# Synopsis

PDX_MSGT igeo_Convert144ToNurbs144(long option, MDA_PTR db_ptr, EAM_STACK *stack, int model, double tolerance, int max_iters, int u_degree, int v_degree, MDA_PTR *db_ptr_144, double *max_dev)

# Purpose

Convert an IGES 144 entity to an all IGES NURBS 144 entity

# Description

Given an IGES 144 entity that references non-NURBS entities, converts the non-NURBS entities to NURBS and converts all the 142 entities that reference non-NURBS IGES entities to reference IGES NURBS entities. If the IGES 144 and/or IGES 142 entities reference IGES NURBS entities, the NURBS entities are duplicated in the new model and the new IGES 144 and IGES 142 entities reference the duplicated IGES NURBS entities.

Parameter space curves are recomputed: .RS 4 o If the base surface was a non-NURBS surface that was converted to a NURBS (IGES 128) surfaces, .RE .RS 4 o The option mask equals IGEO_NEWPARMCRV, .RE .RS 4 o The paramter space curve for a given trimming curve (IGES 142) is missing (MDA_NULL_PTR), .RE .RS 4 o The original base curve for a given trimming curve (IGES 142) was not NURBS and the preference flag indicates that the model space curve definition is prefered. .RE

Model space curves are recomputed: .RS 4 o If the model space curves are non-NURBS, .RE .RS 4 o The option masks equals IGEO_NEWMODELCRV, .RE .RS 4 o The model space curve for a given trimming curve is missing (MDA_NULL_PTR) preference is not for the model space curve definition and the original base surface is an IGES NURBS surface and the parameter space curve is not missing. .RE

If the outer boundary of the 144 is the natural boundary of the surface and the option masks equals IGEO_NEWMODELCRV or IGEO_NEWPARMCRV, then both the model and parameter space curves are created as NURBS curves and a new outer 142 entity is created and the boundary type flag is changed to 1. The non-pointer DE parameter data of the surface is associated with the curve entities created in this case.

The u_degree and v_degree are used to determine the degree of an offset surface or offset curve ( u_degree ) that needs to be converted to an approximate NURBS curve or surface. If the option mask IGEO_USEUDEG is set then the u_degree is used to specify the degree of the parameter space curve created from projecting the NURBS model space curve to the NURBS surface (by default the degree of the existing parameter space curve or the maximium surface degree if the parameter space curve is missing is used for the degree of the parameter space curve). The tolerance and max_iters values apply to the NURBS curves or surface that are approximated. In addition, the tolerance applies to the test for curve and surface closure.

By default the IGES entity matrix is applied to the IGES NURBS curve and all the IGES 144 non-pointer DE attributes are applied to the new NURBS base IGES 144 entity. If the model is the same as the db_ptr model than all the IGES pointer DE attributes, property pointers and associativity pointers are applied to the new IGES NURBS base 144 entity.

The IGES 144 entity and all its subordinate entities must be valid IGES definitions except for the cases where missing model or parameter space curves are supported.

The conversion is exact where the curve and surface entities convert extactly to the NURBS definition, otherwise the conversion is an approximation to tolerance. The projection of new parameter space curves and/or creation of new model space curves from parameter space curves is an approximation to tolerance.

# Input

## option

### IGES_NOMATRIX

Do not apply entity matrix to data

### IGEO_KEEPRAT

Keep NURBS curves/surface rational when elevating the degree during conversion

### IGEO_BASEDEG

Use the base surface U and V degree for the degree of the offset surface

### IGEO_NEWPARMCRV

Recompute the parameter space trimming curve by projecting the NURBS model space curve to the NURBS surface in the cases where the base surface is already a NURBS surface

### IGEO_NEWMODELCRV

Recompute the NURBS model space trimming curve from the computed NURBS parameter space trimming curve. The curve preference flag will be set to parameter space curve prefered.

### IGEO_USEUDEG

Use the U degree parameter ( u_degree) for the degree of any new parameter space curves

### IGEO_OPENCLOSED

Open a closed surface if the projection of the model space curves generates multiple parameter space curves accross the seam closure. NOTE: If multiple parameter space curves still result, then the IGES 144 must be convert to an IGES 143

## db_ptr

The IGES 144 entity database pointer

## stack

The entity attribute stack handle

## model

The model to crete the new IGES 144 entity in

## tolerance

The conversion approximation tolerance. Note: The MODEL_SPACE_PNT_TOL should be at least 2 orders of magnitude less than this tolerance for correct results.

## max_iters

The maximium iterations for convergence test

## u_degree

The converted NURBS curve degree and/or the converted NURBS surface U degree (should be >= 1). See description for IGEO_USEUDEG option above.

## v_degree

The converted NURBS surface V degree (should be >= 1)

# Output

## db_ptr_144

The new IGES 144 entity database pointer

## max_dev

The maximium deviation of the model space curve to the surface.

# Tolerances

          MODEL_SPACE_PNT_TOL
          PARM_SPACE_PNT_TOL
          ANGLE_TOL
          ZERO_TOL
          CONVERGE_TOL
          KNOT_TOL
          PNT_PROJ_TOL
          PARALLEL_LINES_TOL
          .fi

# Return

          IGEO_NOERR
          IGEO_NOMEMORY
          Low level error return
          .fi