We are going to start by rendering our sphere in a solid color but with lighted shading. As usual, we start by writing the shader functions that, among other things, define the program variables they will need from the Material that uses it. Then, we'll define the SolidColorLightingMaterial class and add it to the Sphere component.
In the previous chapters, where we used shaders with lighting, we did the lighting calculations in the vertex shader. That's simpler (and faster), but transitioning the calculations to the fragment shader yields better results. The reason is that, in the vertex shader, you only have one normal value to compare against the light direction. In the fragment, all vertex attributes are interpolated, meaning that the normal value at a given point between two vertices will be some point in between their two normals. When this is the case, you see a smooth gradient across the triangle face, rather than localized...