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Screen move to model move?


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Does anyone know of a function or have a process of transforming a screen move to a 3D coordinate when not in a top view?


For catching moves in Update Support, I handle x and y moves differently than z moves.  So, for example, if looking at a front view, I want a y screen move to translate to a z object move.  The matrix reported in theData->fTransformOffset follows the screen coordinates.


I can easily catch the case I want:

if (!theData->fbIs3DMove && gSDK->GetProjection(gSDK->GetActiveLayer()) != projectionPlan )


But I can't seem to find an easy way to transform the screen offset to the model offset.

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You have probably already looked at this but in VS, there are functions to change coordinates:







Plus some others. I played with them MANY years ago, but don't really remember if I solved your problem or not.



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The SDK has equivalent functions. ScreenVecToModelVec looked promising, but it only works for two dimensional points, which limits its use to translating rotated plan. 


PlanarPtTo3DModelPt might work, but there would need to be a way to find the ID of the screen-aligned plane. 

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  • 2 weeks later...

OK, got it.  I can get the working plane and convert the working plane point to a model pt.


TransformMatrix matMove = theData->fTransformOffset;
WorldPt3 moveOffset = matMove.P();
bool isPlanarMove = false;
// Check if 2D move in 3D view
// If so, transform move vector so it acts with respect of the object
if (!theData->fbIs3DMove && gSDK->GetProjection(gSDK->GetActiveLayer()) != projectionPlan ) {
	TPlanarRefID wpRef = gSDK->GetWorkingPlanePlanarRefID();
	gSDK->PlanarPtTo3DModelPt(wpRef, WorldPt(matMove.P().x,matMove.P().y), moveOffset);
	isPlanarMove = true;


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