Hello, this is my first post, and i am here to explain how to create and modifie work in 3D. Mainly in XSI at the moment, but i have plans to expand into Maya and Zbrush along the lines. For my first tutorial i will show you all how to make glass in XSI.
The following turtorial is for XSI v4.11 and higher
Glass may be hard to create in xsi, if you don't know what your doing. It is quite simple once you understand the basics of surface types and the render tree. You can start off by making whatever shape you would like to have the appearance of glass, i will be making a glass for the easy convenience of it. For material i suggest you use a blinn for its advanced control of the specular. You will want to give the glass a slight bluish tint, the natural color of glass, but if you prefer a different shade that is fine. I have put up a checker board floor and marble background to help show off the glass in some of the later steps.
The next problem you'll run into is how to make the surface look like glass. If you lower the Transparency you get something ghost like. If you increase the reflectivity of the Glass, you get something that seems to be made of highly polished chrome. When you combine both reflection and transparency you get something that neither looks ghost like, or chrome like, you get something that looks just wrong. 
What you want to do is to find the incidence. It is in the render tree under nodes/illumination/incidence. What the incidence does is work with the normals of an object and the camera. Some of the normals point towards the camera, and some face away, the valuable thing is that we can change the textures of the normals based on were they are in perspective of the camera. because glass is both reflective and transparent, but because a glass is more reflective on the sides, and transparent to a higher degree on the surface closer to you. To view the normals on an object go to display/attributes/normals, now any object you select will show normals on the surface of itself.
We want to create 2 incidences, one for the reflectivity and the other for the transparency. We want to plug the first incidence into the transparency of the material. We want the bias to be high and the gain to be low on this incidence. The bias controls the contrast between dark and light areas of shading. Values below 0.5 create larger dark areas, values above 0.5 create larger light areas. The gain controls the brightness of the effect. The relativity of this is that we can make the dark areas have a certain appearance, and the light areas have a different appearance. Since the dark will be transparent, as well as facing us we want a large area.
After we have finished that we can plug the second incidence into the reflectivity of the material. We also want a high bias and a low gain for the reflectivity, the difference is this time we will check a little box to invert it. Now you can see that our object is starting to look like glass, if not then its at least better then a polished ghost. But since the glass is still dark it doesn't look quite reall enough, thats easy enough to fix, all we have to do is go to the render options. In render options you can find a tap labeled 'optimize', under the tab there are several sliders, the ones were interested in right now are called Reflection, Refraction and Combined. reflections refers to how many times an image will be reflected, refraction is how many times you can view see through an object, and combined is the total of both. because we are looking through 4 layers on this glass, we must set the refraction to a minimum of 4. It is also very important that the combined slider is at least equal to the reflection and the refraction added together, if not you will encounter problems further along the way.
Now were getting close to the finished result of our actual glass. if the glass doesn't come out exactly the way youd like it to, dont get discouraged, most of the times you will need to adjust the sliders to change the glass. The next thing we need to do is to add the index of refraction to the glass, because when you look through an object the images on the other side are often distorted. The index is natural set to 1, we can move the slider up slowly, if you go too high the images on the back will be too distorted, if you dont go farth enough it wont appear to be distorted at all. Now we should have a glass that actualy looks like a glass, and not its freakish counter parts.
That is how we make glass! If you have any other problems, or would like to suggest a future topic please do not hesitate to email me at
nik.chauvin@gmail.com.
Or if you would like to purchase some premade 3D models, or comission work
No comments:
Post a Comment