confuse with row major and column major matrix multiplication in hlsl

Question

i realize that in d3dx math library or xnamath library, there matrix is saved row major in memory. in effect framework, when we set a matrix parameter by effect interface setvarible, it will transpose the target matrix. if i am not use effect framework, i must set shader parameter by SetVertexConstantF...

but when i use effect framework, i must transform vertices by this code:

OutPosition = mul( InPosition, mViewProj );

in normal shader code without effect framework, i must use:

OutPosition = mul( mViewProj, InPosition );

if i change the order of this , it will work incorrectly.

i found some article, they sait that hlsl store matrix as column major. if it is true, i think i must use pre-multiply matrix:

OutPosition = mul( mViewProj, InPosition );

but when i debug this in pix or nsight, i found that the marix parameter is store in register as it in the memory, for example: if mViewProj is:

x0 y0 z0 w0
x1 y1 z1 w1
x2 y2 z2 w2
x3 y3 z3 w3

in vertex shader register:

c0:x0 y0 z0 w0
c1:x1 y1 z1 w1
c2:x2 y2 z2 w2
c3:x3 y3 z3 w3

it looks like store as row major. why?

is this conflict with the basic rules of matrix multiplication: column major: matrix * vec row major : vec * matrix.

Ahmed Saleh Ahmed Saleh · Accepted Answer · 2014-11-18T15:38:55

HLSL uses Column-Major and XNAMath uses ROW-Major. Transpose your matrices before supplying it to the HLSL Shader should work. I was confused too two days ago.

confuse with row major and column major matrix multiplication in hlsl

1 Answers