[Tutorial] Discovering Blender Part 4: Baking



Discovering Blender


This tutorial is based on Blender 2.49b.

Prerequisites:

Here I will show you how to bake a normal map from a Hi-res model to a Low-rez one. Then I will show you how to add a new UV channel ready for shadow and AO baking.
As usual we can start with a cube.
Start Cube

Then we add a multires to it

Multirez

…and add several levels to it and keep the catmull-clark type (smoothes the objects while subdividing it). But I must warn you that once a level is added, it will change every lower level even if you delete it later, only undo operation will give you back your original shape. The other level type  subdivides the object (tessellation) and no smoothing is applied thus it will keep your original shape until you directly edit it.

Add Level

Now we can begin editing our rock’s general shape with sculpting tools (grab mode) on an intermediate level for more convenience.

Sculpt Mode

Sculpt Mode

Once the general aspect is given, you can increase the level to the max depending on your computer capabilities, each level will multiply by 4 the number of faces. For a stone like this it is not really useful to go beyond 7 levels. Go to textures (F6) select brush and add a new texture (here I used Musgrave).

Change Brush

Brush Texture

Now you can draw the details on the rock with the draw function.

Stone Details

Once you are satisfied with the result, you can duplicate your object (shift + D) and move it on another layer (M).

Change Layer

Then you can select on the original object which level you want to keep for your low res, If you followed my example and started from the cube you can skip the first level which is the base cube and select level 2 or 3 and apply the multirez, this is not mandatory but if you don’t you’ll have to set the render parameter to the level of resolution that your low rez will use.
On the “new” fist level enter edit mode (TAB), add the seams (ctrl + E). Then select all the faces (A) and then unwrap (U) it.
Split you view if you haven’t already and open the image editor (shift + F10). Add a new image I used here a 1024 which might be a little bit excessive for a simple rock (Important: be sure to be in edit mode and having all the faces selected).

Add map

New image
Now everything is set to begin the baking!
Select the layer on which your hi-rez model is, and select the hi-rez, then keep the shift key pressed and select the low-rez layer and while keeping shift pressed select the low-rez. Now in the scene panel (F10) click the “Bake” tab and select the following options to bake the normals.

Baking Options

Press bake. You should have a normal map with a blue dominance, don’t forget to save it.
Once the map is added to the model with the adequate parameters you should have something like this.

Result

If you see some strange lines that appear at a certain distance you should increase the margin parameter of the baking options. I think this is due to the internal resizing of the texture by the engine (mippmapping) when you increase the viewing distance from the object.

Bad result

Zero margin result

Part 2


Applying UV for AO and shadow baking on several objects.
First apply scale and rotation to every object that you want to use in object mode (ctrl + A) if you don’t you might end with strange results.

Apply Scale

Then select all the objects that will share the same map and enter edit mode (TAB), press U and choose lightmap UVPack.

Lightmap UVPack

Set the options like the folowing picture.

Unwrap Params

Share Tex Space makes all the objects share the same texture space.
New UV Layer add a new UV set to all selected object (do it once only)
New image will create a new image and assign it, as the active texture to all the objects. Margin is the proportion of the texture space between the islands of faces. Needed when baking with margins.

Now you can bake all the object in one shot by selecting them all, but be sure to disable the “selected to active” button if enabled. In blender you can use shadow maps and AO maps as color maps by setting the blending mode to multiply and even link them to the Emit value. Baking AO and shadows is very useful if you have static objects and/or lights in your scene depending on what you want to bake. This way you will gain an extra quality while keeping rendering time as low as possible. However I would not advise to bake normals this way, especially if your scene contains several objects because you will end with a too small amout of pixel to define the normals.

I hope this tutorial will be useful, happy blending!

Want to see an example that uses this model in real time 3D ?

Just look at this demo:

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