Converter generates incorrect rotation key frames

[pjcozzi]

Replaces KhronosGroup/glTF#244

---

A COLLADA model with the following animation (hand edited at this point) has five keyframes:

        <animation id="Geometry-mesh097_rotation098Z.ANGLE">
            <source id="Geometry-mesh097_rotation098Z.ANGLE-input">
                <float_array id="Geometry-mesh097_rotation098Z.ANGLE-input-array" count="5">0 0.5 1.0 1.5 2.0</float_array>
                <technique_common>
                    <accessor count="5" source="#Geometry-mesh097_rotation098Z.ANGLE-input-array" stride="1">
                        <param name="TIME" type="float" />
                    </accessor>
                </technique_common>
            </source>
            <source id="Geometry-mesh097_rotation098Z.ANGLE-output">
                <float_array id="Geometry-mesh097_rotation098Z.ANGLE-output-array" count="5">0 90 180 270 360</float_array>
                <technique_common>
                    <accessor count="5" source="#Geometry-mesh097_rotation098Z.ANGLE-output-array" stride="1">
                        <param name="ANGLE" type="float" />
                    </accessor>
                </technique_common>
            </source>
            <source id="Geometry-mesh097_rotation098Z.ANGLE-interpolations">
                <Name_array id="Geometry-mesh097_rotation098Z.ANGLE-interpolations-array" count="5">LINEAR LINEAR LINEAR LINEAR LINEAR</Name_array>
                <technique_common>
                    <accessor count="5" source="#Geometry-mesh097_rotation098Z.ANGLE-interpolations-array" stride="1">
                        <param name="INTERPOLATION" type="Name" />
                    </accessor>
                </technique_common>
            </source>
            <sampler id="Geometry-mesh097_rotation098Z.ANGLE-sampler">
                <input semantic="INPUT" source="#Geometry-mesh097_rotation098Z.ANGLE-input" />
                <input semantic="OUTPUT" source="#Geometry-mesh097_rotation098Z.ANGLE-output" />
                <input semantic="INTERPOLATION" source="#Geometry-mesh097_rotation098Z.ANGLE-interpolations" />
            </sampler>
            <channel source="#Geometry-mesh097_rotation098Z.ANGLE-sampler" target="Geometry-mesh097Node/rotation098Z.ANGLE" />
        </animation>

The rotation angles around Z are simply 0 90 180 270 360. However, the converter generates the following axis-angle rotations, which include an axis flip:

[1, 0, 0, 0]
[0, 0, 1, 1.5707963705062866]
[0, 0, 1, 3.1415927410125732]
[0, 0, -1, 1.5707963705062866]
[0, 0, -1, 0]

Adding more keyframes (with shorter deltas between the rotation angles) does not fix the problem nor does changing the domain from [0, 360] to [-180, 180].

[rck1]

I noticed the same issue. I am converting from Maya to COLLADA (using the OpenCollada plugin) and then using Collada2GLTF to convert the gltf. I get the axis flip issue on animations as well, i.e. rotations about the y-axis converts to rotations about the x-axis. Will there be a fix soon? Is there any work arounds in the meantime?

[lasalvavida]

@rck1, are you using the 2.0 branch?

[rck1]

@lasalvavida, I am using the pre-built binaries from the latest release (v2.0).

[lasalvavida]

@rck1, can you attach the model that isn't converting correctly here?

[rck1]

@lasalvavida, I won't be able to attach the model that I'm using at work but I'll see if I can replicate it at home.