Ray traced shadows: problems in material nodes

Support Materials and Textures
1

I managed to create a basic test to simulate hair using a textured object. Here is the version NOT using material nodes (please ignore the lack of realism in the “hair” texture currently):

NO_nodesShadow.jpg600×600 24.7 KB

Note that the shadow is ray-traced and diminishes with the hair length. The trick of course it so ensure that the “person’s face” material can receive ray-traced shadows - as it does.

But, when I do the same thing doing the hair as a nodes-based material, I can get the same look out of the hair, but not the shadow - even with the “person’s face” material ray-traced shadows activated. See below.

NodesShadow.jpg600×600 32.1 KB

Does anybody know whether there is anything special in the material nodes that I do not know about?

AnyMation

2

With the risk of being called impatient (I don’t think I am after a day+), does anybody know what the cause of the above problem could be?

3

the two hair sets do not look anything alike. Are you comparing apples to apples? The second hard edge shadow looks like it comes from a freakin mesh of matted hair, so it should be solid and not diminish. My advice would be to get the hair looking the same first, then worry about the shadows.

Patience is a virtue.

4

Thanks RogwerWickes,

You are correct - I am not 100% comparing apples with apples, but that is where I pick up the discrepancy: the last one is nodes-based, so I did play around with a few nodes to get the colour and texture that I wanted (which is not the same as the first image).

In my simple mind, I have colour and textures with an alpha value in both models. In both of them, the alpha value can be seen in the hair itself, but I cannot get the shadow to comply with the nodes-based alpha.

I am now going to try a simple alpha node and see what happens…

5

I did some tests on two planes a small distance apart from each other and concluded that there is a bug in Blender. The following is a summary of the symptoms of the problem I logged:

When one generates a node-based material, which is UV-unwrapped, and one then adds a blend-texture, the resultant transparent shadow onto another object is incorrect:

  • Using ONLY node-based materials, the rendered shadow onto another object is not transparent:
  • If one adds another “normal” (NON-node-based) material, the transparency now shows up in the NODE-based material’s render, but…
  • Is misaligned due to an incorrect coordinate system
  •  Or, can be fixed if UV coordinates are selected for the <i>NON</i>-node-based material<img src="/uploads/default/original/3X/1/9/19b500530288500a76c023ce67d473ff86566fd5.jpg" width="300" height="300"><br/>