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View Full Version : hdri reflections - fg illumination versus reflection


anthonymcgrath
09-02-2004, 12:20 PM
Reet - I've modelled a skyline (yep.. me too!!) as its plainly obvious I'm never gonna own one :p
I'm currently using final gather to get reflections and I've been trying two methods. Unfortunately I have no pics yet (crappy 56k connection at home) but heres the rundown of the two methods simplified:


method 1 - blinn with reflected colour:
-created blinn
-sampler info plugged into ramp to control reflectivity of blinn
-plugged a .hdr map (pulled off hdri shop homepage..forgot url - sorry) into the reflected colour of me blinn.
-crank up spec whiteness (taking values past 1 to 2 or 2.5) to accentuate reflections

this method allows me to use my own lights in the scene but it floods the colour. Bit lost on this one and curious as to whether this is the method most would use?


method 2 - env ball mapped to sphere:
-created poly sphere
-applied surface shader
-plugged same .hdr map into image. Image plugged into env ball texture.


the second method yields much better reflections. I have no reflection map on my blinn but the same sampler info node plugged to the reflectivity of it. the envball seems to work much nicer than method1 which is strange as I expected it to simply light the scene.


I've had a nebb thru the posts online here but not found alot really on this so I'm just wondering if these are good starting points and which one most bods would prefer. I'm aware theres alot more than just the reflections to work on rendering a car and I plan to add bumps and spec maps and the like later but I'm just wondering what ppl's thoughts are on the reflections.
I'll try n get some pics up tonight but in the meantime - any opinions would be cool.

anthonymcgrath
09-03-2004, 10:09 AM
-heres a piccy of the car so far. I'm using final gathering for illumination mapped to a hemisphere nurb ball surrounding the scene with primary rays turned off. The cars reflectivity is quite high (rangin from 0.2 to 0.6 I think) so its reflecting the nurbsphere.

-Its strange but when I added a reflection map and tried to light it using normal lights (method 1) the reflections seemed to appear 'stenciled' on - the blacks of the .hdr map were quite pronounced and seemed textured on. This 2nd method seems to yield much nicer results and seems right but its just a bit confusing really.

ps - sorry if the black areas seem quite dark (looked oreet on me monitor last night!) :D

-also used the cameras depth of field pass (using that cool DofControl mel script) to get some subtle focus shift. That took bloody ages to render tho - is there no quicker way of getting the same dof effect with mr thats a bit quicker? I found a mr lens effect but it seemed to completely blur out the camera. :shrug:

-lastly, can anyone tell me why the reflections seem quite 'warped' on the corner of the bumper (below the light). They seem to converge to one point.

cheers
ant
newc
uk

http://www.photobucket.com/albums/v90/anthonymcgrath/car_inprogress08.jpg

pappuftp
09-03-2004, 10:17 PM
the pinching u are refering to could be the texture that pinches at the polar points of the sphere u are using to hold the reflection map..

Splin
09-04-2004, 01:54 AM
hey anthonymcgrath
Can you describe your process a little bit closer. I am particulary interetsed of being able to have black background and light the scene myself, like you did it. It is no problem to set up nice fg scene with nice reflections. In Maya 6 there is ibl or if in older version you could make simple spehre and map ur hdr to there. But with that technique I seem not to be able to figure out how to do it. You mentioned that you turned off show primary rays, where?
Thx ;)

anthonymcgrath
09-06-2004, 09:52 AM
My process involves the older method of mapping a nurbsphere with me hdr map (now got it saved as a mel button :D as I'm bone idle!) as opposed to this newer ibl method that I've heard mentioned (dunno what that is tho). The hdr sphere is simply left as is and I amend the specular colour of the cars shader to intensify highlights and wotnot taking the value above 1 to 2 or 2.4 which seemed to work out quite nicely. I'll try n put the scene up when I get a minute with some comparisons on the other method (mapping the cars reflectivity).

Splin
09-06-2004, 11:37 AM
Cool man. The new ibl is nothing more than just making it much easier to setup those hdri lighting domes. It automatically makes virtually infinite large sphere, very easy to apply texture on to it. But whatever I do I can not black out that dome so that I would not see it on rendering, like you have it on your pic. Still see reflections and light with it in a subtle way but keep the dome black. Tho I have few ideas what need to be tested out. That scene would be very cool if you could share it ;)

anthonymcgrath
09-06-2004, 12:38 PM
Well I wouldn't know how to hide the bg dome with the ibl but I do know that if your using the nurbsphere method like me you can simply select the sphere, goto its render stats then turn off primary rays causing it to just light the scene, cast reflections but not actually render.
hope this helps. The reflections on my car are controlled by a ramp plugged into the reflectivity of the car shader. This is then controlled by the sampler info node and a bit of tweaking.

to be honest theres a heap of bods on this site doing car shading and lighting a heapload better than mine. My post is simply to try n get some thoughts on which method people prefer in order to obtain reflections. Unfortunately no-one else has posted really.

I'll post up the scene tonight (cant post up the full car model unfortunately but can stick a proxy in there to give you the idea).

Splin
09-06-2004, 04:00 PM
Ok now I get your idea, ahah. Thats where this hide primary visibility is hidden. Thx man, I'll try it out.
Well yes, everyone seems to know but noone participates :hmm:

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