Maya 2013 Rendering shadows through alpha maps

Ricky

Hi there, I've decided to ask this question now after much research and still no luck. All I want to do it render a scene that has 2 materials. One material is:
Blinn Shader (Customized)
Diffuse: Targa, 2048x2048, 24bit
Specular: Targe, 2048x2048, 24bit
Bump (Normal): Targa, 2048x2048, 24bit

The other shader is:
Blinn Shader (Customized)
Diffuse: Targa, 2048x2048, 24bit
Specular: Targe, 2048x2048, 24bit
Bump (Normal): Targa, 2048x2048, 24bit[/I]
Transparency (Alpha): Targa, 2048x2048, 24bit (Alpha is Luminacy is checked in color-balance tab. Shadow Attenuation set to 0)

Renderer is Mental Ray (Maya 2013), enabled Raytracing, Global Illumination, Caustics, Final Gather, Ambient Occlusion. 1024x1024 render area, Production Quality.


Problem:
When rendering, the shadows cast by lights (directional light) are ignoring the alpha map, casting a shadow of only geometry. If seen many tutorials all pretty much saying the same thing to do this. "Turn Shadow Attenuation to 0" etc, but nothing is working for some reason... I'm sure I've done this before too which is the most annoying thing.
Using all of the above information about the maps, file types, render settings, etc, can anyone please help me figure out what is wrong here?

The only other things I can think of trying is to use .png with transparency on the diffuse in Photoshop because that seems to be what tutorials are using, but I personally was always taught to use .tga. However, .png with transparency, nor .png with alpha map in channels is working. Always either come out with same result, or mental ray rendering the geometry as black with no alphs at all (controversial to Maya's viewport which is even more unusual to me..)

Any help would be greatly appreciated!!

gray

turn your alpha into an rgb image with no alpha channel and apply it to the transparency channel of your shader.

mental ray only likes images with rgb channes in most cases.

also i would use native mental ray mia_material_x not maya shaders.

Ricky

Sorry I forgot to add that they were all RGB images. However I think i've found the problem; Global Illumination. It seems if I turn this off it works just fine suddenly. Although thats not exactly desirable because the illumination does so much for the image overall.

I will try the mia shaders instead and see if there is any difference there. However what are the reasons for doing so? Do they have better render quality? Or just ensuring more stability during rendering?

gray

just switch to mia and it should work fine.

gray

Ricky wrote: »

However what are the reasons for doing so? Do they have better render quality? Or just ensuring more stability during rendering?

they have far more integrated mental ray features exposed and are fully native shaders. apposed to ports to mimic maya's shades.

the same advice would be true if you were useing vray or renderman etc.

Bellsey

Mental Ray generally has two types of shaders:

mia: mental images architectural (shader library)
mib: mental images base (shader library)

mib are the main base shaders for Mental Ray.

mia material shaders are designed to support most materials used by architectural and product design renderings. It supports many hard-surface materials such as metal, wood and glass and physically accurate.

In Maya you will notice both mia_material, and mia_material_x shaders.
There isn't any difference between the actual functionality of these 2 shaders, they are identical. The difference is the _x shaders has more in/out ports, and additional parameters that makes working with them a bit easier.

Ricky

Ok thank you very much for the help guys, problem solved