Well, I made my own little shader swatch scene thingy, I had to (I was using spheres prior to this, don't ask, just chalk it up to laziness and back away slowly). Since I'm rendering out swatches, thought I'd write about it, might help a new user, who knows :o).The mia_mat_x is one of my favorites, if not my favorite shader, yeah that's right I said it, it's out there now so deal with it. It's a very versatile shader, from glass, to plastic, rock, wood, metal , even the crud stuck in that creepy guy's teeth, it can pretty much do it all. Migrating over from shaders like the Maya Blinn where there are independent channels for qualities like reflectivity and specularity, the mia_mat took a little getting used to since it's a physical shader, good thing the attributes are self explanatory . I tried the whole "use a preset and reverse engineer 'em" method to know what makes that particular "look" tick. Well, that didn't work out too well as I wasn't familiar enough with the shader's default attributes to even know most of what was changed so I decided to poke around 'til I knew what attributes did what.
Ok, so I mentioned specularity and reflectivity, in the real world those two properties should be the same, after all, aren't specular highlights just "fake" reflections of light sources? With a Blinn shader, you can kill the reflectivity on it and still get highlights, kill the reflectivity on a mia_mat and you get a matte surface. If you were to check on 'highlights only' under the mia_mat's reflection attributes, you would get a material that reflects light sources only, similar to the Blinn setup I mentioned above.
Well if you can achieve similar looks a lot of the time wtf why are you such a mia_material cheerleader? I'll tell you why, it's easy to use and there's a lot you can do with it, there's the built in AO feature, view dependent reflection, reflection and refraction falloff. Anisotropic reflections (hello brushed metals ^^) , quick and dirty translucency, paper thin or thick transparent surfaces, Transparent shadows or caustics on a per material basis, creating "cutaway wall" effects with the backface culling option etc.
My routine material creation checklist: note: gamma correct colors and texture files (forget it and you die, that's just how I roll <3) Block out:
______
-color
-reflectivity (this covers specularity, as you can plug a specular map into the reflectivity or reflection color, I prefer leaving the reflection color slot free)
-transparency
Attributes like bump, displacement come after, namely displacement, since bump is much lighter. Luminosity, anisotropy and translucency are "extra" so to speak as they are less common than the above mentioned qualities.
Test, test, test, then take care of the secondary features, like blurring, falloff etc. Beef up the render settings for a sec to final or near final quality (reasonable resolution though) to check just how low I can keep samples on shaders and get away with it. Scribble that down in mah trusty notepad and all should be well.
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Hi there. Thanks for the great info on the blog - I've been wolfing down the material tutorials.
ReplyDeleteOne question on the MIA(X) workflow that's really got me stuffed at the moment - How do you approach the BRDF settings? There's so much about the reflections that are affected by this it's hard to know if you've got their settings close unless you've got some kind of BRDF estimation and for that I'm guessing.
The whole BDRF topic is pretty opaque. Googling gives a hundred academical research papers and links to BRDF databases with meaningless values that you can't just drop into the box like an IOR value. Or am I missing the right resource sites?
Any help would be appreciated!
Thanks,
Ian
Any pointers would
Yeah I understand what you're saying, I haven't found any such resources either but then again I can't honestly say I put a lot of effort into the search.
ReplyDeleteThe way I see it, the BRDF settings place min/max limits on the overall reflection value based on whether you're viewing it at eye level or at a perpendicular angle. And the BRDF curve controls the transition between the two values.
I pretty much just eyeball a general reflectivity value and use the BRDF sliders to clamp it down after I Googled a couple references.