Renderman reflections - am i crazy?

#1

Hello there all. So I’ve been doing a side project with renderman at home after work. I was a lighter for a year or so before now and got pretty good at Vray. Now am I insane, or… is there something about Vray (even Mental Ray for that matter - so maybe what i mean to say is “raytracers”), that simply produces nicer reflections. I can’t quite put my finger on it. I was wondering if anyone could shed light on my conundrum? Throw some gloss maps on a Vray or Mia material, pop in a light and an environment light and there’s this nice contrast to the reflections - like theres this dynamic range in there thats visually pleasing. Do the same in Renderman and its like… its basically the same thing… however… theres this murkeyness to everything - i think?

This isnt Vray vs Renderman. I’m just wondering if I’m crazy? Anyone know what the difference is ? Yes I know one is Reyes and one is a Raytracer. Why do the different implementations cause different results? Has anyone got tips for making reflections sing in Renderman?

#2

Why do the different implementations cause different results?

Well, you have the answer, you just don’t know the why.

Technically this result is similar in the mental ray rasterizer.

Raytracers shade pixels and rasterizers shade polygons. To get a better raytraced reflection your shading rate needs to be increased (finer polygons) or the rasterizer needs to have more samples to resolve the reflection. Either is an option in Renderman (REYES)

There should be an option to increase the reflection samples for the shader.

#3

mradfo21 is right. With a shading rate of 1 and one ray sample, you dont really get any anti-aliasing in ray traced reflections, you need to crank up your samples to compensate.

#4

Yeah, that was my suggestion. . . .

You have to add the renderman attribute to increase the raytrace samples. I haven’t used the most recent version so not sure where that is. Same place I guess under add renderman attributes.

#5

Thanks guys! I’m gonna give it a shot tonight!

#6

Feel free to post up some results or even a test scene :thumbsup:
(on RmS 3.0.2 here)

#7

ya i can post some of the stuff here i guess. im a little embarassed by it. Its no where near done yet. i’ve only got time to do it on the weekends :frowning:

and vimeo compresses the crap out of the prettyness.

I should say the character is extracted from the game - i didn’t model it. however i’m going to re-model it for the final product. god… all the materials had to be seperated by texturemaps cause he was just one peice of geo.

head:
http://vimeo.com/21301295

body (really needs work/ re-model):
http://vimeo.com/21301260

ya this is what we’re making:

http://vimeo.com/19918333

and ya heres some of the cliff progress from the weekend:

#8

Cranking up the reflection/refraction samples pretty much killed the stills I’m working on right now… render times jumped from ~2 hrs/frame to over 8, and that’s with as much as possible baked and re-used. I lowered the samples back down and quality is acceptable, but it makes me nervous for using blurry reflections in the future when I’d need a lot more samples.

I’m curious if lowering the shading rate (smaller than 1) would be more efficient than upping samples? Maybe if I use a specific shading rate just for the objects that are refracting?

#9

ok so this weekend i’ve done some more work. I really wanted to use renderman (mainly to see why blizzard uses it) and i loved it! However… I took things out of Maya and brought them into max for a test. I hooked up some vray shaders and i got a better image out of the renderer in 140s a frame than rendermans 28 minutes. Adaptive DMC Sampler is amazing.

Now i’m not dissing renderman. the free displacement is such an asset, the SSS is just so flexible. however, as one guy with no renderfarm, i don’t think i can use it. Vray is just giving me much better quality and just such faster rendering (with motion blur and DOF - Vray really doesn’t need too many extra samples in the motion blur when ur using adaptive DMC).

YES, i am not a renderman expert - and doing some LOD stuff via brickmaps looked promising to me. however… For my situation… i just can’t justify NOT using Vray. *sniff

#10

that vray render. yeah it has some noise, but this was 140s vs 28 minutes (ok this is not a fair test. there was a hair system in the renderman one and obviously displacement mapping). but… for me, The results are better (and i think making Vray proxies is easier for personal projects than injecting delayed read archives everywhere).

#11

If you’re raytracing with Renderman, your benefits are less obvious. Renderman’s strengths are obvious when you follow the usual approach (bake, bake, render)

Renderman, like mental ray, is designed for a robust pipeline. As a framework you can build things into it to do your bidding and manipulate the renderer. Baking certain effects will mean Renderman can run with raytracing off and generate fast/accurate frames very quickly and without eating very much memory at all. (Renderman is still king of massive amounts of geometry if you do it right.)

A workflow for a raytracer doesn’t translate well to Renderman-type renderers and you end up with what seems like a poor solution.

Renderman raytracing is best used with a BSDF material and baking the indirect lighting solution.

#12

If you are just hitting geometry then RenderMan isn’t too bad. The problems come when you need to shade the points that you hit - which you normally want to do for reflections. This is because you don’t get the benefits of shading several shading points together - each hit point gets shaded individually.

You can do clever things such as baking the shading into a map (eg ptc brickmap or texture) and just reading it when you hit geometry or doing everything in the pointcloud - such as calling indirectdiffuse(“pointbased”, 1) or gather() in 3delight. Unfortunately you will need a TD to set this up.

Vray or Arnold will definitely give you faster ray tracing right now.

Simon

#13

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