Unfortunately, the RenderTexture workflow in Unity is a bit limited and can only handle certain lighting setup. There are basically two ways:
1) Render the skeleton to the RenderTexture with an unlit shader,
and then render the RenderTexture quad to the screen with a lit shader.
2) Render the skeleton to the RenderTexture with a lit shader,
and then render the RenderTexture quad to the screen with an unlit shader.
Which of the two ways are you currently utilizing? In other words, which shaders are used at the skeleton, and which at the RenderTexture quad?
