HM_ExtAPI::SurfaceComposedGetPatch()

Syntax

bool SurfaceComposedGetPatch(
const HM_EntityGeometrySurface & surface,
int u_ind,
int v_ind,
HM_EntityGeometrySurface& patch,
double& u_start_param,
double& u_end_param,
double& v_start_param,
double& v_end_param,
double& patch_u_start_param,
double& patch_u_end_param,
double& patch_v_start_param,
double& patch_v_end_param
);

Type

HyperMesh Ext API Function

Description

The function expects that the type of surface object is HM_ExtAPI::COMPOSED_SURFACE. Application should call the function HM_ExtAPI::GeomSurfaceGetType() to verify the type before calling SurfaceComposedGetPatch function.

Use the function HM_ExtAPI::SurfaceComposedGetSizes() to get number of surface patches in U and V direction of the patches grid that defines the structure of the composed surface.

Composed surface geometry is defined by its patches. The parametric space of the composed surface is subdivided into the grid of rectangular cells with each cell corresponding to one of the patches of the composed surface. Depending on the location of the composed surface parameter in one of parametric cells corresponding patch is used to calculate the surface point for this parameter.

Subdivision of parametric space of the composed surface is defined by a set of grid parametric values for U parameter {uα} with index α taking the values in the range 0 … N and N is the number of patches in U parametric direction, and a set of grid parametric values for V parameter {vβ} with index β taking values in the range 0 … M and M is the number of patches in V parametric direction. For parametric values U and V such that

uα ≤ U ≤ uα+1 and vβ ≤ V ≤ vβ+1

the point on the composed surface is calculated as

S(U, V) = Sαβ(u, v)

where "local" patch parameters u and v are obtained by mapping from "global" parameters U and V using grid parametric values and patch parametric range values as

u = uαβ, 0 + (uαβ, 1 - uαβ, 0) (U - uα) / (uα+1 - uα)

v = vαβ, 0 + (vαβ, 1 - vαβ, 0) (V - vβ) / (vβ+1 - vβ)

The following table clarifies correspondence between parameters used in the equations above and parameter values returned by the function SurfaceComposedGetPatch.

Parameters returned by SurfaceComposedGetPatch	Composed surface parameters
u_ind	α
v_ind	β
patch	Sαβ
u_start_param	uα
u_end_param	uα+1
v_start_param	vβ
v_end_param	vβ+1
patch_u_start_param	uαβ, 0
patch_u_end_param	uαβ, 1
patch_v_start_param	vαβ, 0
patch_v_end_param	vαβ, 1

Parameters returned by SurfaceComposedGetSizes
u_cnt	N
v_cnt	M

If the function succeeds, the return value is true. If the function fails, the return value is false. To get extended value information, call HM_ExtAPI::GetLastErrorCode().

Requires including hm_extapi.h.

Inputs

surface: [in] - Handle to surface object that was returned by previous calls to API functions.
u_ind: [in] - Surface patch index in U parametric direction of surfaces grid. The value must be in the range from 0 to u_cnt - 1, where u_cnt is the size of the grid in U direction as returned by the function HM_ExtAPI::SurfaceComposedGetSizes().
v_ind: [in] - Surface patch index in V parametric direction of surfaces grid. The value must be in the range from 0 to v_cnt - 1, where v_cnt is the size of the grid in V direction as returned by the function HM_ExtAPI::SurfaceComposedGetSizes().
patch: [out] - Surface patch.
u_start_param: [in] - U parameter of composed surface that corresponds to start of U parametric range of active area of the patch, which in turn is defined by patch parameter patch_u_start_param.
u_end_param: [out] - U parameter of composed surface that corresponds to end of U parametric range of active area of the patch, which in turn is defined by patch parameter patch_u_end_param.
v_start_param: [in] - V parameter of composed surface that corresponds to start of V parametric range of active area of the patch, which in turn is defined by patch parameter patch_v_start_param.
v_end_param: [out] - V parameter of composed surface that corresponds to end of V parametric range of active area of the patch, which in turn is defined by patch parameter patch_v_end_param.
patch_u_start_param: [out] - Surface patch parameter that defines start of U parametric range of active area included into the composed surface.
patch_u_end_param: [out] - Surface patch parameter that defines end of U parametric range of active area included into the composed surface.
patch_v_start_param: [out] - Surface patch parameter that defines start of V parametric range of active area included into the composed surface.
patch_v_end_param: [out] - Surface patch parameter that defines end of V parametric range of active area included into the composed surface.

Errors

None.