TransformControls: Use in-plane rotation when eye and selected gizmo axis are parallel #26860
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alankalb
changed the title
| _tempVector.cross( this.eye ); | ||
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| // When _tempVector is 0 after cross with this.eye the vectors are parallel and should use in-plane rotation logic. | ||
| if ( _tempVector.length() === 0 ) { |
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Shouldn't this be compared with an epsilon?
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By epsilon, do you mean a small threshold value? That could certainly help when the camera and axis are not strictly parallel but are practically parallel. When this happens the resulting cross product is normalized making a seemingly random vector that is used as the reference for rotation. If we we were to use an epsilon (assuming I am understanding it correctly) we would probably need to update the line this.rotationAxis.copy( this.eye ); in the in_plane rotation logic to be something like _inPlaneRotation ? this.rotationAxis.copy( _unit[ axis ] ) : this.rotationAxis.copy( this.eye ); to ensure you rotate around the intended axis rather than this.eye which may be very slightly off-axis.
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@LeviPesin Pinging you to get feedback on my previous response to your question.
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I'm not very sure, but I think using this.eye would be fine if it would be in any case within distance of epsilon from the axis?
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/ping @arodic |
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lgtm. Looking at the code this should work fine but please make sure there are no regressions. |
Description
I found this bug when using the rotate TransformControls in a web-app that allows users to set a camera to be perfectly parallel to a cardinal axis. When the TransformControls eye and the selected axis for rotation are parallel, the resulting rotation is zero as the cross product of two parallel vectors is the zero vector and the dot product with the zero vector is zero. This was fixed by performing the cross product and checking if the resulting vector has a length of zero, indicating that the vectors are parallel. If the vectors are parallel, the rotation logic for the
Ehandle is used.This bug does not occur very often as setting the value of
this.eyefrom the camera position usually small rounding errors causing the vector to not be perfectly parallel with a cardinal axis. For the app I am working on, the camera can be set perfectly inline with a cardinal axis when the rotation control is displayed causing the bug to occur frequently.Other notes/questions:
_inPlaneRotationis the best name for the variable. I tend to refer to theEhandle as the in-plane handle but I am open to other suggestions._tempVectoris equal to_zeroVectoras the resulting vector could include-0and may not be strictly equal to_zeroVectoreven when_tempVectorandthis.eyeare parallelBefore (using a modified version of the transform controls example where I have hardcoded the camera position to be parallel to the x-axis):
Screen.Recording.2023-09-27.at.4.52.49.PM.mov
After:
Screen.Recording.2023-09-27.at.4.53.17.PM.mov