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Creating normal maps from a high resolution model is a common task in a game developers work flow. It can add an extra level of detail that otherwise would be impossible within a game environment. Today I will be showing you how to create normal maps in Blender 2.5. The process used to do this is called “baking”, it enables us to project all of the detail from a high resolution model onto a low resolution, or lowpoly game model to create the normal map. This is a relatively painless process that can be done quite quickly once you have the know-how. Let us begin!
Note: Normal map baking requires a recent version of Blender 2.5, which can be downloaded from http://graphicall.org for all operating systems. Baking is broken in the official Blender 2.5 alpha 2 release.
Part 1 – Preparing the models
The first step to creating normal maps, is to prepare the models. This primarily involves UV unwrapping the lowpoly model. Before doing that, though, let’s take a look at the models we will be using today in figure 01-02:
As you can see, we have a highpoly model of a statue, with a large amount of detail, much more than could feasible be used in a game. Then we have a lowpoly version of the same model. To bake the normal map, we must first unwrap the UVs for the lowpoly (the highpoly has no need for UVs and may be left as is) then we need to assign a blank image to those UVs that will become the normal map.
To unwrap the lowpoly: enter Edit Mode by pressing TAB while the lowpoly model is selected
2. Select the vertices shown in figure 3 then press CONTROL + E > Mark Seam
3. Repeat this step for the vertices in figure 4, ensuring the selection starts at the previous seam and continues all the way down to the bottom of the model.
You should now have all of the necessary seams placed to cleanly unwrap the model:
Select all of the vertices that make up the model by pressing A (you may need to press it twice if you previously had anything selected) then press U > Unwrap
2. This will unwrap the UVs of the model, to see them switch your viewport window time to the UV/Image Editor as displayed in figure 6
You now need to add a new image to the UVs simply by pressing the “New” button. If you need to adjust the size of the newly created image immediately press F6 and modify as needed.
Part 2 – Baking the normal map
Let us now bake out the normal map by switching back to the 3D View and then going to the Render Properties:
First select the highpoly model with RMB then select the lowpoly model with SHIFT + RMB
2. Toggle down the “Bake” options under the Render Properties
3. Change from “Full Render” to “Normals”
4. Switch from “Camera” space to “Tangent” space
5. Ensure “Selected to Active is checked
6. Press “Bake”
Upon completion of the bake, you should see the normal map displayed in the UV/Image Editor.
That is all it takes to bake normal maps! It is really quite simple, Blender does most of the work for us. However, in order to really see the fruits of our labor we are going to take it a step further so we may view normal map in real time.
Part 3 – Viewing the normal map in real time
The way we are going to do this is by adding a material to the lowpoly model that will contain the normal map and tell Blender how to use it:
Begin by adding a new material to the lowpoly model, name it if you wish
2.Switch to the Texture panel and add a new Image texture
3. Select the normal map from the buffer as the image source
4. Check the “Normal Map” box and change the space type to “Tangent” from the default “Camera”
5. Change the Image Mapping type to UV
6. Uncheck the “Color” box under the “Diffuse category of Influence
7. And finally check the “Normal” box under the “Geometry” category of Influence
Now we are almost ready to see the normal map in action. All that is necessary now is to change the viewport rendering method over to GLSL for real time shading.
Press N while hovering your mouse over the Viewport to bring up the Viewport Properties
2. Scroll down to the “Display” category and change the “Shading” method to “GLSL”
3. Select the highpoly model and press H to hide it, allowing us to see the lowpoly model properly
4. Press ALT + Z to turn on GLSL shading
You should immediately see a result. If everything is correct, you should see the normal map applied to your lowpoly model in real time. Be sure that you have at least one light in your scene or you will not see anything. Speaking of which, if you move the light around in your scene you will see the lighting change on your model. The normal map is being displayed in the viewport just as if it were in a game.
That is it! You have now baked a normal map in Blender 2.5. Once you have become accustom to the process, it can be done in under five minutes. This is a very useful feature and works remarkably well. If you find your normal map are receiving artifacts then it may be necessary to tweak some of the settings under the Bake panel. I will not get into that today. For the time being, enjoy and happy baking!