Extreme Rendertime with Mix2Colors and ArchiMat

[shushens]

Hey guys! I am having a problem that I would like to hear your opinions on.

I am trying to texture a car and eventually I started to work on tail-lights. Used mix2colors to mix 2 ArchiMats and also used a bumpmap. With a phong and the bump, a decent sized render region is rendering pretty fast (in 3-4 seconds). As soon as I mix 2 ArchiMats with Mix2Colors with a bitmap as weight, that same sized region is taking about 20 minutes to render! If I simply hide that one tail-light, the whole car with everything else is getting rendered in a matter of seconds. This is very weird and I am not sure how to solve it. Please give me some advice. Other than diffuse colour and transparency, I haven't modified the ArchiMats in any way. There is no blurry reflection/refraction.

I am using Intel Q9450, 4GB Corsair 800 MHz and GeForce 8600 GT with Windows XP x64 SP2 and XSI 7.5 32bit. There is also another odd thing happening during rendering this tail-light. In the middle of the rendering process, CPU usage is sometimes coming down from 100% and RAM usage is also a mere 1.5 GB in average. This does not happen if I hide this light mesh and render everything else.

What can be so wrong with this simple compound?

[owei]

Hi..!

Extremely difficult to make any suggestion. Can you isolate your backlight and make a little scene and upload it anywhere..? Having eyes on your construction will perhaps give some hints..

cheers,
oliver

[Letterbox]

For these kind of oddities, i would first suggest removing the shaders and re-doing them, and it does not sound like a complex one.

Then I'd go thru a process of elimination, removing each connection, and rendering, seeing exactly where the rendering hit actually happens.

with that information either you or someone here will be much much better placed to to figure out why.

Cheers
Terry

[shushens]

First of all, thank you for the swift response. Of course I can upload the thing. I can't include the HDRI, because it's too big. But I am sure you guys have your own libraries

Here it is:

http://www.mediafire.com/?sharekey=e5a9 ... f6e8ebb871

I will try to dissect it myself as well and let you guys know. Indeed surprising!

[Letterbox]

Here is a quick and dirty solution, that does not explain why, but does get you a solution. if the mix is being driven by an image, why not make a render channel for each arch material then just comp them? Thinking about it i think its more to do with the trans on the work, as if you dont do it is it ok then?

[origin]

I had a look at your scene.

You shouldn't mix two transparent materials like that.
If you use two diffrent phongs with transparency set, it will render forever like with mia_mat.

Take your transparency to 0 in one/both mia_mats and your tailglass will render in a second.

What are you trying to do ? Change color on some parts of tailglass ?

Then try to use your mask image plugged into weight of mix but plug MIX it to color/transparency/reflection/whatever port of ONE mia material. And don't plug any material into base color/weight, just use pure colors or textures.

one sidenote, color glass look more real if you leave transparency color as white, and play with end color and distance in mia_mat->optimization->refraction->falloff

[shushens]

Understood! Thank you very much, both of you! I did not learn Mental Ray the traditional way; just by trial and error. So things like that happen sometimes.

I really don't want to make passes for such a tiny thing. I will try to use one ArchiMat and connect a Mix2Colors to its diffuse. Let's see how that goes

And thanks for the extra tip, origin! Much appreciated! It was originally white, but then I started to fool around.

[origin]

no prob

check http://www.mentalimages.com/fileadmin/u ... design.pdf

or in your SI install dir doc/mental_ray/shaders/architectural

its full of examples/howto's and images illustrating all the mia_mat options

[shushens]

This is what I am getting. This time, it's rendering in just a few seconds, but the darker colour in the middle is gone. It is in the Mix2Colors, but it's not showing in the final render. I have no idea why! If I take a Lambert instead, both colours are showing pretty well.




Sorry if the high resolution is a pain. I posted in haste.

[origin]

don't map translucency, plug your mix map into transparency level or transparency color. Please check the link I provided, all the info about glass is there, with examples.

[shushens]

Thank you! I did not think plugging it to refraction colour would be necessary though. If it can take one colour and apply white transparency on that, why not the other one? But plugging it to the refraction colour did it. I did read the manual before, but I am really not the manual reading kind, if you know what I mean . I will go through all of it again now.

I have a question which is a little out of context. Sometimes I see a colour in an image which I want to match by some material in XSI. But the way Photoshop shows RGB and the way XSI does are not really identical. How to I connect the two types of representation? In Photoshop, those are floating point numbers. In XSI, they are 8 bit values.



Last but not least, any suggestions on how to make this look more taillightlike? I can post the entire WiP here if you guys are interested. It is going to be a big scene, but so far I am only making the car.

[origin]

You plugged your mix into translucency port and translucency is not the same thing as transparency.

refraction color drives level of object transparency. Change your color space in prefs-color space to HSV, its better to control than RGB. Then the V will drive your input value (e.g. level of transparency, level of reflections...) With rgb its hard to tell what value color has got.

pdf I gave you is not manual, its more like tutorial with alot of examples... you should stop your work and read it

Check if your files from photoshop are written with some color profile (srgb/your monitor/..).

You may need to set your image color profile to Linears/RGB if your textures look washed out.

But you will have to read MANUAL about gamma thing which aint so easy to understand

[shushens]

I am reading it now

No no, that's not what I meant. I do know about colour profiles and everything. I am trying to say, suppose I have a picture of a piece of cloth, and I want something in XSI take that same colour. So I opened the picture in Photoshop, and from info palette, noted the R,G, and B values, but then how to I input it to XSI? XSI's RGB representation is in 8bit, but Photoshop does it with floating point numbers.

That's what I want to do. I just want to pick the colour from a photo.