Assignment 08: Normal and Environment Maps

Requirements

• You will need to change your Mesh file format (both text and binary) to support tangents and bitangents
• You will need to update your vertex declaration to support both tangents and bitangents

Accept a tangent and a bitangent in model space as inputs to your vertex shader, and output them in world space to your fragment shader

• You can use the semantics TANGENT and BINORMAL
• Tangents and bitangents are transformed exactly the same way as normals, with the rotation only (because they are vectors and not points)

Add a new normal map texture to at least your standard diffuse lit and your diffuse and specular lit fragment shaders

• You may add normal maps to all of your lit fragment shaders if you wish
• You should probably create different vertex shaders for those that transform tangents and bitangents and pass them on, but this isn't required (Direct3D should still function correctly even if extra data is interpolated but not used)
• YOU STILL MUST HAVE A DIFFUSE TEXTURE
• This means that you will be setting two textures into your fragment shaders
• This also means that your Material will specify two image paths for both textures that the Effect expects

Calculate "normal mapping" in the fragment shader using the following algorithm:

• Normalize each of the three interpolated vectors: The normal, the tangent, and the bitangent
• Create a so-called "TBN" rotation matrix, which is a float3x3 with the tangent, then the bitangent, then the normal
• Note that this order is important. You can think of each of these as x, y, and z, respectively
• Sample the normal map to get a float3 representing how the normal should be modified. Since this came from a texture, each component will be in [0,1]
• Transform the sample from [0,1] to [-1,1]:
• float3 normal_texture = ( normalMapSample * 2.0 ) - 1.0;
• Transform the normal from normal space into world space using the TBN matrix:
• float3 normal_world = mul( normal_texture, rotation_textureToWorld );
• Now you can use the normal in world space just as you have in previous assignments to calculate lighting

Use the NVIDIA Photoshop Plugin to transform this height map into a normal map

• The CADE machines should have this plugin installed. If for any reason you don't think you have access to Photoshop and this plugin, let me know as early as possible. (If you let me know Friday afternoon I will not be sympathetic to your plight.)
• This plugin uses "height" maps as its source
• White is closer to the camera, black is further away
• Go to Filter->NVIDIA Tools->NormalMapFilter
• None of the "Invert" options should be selected
• You can increase "Scale" to emphasize the effect
• "Height Source" should be "Average RGB"
• A left-handed normal map should look like the red is coming from the right, and the green is coming from the bottom

At least one Entity in your scene should use the normal map you made from the height map. MAKE SURE THAT THE TEXT THAT SAYS RAISED LOOKS RAISED AND THE TEXT THAT SAYS SUNKEN LOOKS SUNKEN. This is a good way to verify that you are doing everything correctly.

You are encouraged to find or make other normal maps for your scene, but this isn't required (you can just use the one if you want). It is fun to see how using a normal map that matches the diffuse map enhances the quality of materials!

• If you find normal maps from other sources make sure that they match the left-handed red/green convention. Most normal maps you find will probably be right-handed and the green will look like it's coming from the top. You will have to invert the green channel in your image editing program of choice

Details

Exporting from Maya

• You can use the functions MFnMesh::getTangents() and MFnMesh::getBinormals() to get lists of tangents and bitangents
• You can use the function MItMeshPolygon::tangentIndex() to get the index for each vertex. Note that there is only one index that you should use for both tangents and bitangents (in other words, there is no binormalIndex() function)

Normal Mapping

• We are glossing over a lot of important details in this assignment. If you find that you can't get your normal mapping to look correct please email the mailing list so we can figure things out. We made need to do a few things in a more sophisticated manner if we run into problems that I haven't anticipated