# rtcInterpolate.3embree3 - Man Page

### NAME

rtcInterpolate - interpolates vertex attributes

### SYNOPSIS

#include <embree3/rtcore.h> struct RTCInterpolateArguments { RTCGeometry geometry; unsigned int primID; float u; float v; enum RTCBufferType bufferType; unsigned int bufferSlot; float* P; float* dPdu; float* dPdv; float* ddPdudu; float* ddPdvdv; float* ddPdudv; unsigned int valueCount; }; void rtcInterpolate( const struct RTCInterpolateArguments* args );

### DESCRIPTION

The `rtcInterpolate`

function smoothly interpolates per-vertex data over the geometry. This interpolation is supported for triangle meshes, quad meshes, curve geometries, and subdivision geometries. Apart from interpolating the vertex attribute itself, it is also possible to get the first and second order derivatives of that value. This interpolation ignores displacements of subdivision surfaces and always interpolates the underlying base surface.

The `rtcInterpolate`

call gets passed a number of arguments inside a structure of type `RTCInterpolateArguments`

. For some geometry (`geometry`

parameter) this function smoothly interpolates the per-vertex data stored inside the specified geometry buffer (`bufferType`

and `bufferSlot`

parameters) to the u/v location (`u`

and `v`

parameters) of the primitive (`primID`

parameter). The number of floating point values to interpolate and store to the destination arrays can be specified using the `valueCount`

parameter. As interpolation buffer, one can specify vertex buffers (`RTC_BUFFER_TYPE_VERTEX`

) and vertex attribute buffers (`RTC_BUFFER_TYPE_VERTEX_ATTRIBUTE`

) as well.

The `rtcInterpolate`

call stores `valueCount`

number of interpolated floating point values to the memory location pointed to by `P`

. One can avoid storing the interpolated value by setting `P`

to `NULL`

.

The first order derivative of the interpolation by u and v are stored at the `dPdu`

and `dPdv`

memory locations. One can avoid storing first order derivatives by setting both `dPdu`

and `dPdv`

to `NULL`

.

The second order derivatives are stored at the `ddPdudu`

, `ddPdvdv`

, and `ddPdudv`

memory locations. One can avoid storing second order derivatives by setting these three pointers to `NULL`

.

To use `rtcInterpolate`

for a geometry, all changes to that geometry must be properly committed using `rtcCommitGeometry`

.

All input buffers and output arrays must be padded to 16 bytes, as the implementation uses 16-byte SSE instructions to read and write into these buffers.

See tutorial [Interpolation] for an example of using the `rtcInterpolate`

function.

### EXIT STATUS

For performance reasons this function does not do any error checks, thus will not set any error flags on failure.

### SEE ALSO

[rtcInterpolateN]