GA 3311: Materials and Lighting In this class students will be introduced to materials, textures and lighting strategies to add detail and realism to objects without adding complexity to the model. Students will simulate real world surfaces containing reflection radiosity and other effects. |
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Baking shadows and reflections to file-If our objects aren't moving in our scene, we can bake these effect right into the texture file.Click on the links below for a step by step. Note how in the fourth image that our baking becomes distorted when viewed from a different camera angle.Baking 3d or 2d procedural textures to file-
A Brownian 3d texture that has been baked to the UV set of an automatically mapped cube. We can bake a file texture by selecting the UV mapped surface and the material node. In the Hypershade, choose: Edit Convert to File Texture: Maya Software, and set your image size and file type.
Baking High Res Information to Low Res Models: TRANSFER MAPS-
We can also bake attributes of higher polycount models right into low poly models to speed up the time it takes to render. The general concept is that We can use pixels to store information about polygons, and that pixels take less time to render. To do these types of maps requires several specific things.
Displacemet Mapping :
This type of mapping (as explained in week 2), can effect the profile of an object, displacing the mesh to look like a higher poly mesh. We can use the Transfer maps function in maya to create this. Of note, is that Displacement mapping or Traditional Bump Mapping (which does not effect the alpha) are both types of height maps, and cannot be used in realtime situations. Thus, Enter the Normal Map--->Normal Mapping:
Bump Maps versus Normal Maps:
One of the major differences between Bump and Normal maps is they way that space is handled. With a Bump map, as we are all very well familiar with so far, height and depth are determined as a greyscale value with white being high and black being low. Of course, implicit in this formulation is the understanding that height and depth are thusly RELATIVE to each other. For light grey to be high, it has to be higher than dark grey. Without a darker grey area to define how much lower the lowest area should be than the highest areas, we are unable to determine our bumping effect.
Normal Maps work entirely different. Since a specific color value is used to determine the direction which a surface normal is
preterbed, there is no relative effect at play. Thusly Normal Maps are ABSOLUTE in value. Each RGB color points to XYZ space and that value is accurate without having to process their relativity scaling through an external node, which is why they can be processed by Hardware (and thusly are perfect for gaming applications).
Tangent Space Normals versus Object Space Normals versus World Space Normals:
There are three ways to define Normals space, off the Tangent, off the Object, and in relation to the World. To Render Normals in Maya we will need to calculate our maps using the Tangent Space Normals (TSN) configuration. TSNs will calculate the RGB values based on the original direction that each face's normal points. OSNs are calculated based on the the direction the object is positioned in XYZ space. WSNs calculate the vector direction based on the position of the object in world coordinates. These Maps have different uses:
Tangent Space Normals-can work on characters and objects that deform since the vector direction is based on each face
Object Space Normals- can not work on objects that deform since the vector is created off of the pivot point for the object. But, they render faster than TSN, do not exhibit seam problems (which TSNs can), and can be used for non-deforiming moving objects.
World Space Normals- are computed off of the 0,0,0 coordinate of world space and thus can only be used on objects that do not move in any way.The Major Benefit of normal mapping is that we can create a type of difference map that actually renders in real time. Normal maps use a color value to indicate which vector an object is pointing in. For Tangent Space Normal maps, the RGB Color Value for no deflection (pointing straight up) is 127,127, 255, its HEX code is #8080ff.
We will look more at normal maps and creating them with the Transfer Maps attribute in the Tutorial Listed in the Homework section below.Cavity (or Ambient Occlusion, or Diffuse) Mapping :
When two objects are close to each other, less light reaches the areas between the two of them. We can render this physically in Maya as so:
Using the mib_amb_occlusion texture under the mental ray nodes in the hypershade, we can connect the texture to the color and ambient color channels. By adjusting some settings, we get a render where light is occluded out of these areas.
Take a look at this demonstration by artist Alex Munn which discusses how to bake these effects into a texture:
http://www.alexmunn.com/html/class_levels_shader
s.htmUSING CRAZYBUMP to GENERATE NORMAL MAPS, CLICK ON THE IMAGE BELOW:
Homework:
There are several components to the Homework
assignment for this week. You will Produce 3 renders
(one from each designated camera in the scene file provided) of the Treasure
Chest and Coins. The Renders Must exhibit the following qualities:
FOR
THE TREASURE CHEST:
-A Normal Map created from the Transfer Maps function
-A Color Map created in Photoshop off the UV snapshot and Normal Map info
-A Specular Map created by modifing the color map in Photoshop. Used to
indicated what is or isnt shiny.
FOR
THE COINS:
-Uv map one coin to maximize the 0 to 1 space with no overlapping
-Transfer the Uvs from the UV mapped coin to all the others.
-A Color Map, either drawn or created from photoreference in Photoshop
-A Normal Map, modified from a Bump Map, Created in Photoshop Using the
NVidia Filter for Normal Map Generation in Photoshop (plugin) or CrazyBump
Click
Here for a Full Tutorial on how to set this up step by step:
 Image by Jonathan Binnie |
 Image by Sean Currey |
 Image by Ravi Giriputra |
 Image by Nhathy Ngo |
 Image by Dana Adams |
 Image by Ravi Giriputra |
