D3DXSHEvalDirection
Microsoft DirectX 9.0 SDK Update (October 2004)

D3DXSHEvalDirection Function


Evaluates the spherical harmonic (SH) basis functions from an input direction vector.

Syntax

FLOAT *WINAPI D3DXSHEvalDirection(      

    FLOAT *pOut,     UINT Order,     const D3DXVECTOR3 *pDir );

Parameters

pOut
[out] Pointer to SH output coefficients. The evaluation generates Order2 coefficients. See Remarks.
Order
[in] Order of the SH evaluation. Must be in the range of D3DXSH_MINORDER to D3DXSH_MAXORDER, inclusive. The evaluation generates Order2 coefficients. The degree of the evaluation is Order - 1.
pDir
[in] (x, y, z) direction vector in which to evaluate the SH basis functions. Must be normalized. See Remarks.

Return Value

Pointer to SH output coefficients. See Remarks.

Remarks

Each coefficient of the basis function Ylm is stored at memory location l2 + m + l, where:

On the sphere with unit radius as shown, direction can be specified simply with theta, the angle about the z-axis in the right-handed direction, and phi, the angle from z.

The following equations show the relationship between Cartesian (x, y, z) and spherical (theta, phi) coordinates on the unit sphere. The angle theta varies over the range of 0 to 2 pi, while phi varies from 0 to pi.

Function Information

Headerd3dx9math.h
Import libraryd3dx9.lib
Minimum operating systems Windows 98

See Also

Precomputed Radiance Transfer


© 2004 Microsoft Corporation. All rights reserved.
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