topic Re: How to triangulate arcs in Archicad C++ API

How to triangulate arcs

Anonymous — Wed, 12 Jul 2023 19:02:35 GMT

Hello,

I'm new to Archicad and am looking into a bug whereby shell objects doesn't appear ( I suspect because there isn't an implementation to handle arcs/shell). The original implementer of our archicad codebase left so I'm picking up the pieces so to say.

From what I can tell, we are using ACPI_Goodies(API_RegularizePolyID) to triangulate Archicad primitives. I did fix the case for APIERR_IRREGULARPOLY by using API_RegularizedPolyID. However I'm still seeing error APIERR_REFUSEDPAR return by APIAny_TriangulatePolyID due to arc since the function only accept polygons w/o arc segments. I was just wondering if someone could point me towards tutorial/sample codes/ or how to go about triangulating arcs?

Thanks in advance,
Ian

Re: How to triangulate arcs

Akos Somorjai — Wed, 14 Dec 2016 08:10:44 GMT

IanTr wrote:
Hello,

I'm new to Archicad and am looking into a bug whereby shell objects doesn't appear ( I suspect because there isn't an implementation to handle arcs/shell). The original implementer of our archicad codebase left so I'm picking up the pieces so to say.

From what I can tell, we are using ACPI_Goodies(API_RegularizePolyID) to triangulate Archicad primitives. I did fix the case for APIERR_IRREGULARPOLY by using API_RegularizedPolyID. However I'm still seeing error APIERR_REFUSEDPAR return by APIAny_TriangulatePolyID due to arc since the function only accept polygons w/o arc segments. I was just wondering if someone could point me towards tutorial/sample codes/ or how to go about triangulating arcs?

Thanks in advance,
Ian

Hello Ian,

I would take a look at ACAPI_Goodies (APIAny_TriangulatePolyID, ...).

Best, Akos

Re: How to triangulate arcs

Anonymous — Wed, 14 Dec 2016 19:56:45 GMT

Akos,

According to the API doc, ACAPI_Goodies (APIAny_TriangulatePolyID, ...) only accept polygons that has no arc segments. The code snippet on that page also shows it skips over nArcs > 0. I was just wondering if there are functions/methods that I missed looking through the samples that handles triangulation of arcs.

Cheers,
Ian

Re: How to triangulate arcs

Ralph Wessel — Thu, 15 Dec 2016 10:51:47 GMT

IanTr wrote:
According to the API doc, ACAPI_Goodies (APIAny_TriangulatePolyID, ...) only accept polygons that has no arc segments. The code snippet on that page also shows it skips over nArcs > 0. I was just wondering if there are functions/methods that I missed looking through the samples that handles triangulation of arcs.

You could facet the arc edges to the required level of precision first.

Re: How to triangulate arcs

Akos Somorjai — Sun, 18 Dec 2016 10:40:49 GMT

Ralph wrote:
IanTr wrote:
According to the API doc, ACAPI_Goodies (APIAny_TriangulatePolyID, ...) only accept polygons that has no arc segments. The code snippet on that page also shows it skips over nArcs > 0. I was just wondering if there are functions/methods that I missed looking through the samples that handles triangulation of arcs.
You could facet the arc edges to the required level of precision first.

Ian,

Here comes a sample which shows how to do that with the help of the Geometry module.

#include "GenArc2DData.h"
#include "Ellipse2DData.h"

/*----------------------------------------------------------**
**	Gets the current ARCHICAD settings for arc division		**
**----------------------------------------------------------*/
static double GetMaxDiff ()
{
	double	maxDiff = EPS;
	if (ACAPI_Environment (APIEnv_GetExportToleranceID, &maxDiff) != NoError) {
		API_MagicWandInfo	mwi = {0};
		if (ACAPI_Environment (APIEnv_GetMagicWandSetsID, &mwi) != NoError)
			maxDiff = EPS;
		else
			maxDiff = mwi.arcDiff;
	}

	return maxDiff;
}

/*----------------------------------------------------------**
**	Divides an arc according to the currect AC settings		**
**----------------------------------------------------------*/
static GSErrCode DivideArc (const API_Coord& orig, double r,
							double begAng, double endAng, bool reflected,
							double ratio, bool elliptic,
							USize * nCo, Coord** hCo)
{
	GenArc genArc;

	if (elliptic) {
		genArc.SetToEllipseArc (Geometry::Ellipse ((const Coord &)orig, r, ratio, 0.0), begAng, endAng, reflected);
	} else {
		genArc.SetToCircleArc ((const Coord &)orig, r, begAng, endAng, reflected);
	}
	Geometry::DivideEllArcToCo  (genArc, GetMaxDiff (), hCo, nCo);

	return NoError;
}

/*----------------------------------------------------------**
**	Writes out a Circular/Elliptic Arc, divided				**
**----------------------------------------------------------*/
static GSErrCode	DWF_WrDividedArc (const API_Coord& orig, double r,
									  double begAng, double endAng, bool reflected = false,
									  double ratio = 1.0, bool elliptic = false)
{
	USize	nCo = 0;
	Coord	**hCo = reinterpret_cast<Coord **> (BMhAll (0));
	GSErrCode lastErr = DivideArc (orig, r, begAng, endAng, reflected, ratio, elliptic, &nCo, hCo);
	if (lastErr != NoError) {
		BMhFree ((GSHandle) hCo);
		return lastErr;
	}

	// ...

	BMhFree ((GSHandle) hCo);

	return lastErr;
}

Regards, Akos