For this unit we were tasked not only to create and UV a model but also to create several maps aswell. Maps are snapshots of specific data required for a model to perform effectively inside an engine. They are layered aspects of detail giving the program an easier way to project the information required without it trawling through all of the models data to find the information it requires.
NORMAL MAPS
A normal map, or Dot3 bump map, is a surface map of the topology of a mesh. It maps out all of your models bumps and ridges for use in place of more polygons on a mesh. By doing this you can take a more detailed topology of a model and place it over a lower poly version of the same model. This will give you a high poly looking model skinned over the low poly mesh.
Maya, again, have implemented a quick series of actions to achieve this, sort of.
For this process I will again be using the example of the same cube I UV’d in the last exercise. As the cube already has Lightmaps this is ready for a normal projection.
I began by duplicating my low level mesh, the cube. On the duplicate I added two edge loops across all three elevations. Next I extruded the centre square inwards a little to add a different, more detailed topology to my mesh. Then I UV’d this model for it’s fresh topology.
Now I have two simple shapes, one of which I extruded from the original and added some detail. Next I will transfer the high detail onto the low, to give the low the appearance of the high. To do this, firstly, I must change the menu toolset from ‘Modeling’ to ‘Rendering.
In the viewport, in object mode, I click on the low poly mesh, selecting it. Now I select the ‘Lighting/Shading’ sub-menu and selected ‘Transfer Maps’.
This opens a new box called ‘Transfer Maps’, in here I can select several different maps to project, for the time being I am only interested in the Normal Map.
The first step in this process has already been done. By clicking on the low poly mesh before selecting ‘Transfer Maps’ the program has already inserted that mesh as the ‘Target’ mesh, meaning this is the mesh the other detail will be assigned to.
So, now I have a target I need a source, this is the second, more detailed, mesh. I clicked on the source mesh menu bar to open it, clicked on the second mesh in my viewport and clicked the ‘Add Selected’ button in the source mesh menu. I know have a source mesh.
Next I need to choose a map type. The next menu down the list is ‘Output Maps’. At the top of the menu are five map options with simple icons displaying what they do, the normal map is the first, labelled, it’s picture is of a sphere covered in what looks like a complex map, giving it the appearance of a golf ball. I clicked on it. This opened a further menu of options including, the maps destination file, format,include materials, map space, and use maya common settings. I am only interested in three.
The first is the file destination. This is obviously where the file will be stored, ensure this is correct and correctly labelled for ease of identification later.
Next is the file format. Targa is the chosen format for this process. From what I can gather it yields better results than any other but this is yet to be proven to me.
Finally is the objects map space. There are two options her ‘Tangent Space’ or ‘Object Space’. Object is for static meshes, something that never moves in your scene. Tangent space, is for objects that move or are animated. As a rule of thumb I choose tangent space, it’s better to have the option than need it.
The last two optional changes are in the ‘Maya common output’ menu, the maps dimensions and the sampling quality. Realistically the maps dimensions is double faceted, the maps width and height, I count them as one as they effect the size and shape of the object, unless you desire a higher poly height to width they will always be used uniformly for a more consistent representation. The sampling quality, on the other hand, is just a drop-down to format the level of detail, sort of like a camera zoom, the higher the multiple the more definition.
The final act on your checklist is probably the most important. In the ‘Target Mesh’ menu, after the name of your mesh there are three boxes, ‘Output UV Set’, ‘Display’, and ‘Search envelope (%).
The output UV set I leave as map1 (default naming). The last two are important. The first, Display, is an option to choose to see the third option, envelope. The envelope is the limit of extent that Maya will look at your models topology. This means that every piece of information on your model must be within the confines of the envelope to be seen and transferred. So some readjustment may be required to fit all of your detail in. The easiest way to do this is to put the display into either envelope, it shows the envelope over the mesh, or both, which shows the envelope and the mesh underneath with all of it’s detail. I don’t think it really matters. If your envelope is too small to cover your entire model adjust the slider under ‘search envelope %. This will directly effect the envelope size in the viewport. In the below right picture I have moved the high poly mesh over the low to ensure all detail will be captured.
Now everything is in place all we need to do is hit the bake and close button, on the bottom left of the transfer maps window. Sit back and wait for the program to bake one set of information over the other.
My results were less than favourable.
I the above pictures the high poly mesh is on the right. As you can see only two of the faces have been transposed onto the low poly version, one of which has a burn around. Apart from the faces being too small and the burn being the correct size nothing else worked out as it should. I will endeavour to remedy this but I am more than worried that Maya cannot even transfer simple maps successfully. I moved on to my model for this project, hoping for a better result on a higher complexity model.
As you can see most of the detail transferred correctly but there is still a lot of work to do. It boggles my mind that a mathematical program(Maya) can build and sustain all of the vetices, edges, topology, and structure of a complicated mesh yet cannot recognise that the exact same shape, duplicated, does not follow any of it’s maintaining calculations for that structure. Leaving you with a blanket map that doesn’t fit another copy of the same shape. I understand that the topology has slight variations, especially in the higher poly but vast expanses of the models map perfectly despite these slight variations. Leaving the question, what happened to the rest of it?
I ran some research into these erroneous burns to find that some of the cause could be from inverted vertices. If these are not allowed to happen why does Maya allow you to continue when they are done. A simple ‘Test’ button would remedy this, available all of the time it will test the viability of the structure of your model. It could also pinpoint the aberration instead of allowing you to trawl, piece by piece, through your model to locate it. Transferring normals in Maya gives is like writing a novel then when you come to publish it every copy you make is incorrect, whole paragraphs have changed just because you forgot to put in one full stop, that the program sees but doesn’t tell you. Infuriating.
In an effort to find a solution within the transfer maps set-up, I changed all of the parameters highlighted above. It didn’t work. The more detail I inputted the smaller the fault was. The lower the larger it became. The same poor map transfer only in higher or lower detail. This points to the obvious conclusion that the real answer lies elsewhere.
I have found a much easier process. Using substance painter. All that is required is to open a low poly mesh in substance. Click on ‘Bake textures’. When the box opens you will see a smaller , black lined, box within it. Check the ‘ Use low poly mesh as high poly mesh’ box, then add your high poly mesh via the folder on the right. Now click bake, bottom right. A low poly version with high detail should appear.
My Blueprint Factory 