My final competition is based on A3 Ray Tracing for galaxy plane and some sphere planets with their own simple texture mapping.
First I set all the shading material pararmeters ka, kd, ks, km to 0 for all objects, but except the phong exponentials has their own specific value in src/creative.json. According to the phone exponentials, it can be clearly identified each planets and the galaxy plane. For each different object I applied corresponding textures repectively. Therefore I modified src/raycolor.cpp and add 3 files, src/rgba_to_rgb.cpp from A1, src/raycolor_shading.cpp and src/bp_color_shading.cpp.
I read each texture .png files for each objects with read_rgbs_from_png.h from A1 and then converted rgba to rgb for eah object with src/rgba_to_rgb.cpp from A1.
In src/raycolor.cpp, I set different rgb to each different objects based on their phong exponentials, and set with its own texture rgb. With the updated rgb, I did the raycolor shading with ambient shading one more time using src/raycolor_shading.cpp and src/bp_color_shading.cpp, which are similar to src/raycolor.cpp and src/blinn_phong_shading.cpp but without the texture phong exponential checking and it based on the update colour rgb.
The result ppm is final.ppm.