, a plug-in would ask the host to evaluate one at multiple values from 0 to 1 and use that to fill an array.
A host would probably represent this to a user as a cubic curve in a standard curve editor interface, or possibly through scripting. The user would then use this to define the 'shape' of the parameter.
The evaluation of such params is not the same as animation, they are returning values based on some arbitrary argument orthogonal to time, so to evaluate such a param, you need to pass a parametric position and time.
Often, you would want such a parametric parameter to be multi-dimensional, for example, a colour look-up table might want three values, one for red, green and blue. Rather than declare three separate parametric parameters, it would be better to have one such parameter with multiple values in it.
The major complication with these parameters is how to allow a plug-in to set values, and defaults. The default default value of a parametric curve is to be an identity lookup. If a plugin wishes to set a different default value for a curve, it can use the suite to set key/value pairs on the m descriptor of the param. When a new instance is made, it will have these curve values as a default.