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MANorth
02-03-2007, 04:13 AM
I've been playing with the new arch shaders in XSI 6 and they seem to have a lot of potential, but I've run into a few things that don't seem to work as advertised.

1) How do I get the physical sky gradient out of the alpha channel? According to the help, checking "use background" but without a background will give a black background for compositing. But this doesn't work, as far as I can tell. I've checked it, unchecked it, turned off the background in the environment stack, etc. but I always get a gradient in the alpha.

2) The round corners node will not work when plugged directly into a material node. It has to be plugged into a shader first. But the arch shader (mia_material) doesn't have a bump port. On XSIBase, Daniel Rinde has shown how to modfiy the SPDL in order to add a bump port, but this solution seems to give me problems with FG. I get black spots in the render until I remove the bump port. So, no round corners with mia_material, an odd situation. (Discussion of this seems to have sort of died at XSIBase, so it could be I am uniquely incompetent here.)

3) The simple tone mapper is supposed to receive a preview image, the use of which is described in mental ray's extra docs on the arch shader library. But if I try plugging anything but noicon into this it crashes the render. The preview should allow for easy calibrating of the tone mapper, but I can't make this work.

Am I just botching this, or are there some real problems here?

wurp
02-03-2007, 10:37 AM
I've been playing with the new arch shaders in XSI 6 and they seem to have a lot of potential, but I've run into a few things that don't seem to work as advertised.

1) How do I get the physical sky gradient out of the alpha channel? According to the help, checking "use background" but without a background will give a black background for compositing. But this doesn't work, as far as I can tell. I've checked it, unchecked it, turned off the background in the environment stack, etc. but I always get a gradient in the alpha.


well, why do you need to kill the gradient in the alpha? Im sure there is a way but the sky will always be behind everything else so why does it need need an alpha at all, just set the alpha to white in the fxtree or something.


2) The round corners node will not work when plugged directly into a material node. It has to be plugged into a shader first. But the arch shader (mia_material) doesn't have a bump port. On XSIBase, Daniel Rinde has shown how to modfiy the SPDL in order to add a bump port, but this solution seems to give me problems with FG. I get black spots in the render until I remove the bump port. So, no round corners with mia_material, an odd situation. (Discussion of this seems to have sort of died at XSIBase, so it could be I am uniquely incompetent here.)


try this setup, I think softimage made a misstake when writing the spdl for this shader, its supposed to have a colour-output according to the MI definition files, I logged a bug about this already. btw, this has been rendered with FG already.http://www.ericknelson.com/wurp/rounded_corners.jpg




3) The simple tone mapper is supposed to receive a preview image, the use of which is described in mental ray's extra docs on the arch shader library. But if I try plugging anything but noicon into this it crashes the render. The preview should allow for easy calibrating of the tone mapper, but I can't make this work.

Am I just botching this, or are there some real problems here?

again I dont see the problem, works fine here. Note that you are not supposed to plug an Image-node into the shader, just plug the clip in there, select the camera and open the rendertree to do this.

http://www.ericknelson.com/wurp/tonemapping_background.jpg

MANorth
02-03-2007, 05:50 PM
Thanks, wurp. As for no. 1, I want to composite another sky image into the background, which is hard if there is a gradient there. It's also hard to render parts of a scene and then composite if there's a gradient in the background alpha. As for no. 2, I've tried that workaround and it still gave me the FG problems, but I'll have another go. As for no. 3, I must just be doing something wrong with the preview I'm trying to plug in.

wurp
02-04-2007, 01:10 AM
I see what you mean now about the gradient in the alpha, I just tried and it works if you just take a color_share node, set its rgba to 0 and plug that into the "background" slot of the physical sky in the rendertree, it still lights the scene but the sky itself shows up as black when you render.

about the FG issue, maybe post a picture? These shaders are from mental images by the way so if there is a bug in the actual shader there is little softimage can do other than report the bug to MI.

MANorth
02-07-2007, 12:06 AM
I'm attaching a screen shot of the FG problem. I get these black dots and the warning : RCFG 0.4 warn 542009: finalgather ray returned NaN for the finalgather point at pixel 790.157 482.542 whenever I run the arch shader through the rounded corners node. They clear up if I remove the rounded corners node.

MANorth
02-07-2007, 01:56 AM
This is the issue with the physical sky background showing up in the alpha. It does it even with the color share workaround described above. The help for the physical sky shader says in relation to the "use background" option, "If this option is on but no background has been set, the background of the rendering is a transparent black (suitable for external compositing)."

wurp
02-07-2007, 09:28 AM
it DOES work mate, you need to plug the color_share node AND enable "use background"
this way the sky will light the scene still but not show up in either RGB or alpha channels...
see attachment..

as for the black dots, this is a problem I've seen before, but with other shaders, I didnt test the roundcorners shader that much yet but I did render simple scenes with the arch-shader combined with roundcorners, and using FG too, and so far no black dots, are you sure you are not using any other weird shaders that might cause the black dots?




This is the issue with the physical sky background showing up in the alpha. It does it even with the color share workaround described above. The help for the physical sky shader says in relation to the "use background" option, "If this option is on but no background has been set, the background of the rendering is a transparent black (suitable for external compositing)."

MANorth
02-08-2007, 02:12 AM
Wurp, I tried with the "use background" checked and unchecked. It didn't make any difference. As for the Fg problem, I don't have it as long as I don't mess with the round corners shader. Connect it, get the dots. Disconnect, lose the dots. I have messed with the FG settings a lot to see if I can solve the problem there, but no luck so far.

CiaranM
02-08-2007, 02:40 AM
For your black dots see here:
http://vol2blog.blogspot.com/2006/08/nass.html

JDex
02-08-2007, 02:59 AM
For your black dots see here:
http://vol2blog.blogspot.com/2006/08/nass.html

Thanks 1,000,000,000 times for pointing this out!

CiaranM
02-08-2007, 01:49 PM
Thanks 1,000,000,000 times for pointing this out!

Thanks to Mr. Laforge! :thumbsup:

MANorth
02-09-2007, 12:08 AM
Yes, it is definitely a NaN problem. This is the error message I get. Thanks for the tip.

As for the physical_sky issue, here's what I've been doing wrong. I've been adding the shader to an environment in the pass, and then going to render>pass>edit>initialize physical sky to synch up the light direction with my sun. But this gives me two copies of the physical_sky shader and, among other things, writes the sky gradient into the alpha no matter what I do. If I just initialize the shader or just add it manually to the pass then I can get a black gradient.

Thanks, wurp, for struggling with this.

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