Transform & CornerPin: live preview

[devernay]

We may implement live preview for transform nodes.

Live preview requires a lot more of opengl code, because the preview should not trigger a render (which may have motion blur, etc.). It's feasible, though (fetch the image and texture-map it with projective texture mapping).

Unfortunately there's officially no way to fetch an image from an OpenFX Interact:

Images may be fetched from an attached clip in the following situations...

• in the kOfxImageEffectActionRender action
• in the kOfxActionInstanceChanged and kOfxActionEndInstanceChanged actions with a kOfxPropChangeReason of kOfxChangeUserEdited
  http://openfx.sourceforge.net/Documentation/1.3/ofxProgrammingReference.html#ImageEffectsImagesAndClipsUsingClips

I think of two ways to get the texture:

• cache the last source image rendered with kOfxPropIsInteractive set to true, (or should we use kOfxImageEffectPropInteractiveRenderStatus ?) and use that as texture for the live preview
• trigger a kOfxActionInstanceChanged with kOfxChangeUserEdited, by setting a special value (a secret pushbutton maybe) when the button is pressed. But when we setValue from an interact, is it kOfxChangeUserEdited or kOfxChangePluginEdited, @MrKepzie?

Any help/advice on this issue is welcome.

See also MrKepzie/Natron#34

[MrKepzie]

We could simply do this when a parameter attached to the interact is changed by the user.

On Jul 5, 2014, at 6:53 PM, Frédéric Devernay [email protected] wrote:

We may implement live preview for transform nodes.

Live preview requires a lot more of opengl code, because the preview should not trigger a render (which may have motion blur, etc.). It's feasible, though (fetch the image and texture-map it with projective texture mapping).

Unfortunately there's officially no way to fetch an image from an OpenFX Interact:

Images may be fetched from an attached clip in the following situations...

in the kOfxImageEffectActionRender action
in the kOfxActionInstanceChanged and kOfxActionEndInstanceChanged actions with a kOfxPropChangeReason of kOfxChangeUserEdited http://openfx.sourceforge.net/Documentation/1.3/ofxProgrammingReference.html#ImageEffectsImagesAndClipsUsingClips
I think of two ways to get the texture:

cache the last source image rendered with kOfxPropIsInteractive set to true, (or should we use kOfxImageEffectPropInteractiveRenderStatus ?) and use that as texture for the live preview
trigger a kOfxActionInstanceChanged with kOfxChangeUserEdited, by setting a special value (a secret pushbutton maybe) when the button is pressed. But when we setValue from an interact, is it kOfxChangeUserEdited or kOfxChangePluginEdited, @MrKepzie?
See alse MrKepzie/Natron#34

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[devernay]

Sure, but the question was:
"when we setValue from an interact, is it kOfxChangeUserEdited or kOfxChangePluginEdited, @MrKepzie?"

when calling setValue from the plugin, it gives no option to say it is a user-edited change. I think Natron calls InstanceChanged with kOfxChangePluginEdited in all cases.

perhaps all setValue calls from an Interact should be considered as user-edited? Would that be possible? Can Natron distinguish wether setValue was called from an Interact action?

f