Mattes and Self Shadowing

[andyp7]

Hi Guys,

Got a bit of a problem with mattes, I have attached a picture of what I want, basically I would like to disable self shadowing on my objects that are matte shadow objects is there a way to do this?

When I tick "don't cast shadows" the object still casts shadows on itself.

Any assistance is greatly appreciated.



Cheers,

Andy

[Morbid Angel]

is that a particular pass you are talking about? if you use matte shadow pass it will give you this result.

[signet]

Hey,

Im working on Andy with this particular job.

The problem is we need to cast shadows on to longish grass. But as you can see the shadow on the matte grass isnt solid. I hope it makes sense from this string of images.









Best,

Mike

[jordanw]

I think you are confusing a projected shadow (on the ground from the teapot) and the light not lighting faces (the dark side of the teapot). The light not lighting the teapot is not a shadow, its the light intensity being reduced due to the normal of a face pointing away from the light.
You may need to do another pass (or an extra texture Render element) with a falloff material set to shadow/light to get the parts of the grass that are not being lit by the light because of normal direction.

The bottom image should be fine to add shadows to the grass as the other sides of the grass shouldn't be affected by light... unless of course you have translucent on the grass!

[signet]

I dont really care about the teapot. All i want is a solid shadow over all of the grass which is being blocked by the teapot.

[jordanw]

Yes, but i was just using that as an example as it was more clear... you need to transfer the idea to the grass, the theory is exactly the same.

The parts that are not solid in your grass shadow pass are not shadows so they are not rendering white in you pass. Its a property of the shading method that makes the back side of the grass dark. so you might need to use a falloff material as i mentioned above.
The solid black you are seeing in full render of the grass (3rd one from your last post) is a combination of shadow from the teapot on the grass, shadow from the teapot on the ground and the shader on the grass rending black as result of the normals facing away from the light source (NOT shadows, as far as render elements are concerned)

Otherwise the last image you rendered is perfectly correct (as far as telling you where the shadow from the teapot is falling on the grass).
If you render your grass with no teapot, then use the shadow pass you have as a mask to darken your grass image you will get the full black area you are looking for.
Why would you need such a pass anyway?