Proper Reflections

[Andrew West]

I do mostly architectural images and it is often very important to my clients that I get the reflections in the windows to be very accurate.  An example would be a ski area home where I am looking at the house but I need the  mountain  perfectly placed on the living room glass.  Pylon has given me the solution to this by creating a plane outside the view area that has an HDR image of the reflection set to be an emitter material using a value of about 8.  While this does work it also about doubles my render times and leads to a lot of trial and error test renders to get the reflection right.  I have also tried to use an IBL light in my scenes which has great results from a lighting standpoint but I can never get the reflection to show accurately in the glass.  Putting a value other than 1 in the azimuth or altitude crashes the program instantly. I have also tried to put the reflection on in photoshop but that is always tricky since there is a fair amount of transparency in the glass and it leads to some unrealistic results.

 

I am curious to know if anyone has come up with another workable solution to this issue. 

[pylon]

Hi Andrew,

 

To accurately reflect a given environment in the glazing of an architectural structure, obtain a 360 spherical HDRI image of the environment, load it into the Maxwell IBL light type (all channels), use the rotation parameters to position it, and the intensity sliders to balance illumination and reflection. A very high resolution HDRI is recommended for the type of work you are doing, especially at the high resolutions I understand are required for your clients. The reflections will be absolutely correct. I suggest purchasing an existing HDRI from one of the many firms that sell these assets, or comission a photographer who specializes in spherical HDRI panoramas to photograph an environment typical of your client's site. A few excellent HDRIs would probably save you a lot of time and effort.

 

To artistically reflect a standard image in glass, use the image-mapped emitter plane technique. This should not require much time to adjust; if you just show the glass and emitter plane layers,  you should be able to adjust the reflections in real time in Fire at an adequate resolution. Alternately, use the Custom Alphas feature. For each plane of the facade, assign all glazing on the plane to a named layer, then create a Custom Alpha for each glazing plane layer. Then use the automatically generated masks to composite your reflections in photoshop.

 

 

Putting a value other than 1 in the azimuth or altitude crashes the program instantly.

I just tested this, and adjusting the rotation and/or altitude does not crash formZ here. If you have a file where this occurs, please send it, along with information about the version of Maxwell you are using, OS, etc.

[Andrew West]

I have never used the custom alpha technique.  I will try that first. 

It is often impossible for me to get high quality HDRI spherical maps of the environment I need.  My clients are very cost sensitive and I struggle to get them to even pay for a photographer to go out to a site.  These projects are also spread all over the country so site visits are out of the question.  As a result I often get camera phone shots that are pretty awful. 

When I tried to load an HDRI image in as an IBL light I find it curious that the reflection is quite blurred.  Is there a way to adjust that?  The image was fairly high res.  This light also dramatically increased my render time. 

 

[pylon]

The ability to make as may alphas as you want, based on individual materials, objects, and layers, as well as collections of these, is a very powerful feature in Maxwell for formZ that I've used to solve many tricky compositing problems.

 

Not sure about the HDRI bluriness you describe. It could be that the HDRI was not a spherical panorama, was too low resolution in relation to your rendered image size, was reflecting off low-poly objects with smooth shading enabled, or some combination thereof. If you send a stripped down scene, I can troubleshoot it and let you know.