Plane tangent and normal to surface?

MichaelPascoe

I'm trying to place a plane consistently on multiple types of faces to use in a transform. I can get a plane that is normal to the selected face, but I keep getting stuck.

The plane needs the following conditions:

• Origin: middle of selected curve/edge.
• Normal: same direction as curve/edge.
• X-axis: always facing toward the selected face not away from it.

Is there simple way to do this?

        var loopedEdges = qLoopEdges(definition.face);

        var evalLoopedEdges = evaluateQuery(context, loopedEdges);

        var normalPlane = evFaceTangentPlaneAtEdge(context, {
                "edge" : evalLoopedEdges[0],
                "face" : definition.face,
                "parameter" : .5,
                "usingFaceOrientation" : true
            });

My current attempts end up either not aligned with the chosen edge or facing away from the selected face.

NeilCooke

Use evEdgeTangentLine, then evFaceTangentPlane, then construct the plane from those results. 

konstantin_shiriazdanov

You can borrow this function:

/**
 * Returns normally oriented (by z axis) coord system in the closest point of reference surface.
 */
export function evRefCoordSys(context is Context, line is Line, referenceFaces is Query) returns CoordSystem
{
    var distanceResult = evDistance(context, {
            "side0" : referenceFaces,
            "side1" : line.origin
        });

    var faceNormal = evFaceTangentPlane(context, {
                "face" : referenceFaces->qNthElement(distanceResult.sides[0].index),
                "parameter" : distanceResult.sides[0].parameter
            }).normal;

    var dir = line.direction;
    dir = normalize(dir - dot(dir, faceNormal) * faceNormal);

    return coordSystem(line.origin, dir, faceNormal);
}

The trick is to perform Orthogonalization procedure of one of the vectors extracted from edge tangent and face normal to make sure those vectors are suiting for coordinate system definition. This is what does this string:

dir = normalize(dir - dot(dir, faceNormal) * faceNormal);

NeilCooke

Use evEdgeTangentLine, then evFaceTangentPlane, then construct the plane from those results. 

konstantin_shiriazdanov

You can borrow this function:

/**
 * Returns normally oriented (by z axis) coord system in the closest point of reference surface.
 */
export function evRefCoordSys(context is Context, line is Line, referenceFaces is Query) returns CoordSystem
{
    var distanceResult = evDistance(context, {
            "side0" : referenceFaces,
            "side1" : line.origin
        });

    var faceNormal = evFaceTangentPlane(context, {
                "face" : referenceFaces->qNthElement(distanceResult.sides[0].index),
                "parameter" : distanceResult.sides[0].parameter
            }).normal;

    var dir = line.direction;
    dir = normalize(dir - dot(dir, faceNormal) * faceNormal);

    return coordSystem(line.origin, dir, faceNormal);
}

The trick is to perform Orthogonalization procedure of one of the vectors extracted from edge tangent and face normal to make sure those vectors are suiting for coordinate system definition. This is what does this string:

dir = normalize(dir - dot(dir, faceNormal) * faceNormal);

Alex_Kempen

One solution that should work for placing planes on edges is to use evTangentLine to get a line tangent to the edge. You could then make a new plane with normal equal to the direction of the tangent line and with origin equal to the origin of the tangent line. In order to get the x-direction of the plane to run along the face, you could probably take the cross product of the direction of the line tangent to the edge and the normal of the face, which should give you a vector perpendicular to both.
In order to make the plane with all of your specifications, you may want to first make a coordsystem, then call plane(coordsystem) on that coordsystem. I hope that helps!

Alex_Kempen

Also, an easier way to get the edges adjacent to plane might be:

var edge = qAdjacent(definition.face, AdjacencyType.EDGE, EntityType.EDGE)->qNthElement(0);

This takes advantage of qNthElement to avoid having to evaluate the query first. 

MichaelPascoe

I posted this Friday night, woke up at 8am Saturday and already had two great responses! 

Thank you! @NeilCooke @konstantin_shiriazdanov @Alex_Kempen