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I'm creating assets for Unity3D. Reading and searching on Internet, even here in Blender Stack Exchange, i understand that the best way to bake (in order to optimize and have still good quality) is using the Blender Render instead of Cycles Render.

For this reason my question is related to Bias and Distance

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I baked a lot but i can't still understand what is the correct meaning of these 2 stats; i search from wiki to sites like this one Baking normal map - distance and bias difference? but i can't focus the point (damn my mind ^^).

What does each of them help to?

I know the Bias from wiki "Bias towards further away from the object (in Blender units)" . . . but this . . . What does it means?

What is their role in order to improve the quality of my bake?

Is the "Distance" similar to a Cage?

Thank you a lot for anyone will help me to understand this thing

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Distance is the distance between the High poly object and the low poly object (in blender unit).

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Note that the distance is only taken into account on the Z axis , and the low poly mesh must be directly under the high poly mesh.
if you do any of the above wrong, the result will be an empty baked image.

Setting the distance too low will make your details not appear on your final baked image since the rays will die halfway before they reach the low poly mesh.

enter image description here

The bias is only related to the high poly object, it controls how much of the geometry is preserved , anything after the bias is cut off.

The black lines are where the rays start being fired down to the low poly object, the rays start from lowest vertex of the high poly object.The rays' length is determined by the distance value.

The red line is the bias distance,it also starts from the lowest vertext of the high poly object, but is fired to the opposite direction(upward).

The details between the black line and the red line are preserved and will appear on the resulting baked image.

The details after the red line (greater than the bias, shown in blue) are lost , and will appear on the baked image as if that area was a flat surface.

enter image description here

Setting the bias value correctly is important when the high poly mesh has curved,round surfaces.

enter image description here Please feel free to edit this answer and correct it.

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  • $\begingroup$ Does this mean that higher bias will give me a better result (more detailed)? Of course this will be capped from the shap of high poly $\endgroup$
    – Fuboski
    Jun 6, 2016 at 22:12
  • $\begingroup$ I added an example of the bias, see how it appears flattened on the bake result. $\endgroup$
    – user2816
    Jun 6, 2016 at 22:15
  • $\begingroup$ Sorry i would ask you a clarification; as you said if you put a value too low for distance, your normal won't get details. Why if i put 0.000 in distance i get always something detail and if i use 0.001 none? $\endgroup$
    – Fuboski
    Jun 10, 2016 at 20:28
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    $\begingroup$ 0 is not interpreted as a distance, it will always bake. it's useful when the bake doesn't give the results you want with only one high poly mesh. for example you can bake highpoly1 to lowpoly1 , and then you bake highpoly2 to lowpoly1 , but highpoly2 has complex geometry and you only want the lower part of it to appear on the bake , so you first uncheck the option clear to keep the old bake , and you lower the distance to only get the good part which is the lowest part, here i baked the ambient occlusion. $\endgroup$
    – user2816
    Jun 10, 2016 at 21:07

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