What's happened!?!? I have a diamond object that I rendered in SI39 (ior 2,4). It really looks like a diamond, because I see all the polygons on the other side refracted beautifully through the model. But when I render it with XSI's shaders it looks like a piece of plastic. I have the same ior, I have tried very high values in Raytracing Depth and so on. I mean it renders faster, thats good, but the result is bad and that's.....bad. Does someone know anything about this?
I have similar problems with normal glass in XSI. When I import a "glassy" Soft3D scene and render it in XSI, it renders perfectly. But if I create the glass materials in XSI, glass looks more than plastic than glass and it seems to have a terrible refraction index (even if it's set to 1.0). (and yes, it renders faster then). I was told to try higher reflection/refraction values, but it didn't help at all, except that it took much longer to render. But I noticed that shadows of the "wrong" objects are correct (!).
Any ideas?
Show us some samples. I don't see how glass can look plasticy.
-Vijay
Ok, I can show some pictures, but not right now. I can try to explain it first. If you take my diamond object for example; if I render it (in Soft3.9) and look at each polygon (which represent each cut in the diamond), I see lots of other polys (cuts) through it, in differnt colors because the light is refracted very much from different locations in the scene. Now, when I render it in XSI and look at each cut, I pretty much see the color of the surface it's sitting on and not colors from all over the "room". The diamond refracts light less than glass and looks like a piece of plastic, although the ior is 2.4. Rendered in Soft3.9 it sparkles like a diamond, in XSI it sparkles like a piece of plastic (i.e. not at all)
Another thing I've noticed is that if I have a sphere for example with ior 1.3, and a copy of that object with the same ior and place it behind the first sphere, it doesn't refract light AT ALL. I've seen this when I've placed one more object in the scene behind the second sphere. It looks like a transparent object without refraction. You can try it your self.
The color seperation effects you're talking about can't be handled by Phong shaders, if that's what you're using.
Explain exactly the Render Tree set up you have.
You may need to tweak sparkles etc with output shaders but there should be a colour seperation system built into a diamond shader for sure. You might need to add some reflections? Lack of Colour Seperation appears liks your biggest problem and lack of highly flarred specularity. That's if I understood you right.
Let me give it a go.
-Vijay
I think the problem is more of a refraction problem.
Anyway, if you want to, you can send me your email adress in a private message (if you don't want to post it here), and I'll send you a 212Kb JPEG showing my results in both SI3.9 and XSI. I could post it in the gallery, but I don't think it's intended for forum issues(?)
you probably have to turn on back face rendering in the render options panel.
Sergio Caires
Character Supervisor
Digital Animations
Thanks for the suggestion, but I'm already doing that. For those of you who want to, here's a little thing you can try for me:
In Soft3.9, create a transparent (phong) nurbs sphere with ior 1.3. Put some smaller, non-transparent objects behind it(so you'll see them through the sphere when you render). Render it with MR and save the picture. Save the scene.
In XSI, import the scene and apply a new material (phong) to the sphere. Make also this material transparent with ior 1.3.
Render the scene and save the picture.
Now compare the two rendered pictures you have. Did you get the same look on both refractions? If you did; congratulations and please tell me how. If you didn't; well, there you see my problem.
Phong shader irregularities is a known issue with mental ray. You must use a different shading model if you need specular highlights in conjunction with other features. Try the blinn, strauss, cook-torrance, or anisotropic shaders.
Matt
Matt Lind
Animator / Technical Director
Softimage certified instructor
Softimage|3D
Softimage|XSI
speye_21@hotmail.com
Oh come on. The highlights are not really the issues here. I've been trying several times to explain that it is the REFRACTIONS I'm having problems with. It clearly says "refraction" in the headline. I don't want to be rude here in any way, but the only thing I want to know is:
Can I get the same looks on refractions (you know light that bends when it passes through transparent materials) in XSI that I get in Soft3.9? If you try the example I've described above you'll see what I mean...
Thanks anyway.
I've been doing some tests with it and YES, there seem to be a problem with the refraction in XSI. It's like if the ray depth was locked to a small number.
I think it is a bug and you should contact Softimage support about it. Unfortunately, they just cut off the department by half two weeks ago. You might not get the answer you want soon, but you should try.
--
Flord
Senior 3D animator
Buzzimage
I don't think you'll have problems getting support.
I've been calling support everyday for the last two weeks. I haven't noticed any slow downs, and usually get a support tech without wating.
Urp
Is the problem occuring in full renders as well as when you view from within the app? The render region has it's own settings which may be overriding your regular render settings?
Also (I know, I'm reaching here) have you turned your scene's ambiance down to zero?
@Oh come on. The highlights are not really the issues here.
You didn't read correctly. I said that mental ray has KNOWN ISSUES WITH PHONG SHADER IRREGULARITIES. Highlights is just one of the issues. If you don't want to deal with the issues - use a different illumination model. period. Go to softimage support and see for yourself.
Matt
Matt Lind
Animator / Technical Director
Softimage certified instructor:
Softimage|3D
Softimage|XSI
speye_21@hotmail.com
"I've been doing some tests with it and YES, there seem to be a problem with the refraction in XSI."
Thank you. Finally someone who tries to deal with the thing in the software.... It's always good to know that the problem really is there before you turn to the support, so you know that more than one person has had the problem.
To answer Gpfault:
I've tried all possible ways of rendering (I think 
and I'm having the same problems anyway.
To answer Matt Lind:
Ok. Sorry if I upset you. In my example that I described, I only used phong as an example in both XSI and Soft3.9, so that you'd use the same shader types in both applications. I've tried all the shading types in XSI (including blinn, strauss, cook-torrance and anisotropic) together with refractions (have you?), and I'm still getting the same bad results. The look on the refraction itself does not change if you use another shader (for me anyway). Maybe you'll get more light here, and more shade there, but you'll still see the same refractions with all the shaders in XSI.
I've been doing import of SI3D scenes and did notice a difference mainly because they're different shaders. That is, the SI3D phong shader is different code than the XSI phong shader even though they both run under the same mental ray engine.
I haven't dealt with refraction yet, but I have found solutions to the color and shade issues. Basically you have to rebuild your shader as a phenomena and apply a color correction node between the phong (or whatever illumination model you choose) and the surface and shadow inputs of the final material node. The gamma should be set to 0.95.
If I find time, perhaps I'll find a refraction solution (no guarantees). For now, I would suggest getting aquainted with the incidence shader so you can modify the angle of the outgoing ray based on the angle it penetrates the surface in order to match SI3D's appearance. Simply plug the incidence shader into the refraction component of your illumination model (with proper conversions/offsets applied inbetween).
Also don't forget to kill the default light in the XSI scene as it isn't always deleted upon import of the SI3D scene. This can be a cause of 'some' anomalies (even if the light is hidden).
Other things don't import cleanly either. Spotlights, for example, have their spread values set 2x too big upon import from SI3D. Whenever you import an SI3D scene into XSI, make sure to reduce the spotlight spread values in half (eg - a spotlight with a 10 degree spread in SI3D should have a spread of 5 degrees in XSI). Camera lens angles are different too which may account for a portion of the visual artifacts. Check your ambience values as they aren't always set properly from SI3D.
If you're using volume shaders such as bionic light, you won't find a direct equivalent in XSI.
There's more, but i need sleep.
Matt
Matt Lind
Animator / Technical Director
Softimage certified instructor:
Softimage|3D
Softimage|XSI
speye_21@hotmail.com
Thank you. I'm gonna try the things you described.
Please let me know if you do find a refraction solution (I know I'm gonna try
Sleep well.
I don't have the option to render the same scene in SI and XSI, so I can not double check, nor compare what exactly the difference is in rendering refraction.
Not long ago I did the bottle tutorial from XSI's tutorial CD and the refraction worked well. I just did it again and it works great. My suggestion to you is that create a new material to your diamond object in XSI.
Like I said the render looks perfect. I even put extra objects behind it, above it to see how it'll render. Looks great!
Check out that tutorial and try to set up a shader described there.
If, you don't have it I can send it to you!
:::::vik3d:::::
Hmm... I just tried creating a sphere with another sphere and a checkerboard behind it.
I gave it a phong shader and made it refractive, and it was.
Then I tried with cook torrance and blinn and there were no problems making it refractive.
What DID give me problems were the hilights which were hardly there, but that's another story.
It may sound stupid, but have you tried what I just did??
I mean, it worked without any problems whatsoever.