[Tan Boon Meng]

Hi All, or to anyone familiar with car lighting.

Before i begins, just a bit infomation. Im using Lightwave 3D and with the latest Maxwell plugin installed.
Is about how to use HDRI to lid up a car properly matching a backplate. I did up 2 renders based on 2 different setups (A & B featured below) but both neither gives the right feel.

Note: Both are not final renders so ignore the wrong reflections or windows without highlights etc and no post works yet, but do note on the look and feel shading that were produced on this 2 different setups.


Render A.

This is how the scene was setup.



Image A (actual setup): A HDRI was used in the IBL's reflections, refractions and illumination (All U & V scale 1.0) and each individual of them has their intensity adjusted differently.
Image B & C (tried adjusting HDRI but doesn't work): Environment need to be resized to fit the backplate im going to use so i resized the HDRI used in the IBL. But resizing dont seems to work or i have not done it right? If i reduced the U & V scale down, the result is image B where everything were gone including the road. If i enlarged the U & V scale up, the result is image C where everthing is repeating, images stacking up on top of each other. So both dont works for me. The HDRI cant even be rotated to match the backplate so i have to parent every objects and my camera to a null and rotate the null to an angle i want matching the sun's position.

This was what rendered.



For this setup,

Pros:
1) Shading matches close to the backplate i am using, more natural compare to render B (shown later)

Cons:
1) HDRI cannot be adjusted (size or rotation) freely thus reflection is out.




Render B.

This is how the scene was setup.



Image D (actual setup): Same as setup A but HDRI was used in the IBL's illumination only (U & V scale 1.0) and an emitter sphere was added with the same HDRI used in IBL, mapped onto it. It served as reflections which can be resized and rotated freely and this sphere is unseen by camera so it will not be rendered out.

This was what rendered.



For this setup,

Pros:
1) Emitter sphere can be controlled freely, thus reflections can be in any positions and scale i want.

Cons:
1) Shading is out. It seems like the car is well lid on all side. Kind of unnatural compare to render A (mentioned earlier above)




So my questions are,

1) What have i done wrong and what else can i do to make it better? (beside post works)
2) Why cant the HDRI in IBL be sized properly or rotated?


Regards.

[Mihai]

You shouldn't scale the HDR map since it's made to map perfectly onto a virtual sphere, so it won't map properly anymore if you scale it in any direction. All channels of the IBL should match in rotation, or the reflections won't match. I don't know if you have the Offset parameters in the LW plugin? That allows you to rotate the IBL, you have these controls in Studio.

[Tan Boon Meng]

Sorry for late reply, was holiday over here and weekend family day. : )

Hi Mihai,

I thought how it works is to scale it accordingly to how the highlights go (depends on the backplates) and the reflections reflect on the car, so i was wrong. But for Render A that was shown earlier, the image scale in IBL was 1.0 but the reflections on the side of the car is wrong, is too huge because when i place the car into the virtual sphere, the environment looks too big thus the car is too small, making the car bigger wont help too as the environment stays to a fixed scale, so how should i tackle this problem? Anyway I did use the same settings throughout the IBL channels if one of it is changed, that is if the illumination is changed i will apply it to the reflection and refraction settings as well. Yes there is offset parameters in the LW plugin but it repeats the image when is scaled causing repeated reflections, unlike mapping onto a sphere when is scaled down or up the image will not repeats but scale accordingly because is object scaling.

I actually likes the scale 1.0 illuminating the car but the reflection is too big. Scaling down the image in the IBL reflection channel repeats the image and will make it worst. So i was wondering how any better ways to make both side works. Illuminating properly against backplate and having the reflections reflect in the right scale.

Regards.