noob at HDRI rendering :S

[agrmrs]

hi friends .....this is my frist time doing an hdri render .......i applied the hdri to environment shader .......but there are some blotches in my render .....when i increase the FG rays it gets highlight more and more below u can see them and my settings too ..... ur help would be much appreciated thanx

[owei]

hi!

At least you will have to play with the two parameters given. 64 for the rays is pretty low. Try something beginning with 200 or something like that.
Increase the number of points until you get clean results. Take a look at the manual:
Number of Rays: "Defines how many rays are fired from each pixel to calculate the indirect illumination. Use low values to tweak the effect (around 10-30) and increase for the final render (>100)."
Points:"The minimum number of precomputed final gathering points that are used for interpolation of the indirect illumination."

cheers,
oliver

[Maximus]

those blochy arent made by FG low rays, 64 are enough, i've rendered hq images with 32 and an HDRI.
The problem here is the HDRI itself, that kitchen_probe.
It has too many bright peeks that cause Mental Ray to reacts like that, you should always use a slightly blurred hdri for the Final Gather computation, and a normal one for reflections.

Avoid to use 1 hdri for all purpose, its counter productive, plus if your HDRI is big size in terms of mb, your render time will go to the roof.
Check out sIBL GUI for softimage and how it works, i've dig into this for quite a bit and came up with a node that i usually use for my stuff, you can check the thread here.

http://www.xsibase.com/forum/index.php? ... #msg270866

Anyway i have the same HDRI and i've done a blurred one for the illumination and it works fine, as i said that HDRI is the reason of the problem, HDRI shouldnt have those bright peeks and strong values into the illumination.

also remove the filter size, this is set to 1 by default when it should be 0, this cause a lot of problems later on, use always 0, and increase it if you having problem (lowering it always fixed many problems as far as i tested, so i never use this filter ever).

[agrmrs]

thanx a lot for both of u i'm checking these links ..thanx again will update soon

[owei]

@Maximus
...yes you are right. But increasing the rays and the point will end up in non-blotchy image without blurring anything. I´ve just stated, that 64 rays is too low for this constellation and it definitely is considering all what you said about the peaks in the hdri. The fg rays are simply not enough to compute the fg points without blotches. Blurring the hdri is a nice workaround to achieve lower fg settings and short render times but might not always be the best way.

my 2 cents
oliver

[Rork]

The basic rule for HDRI rendering is to use a small blurred version of the HDRI for FG lighting, and use the original HDRI for reflections.
The way to implement this is to use a raytype node to split the different HDRI's up for camera, FG, reflection etc.

That is also the way sIBL is working. That way, especially with animation, you don't have a lot of issues with stuff like this.

rob

[agrmrs]

hi guyz me came up with a render according to ur advices worked pretty well than before ...... me used mia exposure simple shader too give u crits cand comments to optimize ma render thanx a lot

[shushens]

I don't think you need exposure control here. What Simple Tone Mapping is doing, you can also do in Photoshop later on.

Now you can give the chair some good materials. Steel and plastic both heavily rely on reflection maps, so it will show off the HDRI.

To easily make steel, use mia_material with IoR 25, BRDF checked (not checking is fine but this reduces render time slightly, at least in my system), reflectivity full. If you get very cool looking reflections, HDRI has done it's job ;)

[agrmrs]

thanx shushens gonna try it.....will post the screens soon

[agrmrs]

hi guyz here's the result when i'm using hdri without tweaking any setting .....but the render is too dark ........ i'm using a normal lambert material .... even i increased hdri exporsure or intensity,there were still very dark areas .....before adding exact materials ( chorme etc ) i'm trying to do kinda soft clay render ........ but the render is too dark ur help will be highly appreciate thanx

[Maximus]

you have probably a low tonemapping cd/m2 factor, post a screen of that settings, your simple tonemapping operator, also check ISO, check f-stop, there are a bit of parameters that comes into play

[agrmrs]

thanx a lot maximus me turned on gamma settings in render regions ...... now it shows the real color me textured some parts and also used architectural materials to make them ....... below u can see the screen

i need to make kinda rubber material for the chair knobs (at the bottom of the legs ) with a little bit of specular and roughness ......i tried it to do using architectural material but couldn't find where to increase specular and roughness can some one tell me how to achieve that .....thanx a lot

[Rork]

Maybe you already know this, but I made a set of presets for the Arch. material.
Just follow the link in the footer.

rob

[agrmrs]

Maybe you already know this, but I made a set of presets for the Arch. material.
Just follow the link in the footer.

rob

thanx a lot mate just gonna try it i used blin shader for this and worked fine ........ me put a lightbox ( with mia portal light shader ) behind the chair to give a nice rear light setup ...... when i render it xsi gives me an error as u can see below ...... ur help will be much appreciate

error



render so far

[Rork]

It says just that, you need to set the light to visible in the PPG for the portal light to be active. ;)

[agrmrs]

It says just that, you need to set the light to visible in the PPG for the portal light to be active. ;)

ahh worked it .....thanx mate