exp

Provides exponential 2^x with full precision to at least 1/2²⁰.

exp dest, src0

Registers

dest

Destination register.

src0

Input source register.

To learn more about registers, see Registers.

Remarks

float v = src0.w;
dest.x = dest.y = dest.z = dest.w = (float)pow(2, v);  

Example

// This example changes the value of the vertex color

// shader file
vs.1.0
m4x4 oPos, v0, c0	; transform vertices by view/projection matrix

mov r0, c5   		; load gray into register r0
mov r1, c4.y		; load 1's into register r1
exp r1.x, c6.y		; change r1.x only
        			; c6.y = 0.5 so r1.x = 20.5 = 1.4
mul r2, r0, r1		; scale r0 by r1

mov oD0,  r2		; output 

// The exp instruction causes the red component to increase about 40% 
// The resulting color is a dim red and is shown below

// Additional code is used to initialize the constant registers

D3DXMATRIX mat, matView, matProj;
D3DXMatrixMultiply(&mat, &matView, &matProj);
D3DXMatrixTranspose(&mat, &mat);
// set C0 with the view and projection matrix
m_pd3dDevice->SetVertexShaderConstant(0, &mat, 4);

// set register c4
float colorGreen[4] = {0, 1, 0, 0};
m_pd3dDevice->SetVertexShaderConstant(4, &colorGreen, 1);

// set register c5
float colorGray[] = {0.5f, 0.5f, 0.5f, 0.5f};
m_pd3dDevice->SetVertexShaderConstant(5, &gray, 1);

// set register c6
float exp[] = {0.24f, 0.48f, 0.96f, 1.92f};
m_pd3dDevice->SetVertexShaderConstant(6, &exp, 1);

// The first SetVertexShaderConstant method binds the C0 register 
// with the first row of the view/projection matrix (rows 2, 3, 4 are 
// bound to registers C2, C3, c4 also). The m4x4 instruction (in the 
// shader file) loads the data
// The second SetVertexShaderConstant method binds the C4 register 
// with the data for the color green. The next SetVertexShaderConstant 
// method binds the C5 register with the data for the color gray. The last 
// SetVertexShaderConstant method binds the C6 register with the data for 
// the exponent values.