Fake lighting tests

[loramel]

Inspired by article about product renders in one of the last blenderart magazines by cekuhnen I decided to try it myself.

I soon found out, that I am not quite satisfied by the workflow and principles involved and started to expand and change the workflow and setup.

I use this thread as a place to test various aspects of this technique and discover what works and what not.

The basic idea is to have a lightprobe image in angular lightprobe format and map this to the material to fake reflections.

There are several good HDR images of studio setups available, but I want to be able to generate my own.

For this I use luxrender to generate a high quality correctly lit lightprobe map (using its environment camera setting). The very same scene used in lux, is used in the blender internal scene.

Having no real experience with good/correct studio setups I started with a very simple setup



The squares are simple light emitting planes acting as area lights in luxrender. The camera in the middle is the environment camera and sits on the spot where the object will be placed.

The next idea is to use as few lights as possible in blender. My goal is to get rid of any lamps alltogether and just use AAO and the lightprobe map(s), but I not there yet.

Right now I use AAO and hemilights where the area lights are to lihgt the scene.

Using the previously generated lightprobe with this setup and with a simple palette object I get the first result:



( ignore the jagged lines please. the forum seems to mess with the images displayed)

This render actually took 1.5 sec on my quadcore machine, quite suitable for an animation.

And here is a first animation test with the same settings.

I will further explore the various settings annd post them here.
If something useful comes out of this I may post a small tutorial together.on my site.

[Meta-Androcto]

very cool work.
I'll watch for updates.

[Atom]

Nice explanation. I wondered how some of those HDRi files were created.

So inside LuxBlend you have changed the camera from the default of perspective to "environment"? This renders 360 degrees around the scene as a single frame, right?

But does this actually make it an angular map or a spherical map? Are spherical maps the same a Lux's latlong mapping?

Cameras are one of the next things on my list to play round with in Lux.

[Ace Dragon]

One of the GSoC projects expands on the IBL patch submitted by Broken and supposedly allows very powerful control over a light environment in the Blender Internal renderer complete with light paint, I think there's a wiki page on how it works.

[loramel]

Originally Posted by Atom Nice explanation. I wondered how some of those HDRi files were created. So inside LuxBlend you have changed the camera from the default of perspective to "environment"? This renders 360 degrees around the scene as a single frame, right? But does this actually make it an angular map or a spherical map? Are spherical maps the same a Lux's latlong mapping?

The studio map you have attached is one of those I mentioned in my original post. It seems rendered too.

Spherical maps are not latlong maps, neither are angular maps. Angular maps are typically used with lightprobes and look like this ( a very crude light probe I created myself for my forest scene )




The output of lux's environment camera is a latlong map as are the maps from the HDR studio pack. This format is immediatey usable inside blender with sphere mapping and using the reflection coordinates, as it is done in my tests.

I will explain the steps in a liitle more detail in a following post to highlight the necessary mapping modes.

[loramel]

Originally Posted by Cyborg Dragon One of the GSoC projects expands on the IBL patch submitted by Broken and supposedly allows very powerful control over a light environment in the Blender Internal renderer complete with light paint, I think there's a wiki page on how it works.

Yes, I watch this development with great interest. But as of now I will have to use what's available and see what can be done with it.

[loramel]

I tried to see how varying the reflection intensity influences the material property.
Furthermore I used the studio environment map in different blurred versions to simulate a more glossy appearance.

Here are 3 of the maps I used



Here are also set up a simple material node to to able to extract the reflection property and put it into a single material node for easier reuse.



The actual mapping is done the following way



I found out that it's quite important to use hdr images as input texture, as otherwise the dynamic range gets lost and the reflections just look dull. That gave me the next headache trying to blur an exr image with the tools at hand when using linux. In the end I used the only tool available for that task - blender.

The next step will be to try to use the texture node editor to do the actual blurring and have everything in one place and easily accessible for tweaking, thus simplifying the workflow.

See here for a matrix showing the different settings for blurring (0,8,32,128,256) and reflection intensity (0.01, 0.05, 0.1, 0.25)



And here some higher res picks from the matrix for a better impression:

slightly blurred with 8 for a small glossy effect:



more blurred with 32 for a more visible glossy effect:



and even more blurred with 128 for a quite heavy glossy effect:




And see here for a video created with an environment map with a blur factor of 256.

[Atom]

Nice work, I like the slightly blurred with medium reflection intensity.

A question, however. I tried out the environment camera in Lux and got nothing but a black scene with 0% light efficiency. I am using v0.6RC3. What is the trick to making the environment camera actually work? I am using the default Blender cube scene. I have removed the standard light and replaced it with a mesh plane that I have assigned the light material to. I have tried rendering with the enivironment lighting on and off. Still, all I get is a black scene with 0% efficiecny.

[loramel]

Originally Posted by Atom ... I tried out the environment camera in Lux and got nothing but a black scene with 0% light efficiency. ...

I guess you're using bidir for your integrator. Lux RC3 has a bug, where the bidirectional integrator does not work with environmental cameras. In RC4 this issue is solved ... almost .

As it seems the 64bit version crashes. And of course I am using a 64bit system, so for the moment I either use path tracing or just plain direct lighting.

[Atom]

Thanks for the tip. Selecting a different integrator does work!

It does look like bidirectional does not work in RC3. I tried it in RC4 and RC4 crashed, it still seems kind of buggy. I was hoping RC4 would be a bit faster with all the qbvh work being done, but my renders still seem to drag...

[loramel]

I tested a little more ...

... and ran into the first setbacks.

First I tried to use the texture node editor to control the blurring with it, thus eliminating the need for an extra preprocessing step.
I soon noticed 2 things which prevents this approach:
- the texture node editor has no blur operation
- the node editor does some strange things to image maps.

I will explain:
Using a normal image texture I get the following result in the material node editor:



Now I set up a very simple texture using the node editor, essentially just passing the image through it without any (obvious) modifications like here



But when I use this texture I get the following (wrong) result:



It just seems, that blender is messing with the mapping and also extends the image in a way, which I do not understand. I will try to make a simple example and file a bug report.

The next idea was to see if I am able to use the environment maps in some way to even get rid of any lights. Well, I gave up on this and must resort to the technique of placing lights (hemi or shadowless spotlights) at the location of the real lights. This is no real problem with self generated maps, but may cause additionally headaches when using externally provided maps.

After this I played around with mixing differently blurred environment maps on the same material to fake inhomogenous surface properties. I also added normal maps and created a very dirty (corroded) material



This result gives hope that one can use this technique for more than just clean product shots.

See here for a video which better shows how the dirt works out.

The next steps will be to play with animated objects and animated cameras, where I fear the next problems will arise.

[Atom]

I am just wondering here, is the Blender node editor fully 32 bit compliant?

From what I understand, you are creating an EXR file (which contains 32 bit color) in Lux, then you are feeding that back into Blender's node system. So the assumption you seem to be making is that Blender's node system is not going to downgrade your 32 bit color image at all. Correct? Even your simple example of going from an input to an ouput shows loss in quality. Maybe that is why?

[loramel]

Originally Posted by Atom I am just wondering here, is the Blender node editor fully 32 bit compliant? From what I understand, you are creating an EXR file (which contains 32 bit color) in Lux, then you are feeding that back into Blender's node system. So the assumption you seem to be making is that Blender's node system is not going to downgrade your 32 bit color image at all. Correct? Even your simple example of going from an input to an ouput shows loss in quality. Maybe that is why?

Blender is handling all internal image data as 32bit float, so from this perspective there should be no real loss involved. The loss in quality is just a display problem. I think blender is optimizing the display, but maybe something more is happening. What concerns me more is that the texture node system messes with the mapping.

[Bliz]

If you haven't already, you should take a look at Zordon's WIP thread for his 2009 F1 contest entry.

http://blenderartists.org/forum/showthread.php?t=155120

He is using the same product visualisation technique from issue 21 of blenderart mag and some of his test renders look really nice.

[loramel]

Originally Posted by Bliz If you haven't already, you should take a look at Zordon's WIP thread for his 2009 F1 contest entry. http://blenderartists.org/forum/showthread.php?t=155120 He is using the same product visualisation technique from issue 21 of blenderart mag and some of his test renders look really nice.

I didn't know that he used the same technique, but after reading through the thread I think it was just for previz.

The 'problem' with cekuhnen's setup is that its using a different mapping (normal coordinates) and relies on self generated env. maps. This setup gives a fake result (even more fake than mine) as it just resembles the light setup.

My approach is to have a correct reflection and be able to either create my own map or use existing latlong studio maps.

[loramel]

I found out, why the texture created with the texture node system does not work.

As it seems the mapping modes (flat, cube, tube, sphere) are ignored when using texture nodes. Only the flat mode is used, thus destroying my setup

Well, I did some tests with a model more suitable for studio lighting and fetched a car model from the blender respository. The model itself is by sebi.

I did some tests with a more elaborated studio setup and finally rendered the following map with lux.



The car model isn't the best and has not good continous smooth surfaces as there are with real cars, but one can still see how the technique works.

Here are 2 shots from different angles



And here is a short animation showing how the reflection works.

[Atom]

That is a nice look.

Any chance of you posting the BLEND file? I'd like to try out your setup.

[loramel]

I did some tests to examine how the position of the camera or the object influences the outcome, which is especially important in regard to animation.

As it seems - and which was to be expected - as soon as you start to move the camera from its origin or start to move the object away from its origin (point from where the env map here was taken) you get more and more incorrect lighting reflections.

See here an image where the real reflections are overlayed in green to indicate the errors to the mapping technique.

First where the camera position is in its origin


Then the camera is moved in an arc around the z-axis of he sphere ~60 degees


And finally the camera looks down to the sphere above its original position


You can see quite clearly where the mirrored and mapped reflections diverge.

So this technique is quite ok for stills but of limited use for animations, which involve a wide area of movement.

I think I will conclude my tests with this.

For the interested get the blend file from here. It includes the setup for the lux rendering as well as the palette and car models and of course the fake lighting material.