You will be given the Blank_Treasure_Chest.ma file (in my week 8 folder) which will contain several items. First of all, it will have 3 lights, already set up for rendering, 3 cameras in addition to the perspective and orthos which you will be required to produce renders from each by the end, and several polygon objects. The first two objects that concern us are the High and Low Polygon count chests, which are on display layers for easy toggling. Also note that they over lap in 3d space even though here they are depicted side by side. As you see below, one chest is of considerably greater detail than the first. It is going to be our job to transfer this detail. How you might ask... with TRANSFER MAPS... thats how!
step 2:
Time to transfer our information. Make sure you are in the rendering window set in Maya, and under the Lighting/Shading menu, choose transfer maps:
step 3:
Select the lowpoly chest and click Add Selected for our Target Meshes section since we want to transfer our information to this model. Make sure to leave the Search Envelop at 0.0 so that Maya wraps its search area tightly around the model when creating the maps.
Now select the highpoly chest and click Add Selected for our Source Meshes section. This will now make this model the source of the information to be transfered.
Under the Connect Output Maps rollout, set it so the Maya will automatically Connect the new maps to the shader, and have it add those maps to the already assigned shader. (before doing the transfer, make sure that you have assigned your own material)
step 4:
Click on the Big 'ole Icon for Normal Map under the Output maps tab. Set the destination and name of the map in the first window, then it's file format in the second (targas will work very nicely). For the reasons explained on the last page, make sure that out Map space is set to Tangent space.
Under the Maya Common output, set the size of the map next. We will want to transfer our maps in Object Space not World Space as this will make sure that even if the meshes are not overlapping, the map will still transfer properly. DO NOT CONFUSE THIS WITH THE SPACE REQUIREMENTS FOR THE NORMAL MAP!
Set your sample quality, and when done, hit Bake (or Bake and Close).
This
will automatically attach the newly created normal map to a bump2d node which
has been set to be used as tangent space normals (not as bump). Note, this
option not available before Maya version 7.0. This map has then been attached
to the blinn's bump map section.
Here's
a look at my computed map (saved for web... do not use!). Note the color vectors
which show the direction based on each normal. If parts of your map show up
in error, remember that you can use the 128,128, 255 color (the periwinkle
that you see below) to re-normalize bad sections of your map.
step 5:
Perform a test render. This will reveal the dramatic change in your file (ignore the change in the coins below, were getting to those in a bit):
step 6:
Time to make a Color Map. To do this I have started out in Photoshop with my Uv snapshot as a guide. You can also use your normal map as a guide to reveal where cracks are, as well as the placement of the locks. I have used several photosamples, keeping in mind the direction that the grain of wood must flow to look correct. Examine below how since I have rotated my UVs for the top of the chest to place them best into the 0,1 space, I have also rotated my textures.
Another trick I have used is blurring out an inverted version of my UV snapshot (we looked at this in class) to darken up my corners. You can see evidence of the grid lines in my color texuture as a result.
Finally, I have also made sure to come back in at the end and paint over the wood with a tan colored brushstroke to randomize aging and scuffing into the texture. Doing this can add great life to a texture file, even as simple as my demo is.
step
7:
I also want to create a map for my specular color section in my blinn. This map will tell Maya how shiny certain parts of the model will be, and what color those highlights are. Note how my somewhat dull wood is all dark tones, where as my gold areas area left with some color and are much brighter. This map is generally created by desaturating the color map and burning/dodging some areas.
step
8:
Lets take those maps that we just created and now load them into out blinn in Maya. Color map for the color channel, Specular map for the Specular Color channel.
step
9:
Oooo wee, look at that render from cameras 1 and 2. Looking good, and half way done. Now lets set up the coins to finish this up.
step
10:
First of all, the coins are not properly UVd. Choose one coin and duplicate it. Move that coin off to the side (in my demo, you can set all its translate and rotate values back to 0 as the transformations have not been frozen). REMOVE THIS COIN FROM THE COINS GROUP IN THE HYPERGRAPH as our tranfer UVs function will not work if they are in the same group.
step
11:
UV the duplicated coin. My UV layout has the top and bottom planar mapped, and the side is cylindrically mapped.
step 12:
Now, lets transfer the UVs from this coin to all the others so that we have one UV map for all of them, and so that we dont have to map each one individually. Under the Polygons Menu Set, Choose Mesh---> Transfer Attributes, and use the same options that we looked at in the basket ball demo in Week 4. The items in Red are changed from the default.
Vertex Position= off
UV sets= Current
Color sets=All
Sample Space =Component (Local also works well sometimes)
Mirroring=off
Flip UVs=off
Color Borders=Preserve.If you delete the duplicate coin when you are done, make sure that you perform a Delete all by type-->history first.
step 13:
Now that all of our coins are UVd, lets take UV snapshot of one of them from the UV texture Editor Window and open that file up in Photoshop. By searching some images of coins, I was able to create the following color map. Feel free to use photos, scans of your loose change, or simply draw your own from scratch. Its up to you.
Once my color map is in place... time to make a bump map. I'm making a bump map since its quite easy for a human to draw one. They also render perfectly in maya, but cannot be used in real time situations (games), and are limited by their scaling value (the bump depth) which is not baked into the map. In a few minutes we will convert this into a normal map, but we need a bump map first.
My first step is to desaturate my color map. From this starting place, remembering that white=higher and black=lower, I will dodge and burn areas to make sure that I do not get unwanted canyons or mountains. Take a look at how severly I dodged the bottom of the neck where in the color map it was much darker. If I had let this be in the bump map, that would have turned into a crack area instead of simply being a slope that was in shadow when the photo of the coin was taken. Also note how I have drawn grooves on the edges to preforate the sides of the coin.
step
14:
With both maps saved, we can add them to a blinn shader for the coins in maya and take a render. While the bump depth is too high, the results are pretty good:
step 15:
Well, now its time to turn the bump map into a normal map so that it could be rendered in a video game format. To do this we will need to instal NVidia's Photoshop Plugin Filter which I have conviently located in my faculty folder. You can also download it here: http://developer.nvidia.com/object/photoshop_dds_plugins.html
Its a very simple install. First, make sure that Photoshop is closed. Then, double click on the .exe and click through the "nexts" and "I agree to this and thats", and it will be done within about 30 seconds.
step 16:
Once in Photoshop again we can now use the filter! Open the Bump Map file and under Filters-->Nvidia Tools choose the Normal Map Filter. There are several options which look similar to this (somewhat outdated) image below. Sorry folks, but the PC wasn't letting me take a screen shot with the filter window open. Anyways, the Important values to change are in the Height Generation section. Set the Filter type to either 4 sample or 3x3. The Scale will change the depth (I set mine to 7 for this demo). Also, look at choosing Invert Y (not shown in the image below). Inverting the Y will make sure that what was black bumps in, not out. You can experiment with the 3d preview (again, I can't take a screen shot, sorry). But this will show you how the texture responds to various lighting altitudes. When done, hit OK....
....and
you get a normal map!
Again,
lets note the background color which is 128,128, 255 or 8080ff in hex. If
there are any errors in the map, or parts that you wish to smooth out, use
this color value to renormalize the map.
step
17:
Back to Maya now. Attach the new map to the bump2d node and switch that bump node from Use as bump to Tangent Space Normals.
step
18:
Here are two final renders illustrating the coins with just the normal map, and with the color map as well. Tada! we are done.
So now in conclusion we have looked at 2 different ways to produce normal maps:
1:We can transfer the data from a high poly model to a similar low poly model to fake the look of a more developed mesh, using color values to represent changes in the vectors between the two surfaces.
2: Or, we can create a height (bump) map, and convert it to a normal map using the Photoshop filter which looks at the the gradient from any one pixel in grayscale to the surrounding pixel and interprets the amount of change as a vector to be represented by color.
3: Wanna know a third way?... Take a look at my Zbrush Website under week 2. Click Here