Wireframe, Measurement and Collaboration

Michael Kaplan, Director of Engineering for Acrobat 3D, clarified some of the issues I raised in my First Impressions. I mentioned that “many proprietary formats cannot be imported as NURBS”. I stand corrected. Indeed they can, but I think I need to clarify what led to the confusion.

I created a simple cylinder in SolidWorks and saved it to a part file which I then imported into Acrobat. Acrobat warned me that the document would contain precise B-rep surfaces and that I should use its security mechanism to control access of the resulting PDF file. Surely enough the model came in shaded like a solid. But I know that a shaded model is actually a bunch of colored triangles, the render mesh. I wanted to see the actual NURBS data, more specifically, the smooth edge curves. So I changed the mode to wireframe. I was surprised to get the same bunch of triangles in the wireframe as well. No smooth curves, just dumb triangles.

What followed was a good twenty minutes of my time spent in tweaking various import options to find the “precise B-rep surfaces” that Acrobat had warned me about. No joy. No matter what I tried I couldn’t get Acrobat to show me the two smooth circles that made up the cylinder.

I decided that I must be doing something wrong because I could not believe that wireframe could mean the render mesh. So I opened Adobe’s demo PDF file, a striking product brochure of a gas turbine engine with animation and all. I switched to wireframe and got the same render mesh.

I am now assuming that Adobe’s interpretation of the word “wireframe” means the render mesh that is used to display the model as a solid, something quite different from what we in the CAD industry know it to be. Like Ralph Grabowski commented to my earlier post, maybe “Adobe does not fully understand the CAD market yet and its rather particular demands”.

A little shaken, I then decided to verify whether Acrobat really had access to the B-rep data. I exported the cylinder to a neutral 3d format (IGES) and got it back into SolidWorks. Sure enough, it came in as a B-rep. So the PDF file indeed has the B-rep information, just that Acrobat is not showing it. At least I could not find a way to see it. All I see is a bunch of stupid triangles which make the model look like one big mess of criss crossing lines.

Another thing which struck me was Acrobat’s measurement tool. Everyone knows that engineers are paranoid about dimensions and tolerances. They talk about microns as if they were miles. I am not sure they are going to be happy when they come to know that Acrobat’s measurements are based on the same render mesh that they call “wireframe”. If I want to measure the distance between a point and the mid point of an edge curve, I have to hope that the render mesh has a vertex at the mid point of the edge curve in question and then successfully find that vertex in the crazy maze of vertices of the “wireframe”.

Acrobat has something called “3D Conversion Settings”, which are essentially preset file import options which users can select depending on their need. One such setting, called “Collaboration”, caught my attention. The description for this setting is: The Collaboration conversion settings are recommended for 3D-based collaboration workflows. Using this preset will increase the precision of the measurement tool.

Here “increase the precision” essentially means that the “surface triangulation” is set to high, which means that you will get a larger render mesh to take measurements from thereby increasing your chance of taking wrong measurements, thereby defeating the very purpose of collaboration.

I am not quite sure what Adobe’s view of collaboration is. You just cannot give an engineer down in manufacturing a mesh (however fine and hence unmanageable it may be) and expect him to “collaborate” effectively with an engineer in the design department. He needs to know distances, angles, surface curvature and continuity, etc. precisely, from a NURBS model, not based on some stupid render mesh. A 3D model is not any ordinary document like a purchase order, and I feel Adobe needs to realize that.

Probably people down in marketing will be excited to have access to a 3D model, something which was limited to engineers. Acrobat also has a mode called “Shaded Illustration” which may be useful to techical artists. A 3D model will surely look great in a product brochure, where a customer will be able to rotate, zoom, pan and even section the model. Their 3D PDF demo of a gas turbine engine brochure is truly amazing. I am assuming that when Adobe says collaboration they mean collaboration between the technical team on the one hand and the non-technical guys on the other. I can see no meaningful technical collaboration with this version of Acrobat.

But this one takes the cake. There is no “zoom window”. No, wait. Let me rephrase that. I could not find how to zoom into a window of the drawing view. Come on. Any decent 3D application has an option to zoom into a window. You surely do not expect users to zoom into the drawing along the line of sight, then pan to change the line of sight, zoom a little more, pan a little more, and so on, till they finally reach the window they want to zoom to. Interestingly, there is a zoom window feature, but it works only for the text portion of the PDF file. For the 3D portions it acts like a zoom in/out along the line of sight.

A lot has been done and a lot needs to be done. I hope someone at Adobe takes this as constructive criticizm and acts on it. They simply have to get the words “wireframe”, “measurement” and “collaboration” right. It is vital for Acrobat 3D 8 to be a success.

Update (10-Mar-2007)

Michael Kaplan clarified in a comment to another post that Zoom Window does exist. For a 3D part of a PDF file, you need to click-drag the zoom window using the right mouse button, not the left. This is because the left mouse is used to zoom in/out. For the text parts you have to use the left mouse button to select the zoom window and zoom in/out. Pretty confusing. I feel Adobe should find a consistent way to navigate through the entire PDF file.