How to Offset Dimensions Dynamically from Polyline Based on Annotation Scale

santhoshr151194 — Tue, 10 Jun 2025 15:44:51 GMT

I’m placing aligned dimensions along polyline segments using the AutoCAD .NET API. Right now, I position each dimension with a fixed perpendicular offset from the polyline, which works fine at first.

However, I’ve made the dimensions annotative to keep the text readable across layout viewports with different scales. As a result, the dimension text grows larger in some viewports, and the fixed offset causes the text to overlap with the polyline.

I’m looking for a way to offset dimensions dynamically based on annotation scale, so the spacing adjusts automatically and keeps the text clear and readable in all viewports.

Any best practices for dimensioning polylines like this when annotation scales are involved?

Any guidance would be appreciated — thanks!

Re: How to Offset Dimensions Dynamically from Polyline Based on Annotation Scale

fieldguy — Wed, 11 Jun 2025 21:03:49 GMT

See if this helps. You can obtain the "Current" annoscale with this.

// check the TextStyleTableRecord for annotative

acdb.TextStyleTableRecord tstr = (acdb.TextStyleTableRecord)tr.GetObject(mystyleid, acdb.OpenMode.ForRead);

double tsize = tstr.TextSize;

if (tsize == 0.0)

tsize = 2;

bool annotative = false;

if (tstr.Annotative == acdb.AnnotativeStates.True)

annotative = true;

double tsize = tstr.TextSize;

if (tsize == 0.0)

tsize = 2;

if (annotative)

{

acdb.ObjectContextManager ocm = db.ObjectContextManager;

acdb.ObjectContextCollection occ = ocm.GetContextCollection("ACDB_ANNOTATIONSCALES");

acdb.AnnotationScale asc = (acdb.AnnotationScale)occ.CurrentContext;

double psunits = asc.PaperUnits;

double msunits = asc.DrawingUnits;

double annofactor = 1;

if (asc.Name != "Model")

annofactor = msunits / psunits;

tsize = msunits / psunits * 2;

}// change size if annotative textstyle

I use a factor of 2 for calculating the insertion point later on. I create a new point3d by offsetting the midpoint of a line (or linesegment) using "annofactor".

topic How to Offset Dimensions Dynamically from Polyline Based on Annotation Scale in .NET Forum

How to Offset Dimensions Dynamically from Polyline Based on Annotation Scale

Re: How to Offset Dimensions Dynamically from Polyline Based on Annotation Scale