Make sure you can run shadertest1.py and that you can see a filled green disk on the screen. The color green is being passed into the shader through the tint constant. Try different color values for this constant. Then open up shader1.sha and notice how the value is used in the vertex shader to assign a color to a vertex. Play with the color values inside the vertex shader and see how it affects the final render.

Open and run shadertest2.py and make sure that you can see a shaded sphere this time. Ambient, diffuse and specular colors are being passed to the shader as constants. You can play with these values. Also notice that the light node is passed to the shader as well. Open up shader2.sha and examine how these values are being used. The constant mpos_light is the model space position of the light that is being passed in. This position is used to calculate the Light Vector which is then used to find the angle between the surface and the light, which gives rise to a diffuse color attenuation value. The specular attenuation value is missing. Just like you needed the light position passed in to calculate the Light Vector, you'll need to pass in the camera position to calculate the View Vector, which will be needed to find the specular attenuation value. Once you've gotten the View Vector, you need to calculate the Light Reflection Vector with this formula: R=norm(2N(N.L)-L) and then you can calculate the specular attenuation value as the dot product of R and V raised to some power like 6 (pow(x,y) raises x to the power of y). Try to make this specular lighting work in your shader.

In your shadertest2.py, load shader3.sha instead of shader2.sha. This shader has moved the calculation of the diffuse color attenuation into the fragment shader by passing the Light Vector and the Normal Vector over there from the vertex shader. Finish adding the specular attenuation value to the light calculation in this shader using the fragment shader to calculate a per-pixel Light Reflection Vector. Once you get this working, notice the drastic difference in quality between the per-vertex specular lighting and the per-pixel specular lighting.

Let's add a texture to your sphere. Add the following lines to your python code (after you load the sphere model):

diffuse_map = loader.loadTexture("./Models/Textures/bricks.tga")
ts0 = TextureStage( 'level0' )
sphere.setTexture(ts0, diffuse_map)

You now have access to this texture inside your shader as the tex_0 color sampler. A texture is nothing but a lookup table for color values. Now multiply your out color (that already includes your light calculations) in the fragment shader with the color value found in tex_0 at the texture coordinates that are passed into the fragment shader in l_texcoord0. The lookup function is tex2D(texture, texturecoordinates). You should now see a nicely textured and shaded sphere.