Week 15 - Planet Models and Sky Box

My last major update was some weeks ago, detailing the completion of text on the screen. This that point, the program has progressing significantly - most of all aesthetically.

The first problem in the programs looks I wanted to solve was how to get a starry background in place - this adds greatly to the realism of the program. I decided that the best method would be to create a sky box - essentially a large box around the camera with edges that blend into each other, so it looks like a continuous background every way you look.

This proved to be more difficult that I had anticipated. In the end, I used sky box tutorial code, found here, and edited the size of the box and the images to be displayed myself. Another problem risen by this was the use of the GLaux library - which has been discontinued. This is mainly used in the loading of the BMP image for each side of the box. I had to implement replacement code, which I found here.

Initially, I used a really hi res star map I found using google images - this can be seen in the background for the program two blogs ago, showing the Earth. I replaced this with a star map found on the NASA website - namely, the Hipparcos star map. The stars are really colourful, and I used the original colouring at first - but found it was too hard to spot some of the smaller planets like Mercury in the program, because they looked like one of the stars in the map! So I greyscaled the image and used that as my background. Because the scene has to look continuous, every side of the sky box uses the same image.

In my project plan I had specified that I had hoped for planet modelling and loading into the program to be completed by this week, week 15 - and that is the other main part I have managed to complete this week. You can see the renders for each model in the previous blog. The models unfortunately cannot look that good in the program, but I think they still look pretty nice. Another big change from the previous blog is that I have fixed the lighting - in my excitement at getting the models into the program and working, I had not noticed that the lightning was no longer affecting them. In fact, I had forgot to turn on GL lightning in the myDrawGLScene class! I placed this call after the Sun model is draw - this way, shadows don't affect the Sun model so it appears to be a light source.

The final change I made was to make the model scales more realistic - previously, they were very rough estimates by myself, just to give an idea. I used the size calculator at this website, with the largest planet having a scale value of 1.21 - Jupiter (actually saturns is larger, but this is because the model is loaded in a lot smaller due to the rings). If the Sun was draw to scale, it would have a value of 11 - this is too large realistically for my model, so it is currently at a value of 2 (although I may change this).

Finally for this week, a screenshot of the program, again seen from Jupiter. As you can see, the lighting has made quite a difference to the quality of the model:

The inner four planets have all taken a size decrease, whilst Jupiter has actually got slightly bigger than I orginally had it. You can make out The Earth, Venus and Mercury in various states of orbit in the above image, as well as Mars (red dot some way above Venus, quite hard to spot!).

That's all for this week. The next major update will probably not be till the start of the new semester, due to exams.