Microsoft DirectX 8.1 (pixel shader versions 1.0, 1.1, 1.2, 1.3, 1.4)

lrp

Interpolates linearly between the second and third source registers by a proportion specified in the first source register.

lrp dest, src0, src1, src2

Registers

Argument	Description	Registers				Version
Argument	Description	v_n	c_n	t_n	r_n	Version
dest	Destination register				x	1.0
				x	x	1.1, 1.2, 1.3
					x	1.4
src0, src1, src2	Source register	x	x	x	x	1.0, 1.1, 1.2, 1.3
			x		x	1.4 phase 1
		x	x		x	1.4 phase 2

To learn more about registers, see Registers.

Remarks

This instruction performs the linear interpolation based on the following formula.

dest = src0 * src1 + (1-src0) * src2
// which is the same as
dest = src2 + src0 * (src1 - src2)

Example

This example is for illustration only. The C code accompanying the shader has not been optimized for performance.

// This example combines a texture color with a diffuse color value. // The shader is shown below. ps.1.0 // Version instruction. tex t0 // Declare texture. lrp r0, t0, v0, t0 // Blend from v0 to t0 by t0 amount. // The input colors and the output colors are shown below. The first image // (src0) determines the amount of the second image (src1) and the third image // (src2) that are blended to make the final image (dest). Where the first image // is white, the second image appears in the output. Where the first image is // black, the third images appears in the output. Where the first is gray, the // final image contains color values from the second and third image.

// Additional code loads the texture in texture stage 0. LPDIRECT3DDEVICE8 m_pd3dDevice; // initialize the pointer LPDIRECT3DTEXTURE8 m_pTexture0; // a pointer to the texture. TCHAR strPath[512] = "textureFile.jpg"; D3DUtil_CreateTexture( m_pd3dDevice, strPath, &m_pTexture0, D3DFMT_R5G6B5 ); m_pd3dDevice->SetTexture( 0, m_pTexture0 );