D3DXVEC2CATMULLLROM function
Perform CATMULL-ROM interpolation calculation. Here is 2-D vector interpolation.
definition:
D3DXVECTOR2 * WINAPI D3DXVEC2CATMULLROM
D3DXVECTOR2 * Pout,
Const d3dxvector2 * pv0,
Const d3dxvector2 * pv1,
Const d3dxvector2 * pv2,
Const d3dxvector2 * pv3,
Float S
);
parameter:
pout
[IN, OUT] points to the operation result of the D3DXVECTOR2 structure.
PV0
[in] points to the position vector of the D3DxVector2 structure.
PV1
[in] points to the position vector of the D3DxVector2 structure.
PV2
[in] points to the position vector of the D3DxVector2 structure.
PV3
[in] points to the position vector of the D3DxVector2 structure.
s
Weight factor. Review.
return value:
Point the CATMULL-ROM interpolation result of the D3DXVector2 structure.
Description:
If there are four points (P1, P2, P3, P4), find a function q (s) to satisfy the following conditions:
Q (s) is a three-function function equation.
When S ranges from 0 to 1, the Q (S) value is between P2 and P3.
When S is 0, Q (S) line is parallel to P1 and P3 straight lines.
When S is 1, Q (S) is straight in line parallel to the straight line of P2 and P4.
The CATMULL-ROM spline can also be obtained from the Hermite spline:
V1 = P2
V2 = P3
T1 = (p3 - p1) / 2
T2 = (p4 - p2) / 2
among them:
V1 is PV0.
V2 is PV1.
P3 is PV2.
P4 is PV3.
With Hermite formula:
Q (s) = (2S3 - 3S2 1) V1 (-2S3 3S2) V2 (S3 - 2S2 S) T1 (S3 - S2) T2
Switching with the above variable, the above formula is converted to:
Q (s) = (2S3 - 3S2 1) P2 (-2S3 3S2) P3 (S3 - 2S2 S) (P3 - P1) / 2 (S3 - S2) (P4 - P2) / 2
Retreating is:
Q (s) = [(-S3 2S2 - S) P1 (3S3 - 5S2 2) P2 (-3S3 4S2 S) P3 (S3 - S2) P4] / 2
Function information:
HEADER
D3DX9Math.h
Import Library
D3DX9.LIB
Minimum operation systems
WINDOWS 98
related functions:
D3DXVEC3CATMULLROM, D3DXVEC4CATMULLROM
