Question about baking textures with alpha in Cycles

Support Materials and Textures
1

Blender Cycles does not seem to be able to bake textures with any alpha in them whatsoever (unless texture area is unmapped).

I search in the Bug Tracker and find this https://developer.blender.org/rBf3505ab771184877413cfa11336da2ccc1da36ee

It seems any alpha baked in Cycles is pegged to 1.0

Is this expected behavior or have I missed something somewhere?

I’ve tried both PNG and TGA, both with RGBA.
Render -> Film is set to Transparent, so that the World Background is transparent.

My test case is a leaf texture on a flat plane, with nodes like so: http://blender.stackexchange.com/questions/6416/transparent-image-textures-in-cycles

I’ve even tried it with a texture that is completely transparent (it comes out a solid sheet of black).

2

I am interested in an answer for this as well! Baking alpha in cycles is very useful for baking procedural animated effects (with open shading language) into textures.

3

While things are shuffled around some, nothing seems much changed compared to what was said in mentioned developer.blender.org thread:
/intern/cycles/kernel/kernel_bake.h


        /* write output */
        float output_fac = is_aa_pass(type)? 1.0f/num_samples: 1.0f;

        if(sample == 0)
                output[i] = make_float4(out.x, out.y, out.z, 1.0f) * output_fac;
        else
                output[i] += make_float4(out.x, out.y, out.z, 1.0f) * output_fac;