toMat4 is incorrect

[bengolds]

The current implementation of toMat4 is incorrect; I think maybe you're running into some gimbal lock or something? Here's a repro.

I implemented the following and it worked well.

toMat4 : Quaternion -> Mat4
toMat4 q =
    let
        ( x, y, z, w ) =
            ( getI q, getJ q, getK q, getScalar q )
    in
        Mat4.fromRecord
            { m11 = 1 - 2 * y * y - 2 * z * z
            , m12 = 2 * x * y - 2 * w * z
            , m13 = 2 * x * z + 2 * w * y
            , m14 = 0
            , m21 = 2 * x * y + 2 * w * z
            , m22 = 1 - 2 * x * x - 2 * z * z
            , m23 = 2 * y * z - 2 * w * x
            , m24 = 0
            , m31 = 2 * x * z - 2 * w * y
            , m32 = 2 * y * z + 2 * w * x
            , m33 = 1 - 2 * x * x - 2 * y * y
            , m34 = 0
            , m41 = 0
            , m42 = 0
            , m43 = 0
            , m44 = 1
            }

[Conrad Parker]

Hi,

sorry I missed the notification for this issue.

Thanks for the awesome repro and reference doc. I've applied this change and released version 2.0.1.