In Blender, rendering transparent faces is done in a separate render pass. First it renders all solid faces. Then all transparent faces are rendered in a temporary buffer, which then gets added over the solid render buffer using alpha. To save render time, only transparent faces that are in front of a solid face are processed.

However, this gives 'seams' when a transparent face is partially occluded. The antialiased pixels then have - for example - both alpha value 0.5, which gives a new alpha value of 0.7 when 'alpha-overed'.

To combine these buffers more efficiently, not only alpha has to be stored, but also information about where samples originated within the pixel. This is now done with a bitmask, which allows to verify if half-filled in pixels either are adjacent halves (then add alpha values) or on top of each other ('alpha-over' alpha values).

The images show Solid strands rendered on top of a Ztransp plane.

Note: when using an extreme blurry sample filter like "Gauss", the sample masks don't work well. Most other filters - like "Mitch" work pretty good still.

In spite of all innovative work being done the past decades to get good quality 3D imaging, architects prefer to stick to the old drawing board style perspective. ;-)

Effectively it means that the camera is always aligned to the horizon, so vertical lines appear all parallel. In order to get a full building nicely pictured, the frame ("viewport") is being shifted then.

That trick is now available in Blender's render too: (code + movie, Wybren van Keulen)

download.blender.org/demo/test/2.43/lens_shift.mov

The option "use Tangent" for shading, only could create proper Tangent vectors when a Mesh has UV vectors. Now a Tangent can also be derived from the "Orco" (if that's available). This option actually converts the orco to polar coordinates (like a sphere mapping) and uses that as UV. Result therefore will be always tangents aligning with the Z-axis.

Blender normal map support (added in 2.36) was limited to planar mapping, using code that only supported view-aligned normals.

Now normal-mapping supports "Tangent Space" as well, which allows a correct new normal to be calculated all over a surface, independent of view.

This image shows a subsurfed model of a head without and with a normal map. The model and normal map are from the ORB program, which can be still located here: engineering.soclab.bth.se/tools/177.aspx

Since this type of normal mapping requires external tools too, normal mapping now is fully compatible (previously the scale of the Z vector differed).

Note: enable this option with the new Material Shaders Panel button "NMap TS", which will also invoke calculating tangents on converting the Blender Scene to render data.

Demofile: download.blender.org/demo/test/normalmap_tangent.blend

(Patch provided by Alfredo de Greef)