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AlexK
07-20-2004, 12:54 PM
Hello out there,
I was wondering if the is a material that would output just shadow information. You know for layered rendering purposes. I render my character and have this Shadow Material applied to my floor. Messiah then puts out an image with the character on black, but with visible shadows on the floor in the alpha channel. Does this make sense to you? Something like Maya's "Use Background" material.
Maybe a quote from the Maya docs clarifies my question:
The Use Background shader allows you to mix computer-generated objects with scanned images in a seamless way. An object with a Use Background shader does not show up in the scene; wherever that material is, you just see the background image of the scene. However, shadows can fall on the material, and if it is made shiny, it can reflect other computer-generated objects.

For example, let's say you scan in a picture of a tree, and put that on an image plane. You can then create a tube to "stand in" for this tree in the scene. Position it so that it lines up with the tree, and assign a Use Background shader to it. When you render, you will not see the tube. Rather, you will see the tree in the background image. But if a computer-generated object should cast a shadow on the tube, it will appear to be cast on the tree. And if a computer-generated object should pass behind the tube, it will sppear to be passing behind the tree in the background image.

Is this possible in Messiah? Maybe a self made shader flow? Or is this something that has to be coded? If so, Thomas maybe you could integrate it to your shaders collection soon to be released?

AlexK
07-22-2004, 06:54 AM
As Thomas stated in the Messiah Render thread:
You should be able to do that already with some clever combination of shaders.
and he tried to gave a hint (which I am still to bone headed to decode :shrug: )
Question: "What's white and receives shadows?" ... :-)
Well anyone who has any ideas?

AlexK
08-02-2004, 02:59 PM
I thought I'd bump this one up, because I think a shadow material would be very handy and I didn't come up with a solution till now. :sad:

tjnyc
08-02-2004, 04:21 PM
You can accomplish the same thing with Camera Mapping. It doesn't look like messiah supports it though. Or you can place dummy objects and match the view to the image and and just set unseen by camera, it will still cast shadows. You will have to composite in the shadow to incorporate into the final image.


Cheers,

JoeCosman
08-02-2004, 04:44 PM
I think what he means is a white shader attached to everything....which will only give you shaded value information.

set diffuse to 100 (diffuse Falloff) to cancel any shading on the object.

also, you can render a no-shadow version to cancel the terminus caused by the diffuse pass.

AlexK
08-02-2004, 06:03 PM
I see thanks, guys. Not quite what I was hoping for, but, well, you can't have everything, can you? :shrug:

MoodyB
08-02-2004, 11:57 PM
If I've read MarvinTMartian's post properly, he's asking for an equivilant to Lightwave's ' shadow alpha ' mode.

MoodyB
08-03-2004, 12:01 AM
You can accomplish the same thing with Camera Mapping. It doesn't look like messiah supports it though. Or you can place dummy objects and match the view to the image and and just set unseen by camera, it will still cast shadows. You will have to composite in the shadow to incorporate into the final image.


Studio v2.0 ( cant remember if 1.5 had it ) does support Front Projection Mapping as a texture mapping type ( same thing as camera mapping, I think ) You just need to remember to front projection map your background material as well as the objects' material.

tjnyc
08-03-2004, 12:39 AM
Front projection mapping in general is a separate mapping function than camera mapping. Camera mapping is basically a FIXED front projection mapping, so you can rotate the camera and the image map that is applied will distort with the prespective view, very good for compositing. I don't know if messiah's FPM is fixed or not, it doesn't state so. However, since messiah does support Front projection mapping then MarvinTMartian you can do what you were asking for, but via a static camera view. I'll do some test to see if is FIXED or not.


Cheers,

tjnyc
08-03-2004, 12:51 AM
Well, I did a test and no it isn't fixed, so it isn't Camera Mapping.

Cheers

MoodyB
08-03-2004, 02:13 AM
Front projection mapping in general is a separate mapping function than camera mapping. Camera mapping is basically a FIXED front projection mapping, so you can rotate the camera and the image map that is applied will distort with the prespective view

Sorry, my bad. Now I know the difference though :)

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