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Using Bump Map to Sculpt Details

Author: Dong
Date Published: 2007-04-19
Page Visted: 63301 times
Contact: yangdongmy@gmail.com
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Dear Readers, it is the first tutorial I have ever made in my life. So please excuse me if I made a mistake somewhere in the tutorial. If you are kind enough, please send me an email to correct the wrong information. Anyway, what I will show you is how to use bump map to easily add cool details to a simple model like a bell you can see in the picture.

Let's start with idea seeking first.


Every object you want to make in 3d, you should always start with references. They will give you much better idea when you start actually making the models. I use google to search ideas, or rather pictures. Yes, you can find anything you want. I found a couple of pictures through Googling, showed below:

[Reference Photos for the Bell]


As you can see from the reference, there are a lot of details on the bell and the immediate problem we need to solve is: how can we put on these many details onto the bell "cheaply"? By "cheaply", I mean we need to do it without using 2 million polygons on the model. The answer is: Bump Map. (I use Maya as my modeling package. But the concept is the same with any other 3d applications.) Bump Mapping is a technique where you apply a texture map to a model like a color map. The difference is: bump map is usually black and white and it gives a object "bumps" instead of "colors" like a color map does. And the bump map is applied to Bump Channel instead of Color Channel.

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[First one is the screenshot from Maya. Second one is the rendered image with Bump Map applied.]


1. Starting with a curve.

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[Curve for NURBS Surface Revolve Operation]


2. Choose Surfaces > Revolve (Revolve around Y axis)

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[NURBS Surface Revolve Operation]


3. The resulted surface's "Spans UV" is 7 and 8. We need to rebuild the surface by making "Number of spans U" to "8" and "Number of spans V" to 16 under "Rebuild Surface Options" (Edit NURBS > Rebuild Surfaces).

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[NURBS Surface Rebuild Operation]

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[NURBS Surface Rebuild Surface Operation Result]


4. Change from Perspective view to Top view, and change to component mode, then select vertices according to picture below.The purpose is to select 8 vertices which you can use to pull upwards to form the bottom wave-like shape(the second picture shows the final result you should get).

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[Select 8 vertices]

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[Pull selected vertices up and use scale tool to scale inwards to line those vertices with the curvy shape of the bell surface.]


5. Use Modify > Convert > NURBS to Subdiv to convert the rebuilt NURBS surface into a Subdivision Surface. The subdivision surface will give us the ability to edit in Polygon mode which enabled us to use all sets of powerful Polygon editing tools.

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[Select 8 vertices]


6. Right mouse click the model and choose "Polygon" on the Marking Menu to change to Polygon editing mode and select all the edges at the bottom of the bell. Then use the Edit Mesh > Extrude to extrude the edges inwards. Extrude a few more times and shape the edges to form a thick edge.

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[Select all the edges at the bottom of the bell and Extrude]

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[Result of Extruding Edges to form the thick bottom]


7. Now the object is done. We need to lay out the UV. First Convert the object to Polygon. The purpose of the conversion is to layout UVs easily with polygon menu's excellent UV editing tools. The UV editing tools with Subdivision Surface menu is somewhat limited at the moment.( After we have done the UV with the Polygon surface, we can convert the polygon object back to Subdiv surface, and the Subdiv surface will inherit the UV from the Polygon object. Conversion menu is under: Modify > Convert > Polygons to Subdiv. )

(Note: Remember to set the "Tessellation method" under "Convert Subdiv to Polygons Options" to Vertices, so the resulted Polygon Surface will have the same number of faces as the Subdiv Surface. And we will not experience problems later on when we try to convert back to Subdiv Surface.)

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[Convert Subdiv to Polygon]


8. Change to Component Mode and select all of the faces of the object, then go to Create UVs > Cylindrical Mapping, and use Polygon UV editing tools to transfer UVs around to get a nice and even UV layout like the picture showed below.

Once you are done with the UV, you can then convert the polygon object back to Subdiv Surface. (Second picture) As you can see, the UV we got from editing on the Polygon Surface has been inherited perfectly to the Subdiv Surface. A checker pattern has been assigned to the surface to see if there is any distortion with the UVs. In this case, it is quite ok for our purpose.

The next step is to paint the texture maps we need to bring out the details of the model. First we take a UV Snapshot of the model. In short, it will create a JPEG image with a balck background so you can use it as a guide in your painting program (such as Photoshop) while you are painting your texture maps.(Third picture shows the menu of UV Snapshot) Menu for UV Snapshot: in the Texture Editor, go to Polygons > UV Snapshot..

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[Layout UV with Polygon UV Editing Tools]

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[Convert Polygon back to Subdiv Surface]

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[UV Snapshot menu]


9. As you can see, the Bump Map is just a black and white image with some grey in some areas. In Maya, complete black means no bump and complete white means full bump. The grey means value in the middle of complete black and white. All the dragon and patterns are coming from Dingbat Fonts. Dingbat Fonts, in case you do not know, is a special kind of fonts which is not letters like "A, B, C, D ...", but rather graphics as letters. You can rasterize the font and edit them as well, just like any other 2D graphics. By going this way, you can get complex patterns in no time. Just do a simple Google search, you can find loads of Dingbat Fonts on the net.

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[Bump Map made in Photoshop]


10. In this case, Color Map is really just a yellow color plus a Cloud filter applied. Of course, you can add all sorts of effects in Photoshop with different filters and hand painting them as well.

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[Color Map made in Photoshop]


11. Once you finished the maps, you can apply them to the model. The picture below shows the shading network in Maya. The Color Map is connected to Color Channel, Bump Map is connected to teh Bump Channel.

You can play with the bump values and other sttributes to get completely different looking bumps and effects.

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[Shading Network in Maya]

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