Is this GLSL equivalent to this HLSL?

Question

I was wondering if the both shader codes are equivalent. So the question is, is this GLSL

vNormal = mat3(FUSEE_ITMV[0].xyz, FUSEE_ITMV[1].xyz, FUSEE_ITMV[2].xyz) * fuNormal;

Equivalent to this HLSL?

float3x3 fMatrix = {FUSEE_ITMV[0].xyz,FUSEE_ITMV[1].xyz,FUSEE_ITMV[2].xyz};
output.normal = normalize(mul(input.normal,(float3x3)fMatrix));

Theoretical I'd say yes they are but I'm not sure. Can anyone verify that they are equivalent?

Answer 1

Yes, assuming your FUSEE_ITMV matrix in HLSL is the transpose of the FUSEE_ITMV GLSL matrix, otherwise you need to make sure it's transposed. GLSL mat3 deals with the passed vectors as columns of the matrix. HLSL float3x3 on the other hand deals with them as rows.

GLSL:

mat3 m( column0, column1, column2);
m[0]; // returs the first column

HLSL:

float3x3 m = float3x3(row0, row1, row2); // sets rows of matrix n
m[0]; // Returns first row.

As far as you are indexing you matrices in a uniform way, columns for columns and rows for rows, this will assign each column to its equivalent column in the glsl mat3 and each row to its equivalent row in the glsl float3x3