Framebuffer (HDR / openEXR)

[Anonymous]

Hello all,

short question: Is there any possibility to access the framebuffer for saving a HDR or openEXR?

Regards,

Pete

[Anonymous]

As you can see here, the framebuffer obviously stores such data and therefore you can adjust the Expose:

www.youtube.com/watch?v=Xtd2iWtn95E&feature=player_detailpage#t=190s

Any help is highly appreciated, thank you!

[jeremytammik]

Dear Peter,

The Revit API currently does not offer any direct access to the framebuffer.

Then only way to go right now to create you own renderings is to traverse the entire database, elaborate each element, retrieving its solids, their faces, their materials, etc., as demonstrated by this all-too-simple sample exporting to OBJ:

http://thebuildingcoder.typepad.com/blog/2012/07/obj-model-exporter-with-transparency-support.html

I hope this helps.

Best regards,

Jeremy

[Anonymous]

Hello Jeremy,

and thanks for answer and your impressive link! But I think it is too much for me, I just want to save HDR or OpenEXR images made in Revit. AFAIK Revit uses mental ray and my above mentioned link shows that Exposure values are already used - so in fact it works already, I just need to save the whole dynamic range of a rendered image.

The question now is if this function is blocked by intention by Autodesk or if there are any plans to give access to?

Kind regards,
Pete

[jeremytammik]

Dear Peter,

I am not ware of any such access. I do not believe the API supports this. I am not a rendering expert either, so I do not know how the HDR or OpenEXR image relates to the Exposure values. Can the image be saved in a file? Can the data you are looking for be extracted from the image file?

Best regards,

Jeremy

[Anonymous]

---

@Anonymous wrote:

[...] I do not know how the HDR or OpenEXR image relates to the Exposure values.

---

Exactly this is the thing all is about, "Exposure" means "HDR".
Explanation: The framebuffer contains ready rendered full High Dynamic Range (HDR, 32-bit per pixel) data. It is not possible (or meaningful) to display all data at the same time. Therefore an Exposure control let the user choose just a part of the full range. Finally this part is displayed and can be saved e.g. to *.jpg, *.bmp, *.png, *.tif (unfortunately only 8-bit per pixel).

What we need is the possibility to save the already available raw High Dynamic Range data (without any modifications by Exposure Control Settings) via API to a *.hdr (or *.exr) file.

A *.hdr ist nothing special, it is a very old standard developed by Radiance developer Greg Ward in 1985 and honestly I don't know any serious software which does not support this format, even freeware tools do so. Because of this I assume that a reference solution like Revit does not offer *.hdr (or *.exr) by accident and not by intention. 🙂 The problem is that for our customers and us purchase of Revit licenses does not come into consideration if this standard format is not supported.

[Anonymous]

Just a short correction, I have mixed up bit per pixel (bpp) and channel. I am sorry for that.

RGB HDR has got 96bpp (32 bits per each RGB channel, each channel is stored in a 4-byte "single precision floating point number")

RBG LDR (e.g. JPG) has got 24bpp (8 bits per each RGB channel)