3D Rendering Tips #2 – Building the 3D model

alpine_2aHere I am going to be talking about building a 3D CAD model of the exterior of a building. Typically I will receive AutoCAD drawings of the building. I use these plans and elevations as reference drawings to build the 3D computer model.

Tip: Don’t put in more detail than needed.

If you won’t be able to see it, there is no need to model it. For the exterior of a building this means that you should not need to model anything smaller than one inch. If it is smaller than 2 inches you probably don’t need to show it. Think of it as if you were building a 1/8″=1′-0″ cardboard model.


I find it best to create a new empty drawing to build my 3D model in. I can copy what I need from a drawing that I receive and past into the new drawing. I keep the original drawings for reference. I take the floor plan that I receive and remove everything that I don’t need, like dimensions, notes and hatch patterns. Everything that is left I move to a single layer and color. The cardboard model is a good analogy. You are going to be building your model on top of this plan. Do the same thing for each of the other floors and the roof plan if you have one (these are very useful). With each floor plan on a separate layer and a different color, place them on top of each other. Move them vertically to their relative distance apart. If many of the floors are the same, at least on the outside, you only need a single copy.

Tip: Move the floor plan so that the approximate center of the plan is at 0,0.

This will make your life easier when you import the 3D model into MAX, trust me.


Put each of the elevations on its own layer. Rotate them around until they are vertical and aligned with the plan. It’s like building a house with playing cards. Here is where you are likely to discover that they are not all drawn perfectly and everything may not line up precisely. The better they are drawn, the easier your job will be from here. You will be using these as reference while building the model.


Tip: Save often.

This is always good advice but it is even more important when working on a complicated 3D model. I recommend saving each time you finish a portion. Or whenever you have done something that you are proud of, save. That way you can return to that point if you later screw things up.

Depending on the complexity of the building there are a lot of ways to proceed from this point. If it is a complex building shape, I sometimes find it useful to first draw a 3D outline of the building just using lines. I’ll put this on a layer called outline. As a mater of fact, anytime you are having trouble deciding how to model any part of the building, you can always draw a 3D outline with lines and then just place surfaces on this wire frame by sapping to the ends of the lines.

That’s all for now.

3D Rendering Tips #1 – Colors and Layers

I do a lot of 3D computer generated architectural renderings. I’ll attempt to describe, in a series of posts, the process I use.

I will typically receive AutoCAD drawings from my client. I import these into Arris, or sometimes into Sketchup, and create my 3D model there. I then export this 3D model back into AutoCAD. I import this into 3D Studio Max where I apply materials and generate photo-realistic renderings. I sometimes then use Paranesi to insert people and tress, or modify the lighting. I will then typically open these into Photoshop where I add finishing touches before sending the finished rendering to my client. I will be posting a series of 3D Rendering Tips to try and explain this process. This is my first post on this subject.

I work in Arris to build my 3D models. However, most of what I do can be done in AutoCAD, or Sketchup, or almost any 3D CAD program. I will use AutoCAD terminology for all of these tips.

When I build a 3D architectural model the goal is to end up with an AutoCAD drawing that contains each different material or color on a separate layer. So one of the first things to do is start a list of what materials or colors will be used in the model and assign a color number to each of them. I try to keep the number of different colors used to a minimum. I don’t like to have more than about 16 different colors.

Tip: Keep this list handy, you will be referring to it often.

I work with two different drawings for the model. The first one I make is used for building and modifying the model. We will call this the master drawing. I work in this drawing 98% of the time. When finished, I save the master drawing with a different name and edit it to become the drawing I send to the client, or to import into Autodesk 3D Studio MAX. We will call this the final drawing. The reason for two different drawings has to do with colors and layers.


Tip: When working on a 3D model, use lots of layers.

This lets you work on small sections at a time and facilitates edits. Don’t try to use any layer standards, just add a layer whenever you start to work on another part of the building. For example, you should add a new layer to work on before you model the first window. Perhaps name it window1. The name of the layer doesn’t really matter.

Leave the default color for all layers set to white. Don’t use “layer color” for the colors you use to build your model. Explicitly select the color number for each thing you build from your list of color numbers you have assigned to the materials. For your window, you may have assigned color number 1 to window frames and color number 2 to glass. At this stage the actual color you use doesn’t really mater. I tend to use colors where I can easily distinguish one from the other. Red for brick, blue for glass, yellow for trim, etc.  Don’t hesitate to use as many different colors on one layer as you need. We will cover some tips for building the model later. Then the model is finished, save it with another name. This new drawing you make will be your final drawing.


I keep the master drawing around so it will be easer to make revisions later. What I do with this copy of the master drawing is turn it into the drawing with each color on its own layer.

First add one layer for each different color you have used in the model and name them according to what the color represents. For example you will normally have a roof layer, a glass layer, a brick layer, etc. Then select everything that is color number 1 and change the layer these entities are on to the layer you created for color 1 entities. You can use the FILTER command to select all entities that are of a particular color. Then you can use the CHPROP command and select “previous” to change them to the desired layer. Repeat this for each different color that you used. Then delete all of the original layers. You will then have a drawing that contains one layer, properly named, for each material. You will also have layer 0 because AutoCAD requires you to have a layer 0, with nothing on it. Now you can change all entities to color by layer, and change the default color for each layer to a color that looks a little more like the building colors.

This is a lot of work and very repetitive. You may want to write an AutoLISP program or two to make this last part go a little faster. Especially when you consider that this final drawing will be difficult to edit. You will want to return to the master drawing to make changes and then repeat these steps to make a new final drawing after each revision. But AutoLISP programming tips are beyond the scope of these 3D tips.

Having each material on its own layer makes applying materials in 3D Studio MAX go very smoothly. But more on that later.