Platform SDK: DirectX |
Conditions are forces applied in response to current sensor values within the device. In other words, conditions require information about device motion, such as position or velocity of a joystick handle.
In general, conditions are not associated with individual events during a game or other application. They represent ambient phenomena, such as the stiffness or looseness of a flight stick, or the tendency of a steering wheel to return to a straight-ahead position.
A condition does not have a predefined magnitude; the magnitude is scaled in proportion to the movement or position of the input object.
DirectInput defines the following types of condition effects:
Most hardware devices do not support the application of envelopes to conditions.
Conditions have the following type-specific parameters:
Not all devices support saturation.
Not all devices support saturation.
Conditions can have duration, although in most cases, you would probably want to set the duration to infinite (–1) and stop the effect only in response to some event in the application.
To create a condition, pass one of the following values in the rguid parameter of the IDirectInputDevice7::CreateEffect method:
You can also pass any other GUID obtained by the IDirectInputDevice7::EnumEffects method, provided the low byte of the dwEffType member of the DIEFFECTINFO structure (DIEFT_GETTYPE(dwEfftype)) is equal to DIEFT_CONDITION. In this way, you can use hardware-specific conditions designed by the manufacturer.
The type-specific structure for conditions is DICONDITION. For multiple-axis conditions, you can provide an array of such structures, one for each axis, or a single structure that defines the condition in the specified direction. In either case, you must set the cbTypeSpecificParams member of the DIEFFECT structure to the number of bytes used; that is, to sizeof(DICONDITION) * n, where n is the number of structures provided. For more information on how to use either single or multiple structures, see the Remarks for the DICONDITION structure.
An application should call the IDirectInputDevice7::GetEffectInfo method or the IDirectInputDevice7::EnumEffects method and examine the dwEffectType member of the DIEFFECTINFO structure to determine whether both a positive and a negative coefficient and saturation for the effect are supported on the device. If the effect does not return the DIEFT_POSNEGCOEFFICIENTS flag, it ignores the value in the lNegativeCoefficient member, and the value in lPositiveCoefficient is applied to the entire axis. Likewise, if the effect does not return the DIEFT_POSNEGSATURATION flag, it ignores the value in dwNegativeSaturation, and the value in dwPositiveSaturation is used as the negative saturation level. Finally, if the effect does not return the DIEFT_SATURATION flag, it ignores both the dwPositiveSaturation and dwNegativeSaturation values, and no saturation is applied.
You can set a coefficient to a negative value, and this has the effect of generating the force in the opposite direction. For example, for a spring effect, it would cause the spring to push away from the offset point, rather than pulling toward it.
You should also check DIEFFECTINFO.dwEffectType for the DIEFT_DEADBAND flag, to see if deadband is supported for the condition. If it is not supported, the value in the lDeadBand member of the DICONDITION structure is ignored.
To create a condition, pass one of the following values in the rguid parameter of the IDirectInputDevice7::CreateEffect method:
You can also pass any other GUID obtained by the DirectInputEnumEffects.GetEffectGuid method, provided the low byte of the value returned by DirectInputEnumEffects.GetType is equal to DIEFT_CONDITION. In this way, you can use hardware-specific conditions designed by the manufacturer.
The type-specific parameters for a condition are described in a DICONDITION type in the condition member of the DIEFFECT type.
An application should call the DirectInputEnumEffects.GetType method and examine the return value member to determine whether both a positive and a negative coefficient and saturation for the effect are supported on the device. If the effect does not return the DIEFT_POSNEGCOEFFICIENTS flag, it ignores the value in DICONDITION.lNegativeCoefficient, and the value in lPositiveCoefficient is applied to the entire axis. Likewise, if the effect does not return the DIEFT_POSNEGSATURATION flag, it ignores the value in lNegativeSaturation, and the value in lPositiveSaturation is used as the negative saturation level. Finally, if the effect does not return the DIEFT_SATURATION flag, it ignores both the lPositiveSaturation and lNegativeSaturation values, and no saturation is applied.
You can set a coefficient to a negative value, and this has the effect of generating the force in the opposite direction. For example, for a spring effect, it would cause the spring to push away from the offset point, rather than pulling toward it.
You should also check the value returned by GetType for the DIEFT_DEADBAND flag, to see if deadband is supported for the condition. If it is not supported, the value in the lDeadBand member of the DICONDITION type is ignored.
To create a single-axis effect, set the coefficients for the unused axis to 0 in the conditionX or conditionY member of the DIEFFECT type.
DirectX for Visual Basic does not support rotation of conditions.