Rendering Quality Levels?

[dbroad]

A few questions for anyone who renders in Revit frequently.

1) Why is it that the best and medium qualities take far longer but look worse (grainier, dustier) than the draft quality?

2) How do you do a lossless rendering?  The render engine might say the render image is 4.9 mb uncompressed but it results in a 137 Kb file.  That is a lot of compression when exporting to a 12" x 7" print image.  Yet there appears to be no loss control when exporting images to jpg.

3) Do you lose your rendering quality if you don't save it to the project immediately?

4) What is the best resolution to use for print?

5) Why are some materials or material features lost when cloud rendering?  Materials that have cutout maps don't cutout (like cane seat backs).

[Anonymous]

I'll take a stab at a couple of these.  Answers in bold...

1) Why is it that the best and medium qualities take far longer but look worse (grainier, dustier) than the draft quality?

This should not be the case.  There are several other settings that may be conspiring to give you this experience.  Check the default resolution setting on draft renderings you've been doing.  Sometimes I forget to set the rendering setting to a print resolution and not a screen resolution.  Medium Rendering with 150 dpi tends to generate fairly good initial images that can be printed with acceptable quality for most working scenarios.

2) How do you do a lossless rendering?  The render engine might say the render image is 4.9 mb uncompressed but it results in a 137 Kb file.  That is a lot of compression when exporting to a 12" x 7" print image.  Yet there appears to be no loss control when exporting images to jpg.

no idea.

3) Do you lose your rendering quality if you don't save it to the project immediately?

When I first started rendering in Revit I made the mistake of closing the rendering popup window and was disappointed to discover that this also effectively tossed the rendering I had waited so long to generate.   You have to either save the rendering in the project or generate a jpeg for export to keep the work you waited so long to generate before closing the window.  I'm not sure if this is what you are referring to but it sounds suspiciously like a similar challenge to what I encountered early on.

4) What is the best resolution to use for print?

150 dpi tends to get me through but most graphic forums I've scoured in the past seem to recommend 150 dpi for grayscale and 300 dpi for color.  I've found 150 dpi for color does a reasonable job and cuts the number of pixels in the image down to a quarter of what it would be at 300 dpi so this smaller size tends to be my working default.

5) Why are some materials or material features lost when cloud rendering?  Materials that have cutout maps don't cutout (like cane seat backs).

no idea.

[dbroad]

Thanks for your answers.  I think the Revit creators could well do some work to improve this experience.  The switch from using massively parallel graphics card CPU's (NVIDIA Cuda cores) to the computer CPU may have made Revit easier to program and more predictable across computers but crippled the rendering speed except for draft and medium.  Best looks great but for this project, with a 16"x9" image size and 300 DPI, it took 40 hours to render on the desktop.  That is not acceptable performance.  I think the draft renderings look pretty good with the current renderer but with more than a few lights in the scene, the rendering speed of high through best is intolerable.

2)I tried everything I could think of the get medium resolution to show up less grainy than draft. I could tell it was reproducing reflections more accurately but everything looked like spatter paint after the rendering dialog had flagged complete.

3)Yeah, I realized after a few tries that I had to make a decision to save or add to the project as soon as the render was finished, before closing the dialog.

4)I tried to determine the DPI of the output device, which was not in my possession but was unable to.  I ended up employing the rendering cloud because there was no other way within the project timeline to get the renderings out in the quality I needed.  The render cloud had its own issues with loss of materials and with the inability to specify an image size and DPI setting.  The controls as I saw them were only rendering quality(standard - free, final - pay), image size (which had no real meaning anyway since the images were not sized as specified), and image file type.  Rendering speeds in the cloud were acceptable.  In my opinion, if Revit has crippled the rendering speed on the desktop for final renderings,they should offer subscription customers free cloud renderings up to a certain average number per month.

When I get some spare time, I am going to experiment with linking Revit to 3dsMax and find out whether the process can be improved at the desktop level.  This is something I need to be able to teach and deciding how to process a render project for various output devices within a reasonable time is an important matter.

5)Although my final rendering had some material problems in the cane backs (OOTB Table-Dining Round w Chairs Revit family BTW), I was able to work around the problem by remaking the material and storing the cutout image in the project folder rather than in the Autodesk material library.  I suspect there are some file and path string length limits when sending the file to the cloud.  The original name for the cutout image was extremely long and that was inside a deeply nested material library path.  I shortened the name of the cutout image name from Metals.Ornamental Metals.Plate.Mesh.cutout.png to Meshcutout.png and stored it local to the project and the cloud rendered it correctly.  The material was Textile - Bamboo Weave

You can see the end results in the cloud gallery here.

Lastly, I am getting this message when I open the project now:

"Some ACIS objects could not be imported. To import them, use AutoCAD to convert them into polymesh objects and reimport."  

The main problem with diagnostic messages like that is they are useless since they do not identify which objects contain or would have been ACIS  objects. In the AutoCAD drawing triggering the message, a qselect does not list ACIS as an object type.  I suspect that it is choking on the glass shelves I made ias a Revit family and exported using the IFC so I could get context to put the AutoCAD solid trophies on the glass shelves in correct alignment.  But I froze the layer those objects were on so they shouldn't have even been processed by Revit on import.

Thanks again for the response.