Tips and tricks for architectural rendering

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tips and tricks for architectural rendering
By zsolt.


modeling.
no N-Gons, what now? .

One limitation that comes up in rendering architecture is: Blender lacks N-Gons, y, e.: Polygons with more than thre or four sides. While quads are great for Many types of modeling - Allowing clean subdivisions, loop modeling, large, complex flat surfaces are easier todo handle as one single polygon instead of dozens of small triangles/quadrilateral. For example, se the wall on the first image. The outline looks harmless enough, its the facade of a venetian building, with place for one dor and several Windows. This could be solved with one Concave (i, e.: has holes in it), or several Convex N-Gons, but in Blender we ned the following, very ugly setup of 113 Faces (figure2). Not only ugly, but it is now hard todo continúe any sort of modeling on it, like subdivisión, adding more detail, beveling some corners. Solution?
1. F-gons.

F-gons are faq N-Gons. Basically, you select the Faces you want, hit f and select make f-Gon. From now Blender Will represent it as one face in face select mode. It is now easier todo select the whole wall. However, this is just a cosmetic change, the above mentioned modeling problems continúe todo exist. Therefore the one really god use for it is at the very end of the modeling process.



2. Go modular.

If youre like me, and prefer vertex-pushing as the only true modeling technique, you can try a modular modeling approach. Basically, divide the building into sections, both in height and width, along strategic lines. Ie: if the Windows are spaced one every two meters, then one section would be two meters wide, and would contain one window. The height of the sections can be one flor (or smaller if there is more detail). Se figure 3. Notice not only that the model is cleaner, but each and every window can be separated and taken out, and another one put into place, without disturbing the rest of the Mesh.
quick tip: modeling one section: add a plane, and move the corners todo the proper positions (always, always use Snap todo Grid, or type exact numbers by hand). In the same Mesh, add the outlines of the holes, inside the plane. Select all, and hit shift-f, fill. This creates the necessary triangles. Now hit alt-f: beauty fill, which Will rearrange the triangles todo minimize extremely long Polygons. Note: you might ned todo hit alt-f several times one After another for the optimum result. As a final step, convert as Many triangles todo quads as posible with select Faces => alt-j. Repeat for all sections.


This type of modularity is especially useful for large buildings, you can pre-model several window, dor types, and then Simply duplicate them (shift-d) and move them around. The exact sizes and the Snap todo grid option ensure they Will match up at the Edges. When done with the Mesh, remove the duplicates (in the w-key menú). And remember todo extrude the wall todo the proper width.


Many other types of models can benefit from modular modeling, which is básically: interchangeable Mesh parts, all with given outside dimensions so they can be easily joined or separated.
3. Use curves.

Curves are a los a modelers best friend. For the wall sen above, the contours can a los be modeled with Bézier curves. Just add a Bézier circle, set the sides straight (v key), and then move the vértices around todo the proper places. Add new curves inside the same object for the holes you ned. You Will se that Blender automátically fills in the shape, and knows which part is solid, and where the holes are. In the edit buttons, curve and surface panel, the Defresolu button determines how Many straight segments Will make up one curve segment. The higher the number, the smoother the curve Will look when rendered. This is one advantage of using curves: the resolution can be changed, in a Mesh model, you are stuk with what you first modeled.


Dont forget todo set a width for the wall. The extrude button sets the width of the extrusión in both directions. Ie: a value of 1.0 Will extrude the curve by 1 blenderunit (bu) both ways, which makes a 20 centímetros thik wall if your scale is 10 bu = 1 meter, the scale i usually use.

Note: Bézier curves are 3rd (some programas a los use 5th or 7th) order functions. This means that no matter how Many control points you have or how well their handles are placed, a Bézier curve Will never be a perfecto circle. Youll probably not notice it on a rendering, for archi-Viz Bézier is just fine. But if real precisión is required, then use Nurbs curves, or a Mesh with Many vértices.

You can a los bevel the Edges a bit, no wall has a perfecto, Sharp edge. The bevel depth button sets the width of the bevel, this is added on top of the extrusión. So todo have the same 20 centímetros wall with 0.5 centímetros bevels you ned extrude = 0.95 and bevel depth = 0.05. Set the bevresolution todo 2 or 3, that is usually enough.
beveled curves: curves can a los be used for other architectural details, like railings, rails, gutters, fillets, trims, window and dor frames, pipes, wires, ropes, and anything else that is long and has a constant cross-section. This neds two curves: one that gives the length or Path of the object (aka directrix, rail curve, Path curve, etc.) the other is the cross-section (aka generating curve). The cross-section has todo be added todo the first curve as a bevob (bevel object). Figure 6 shows some of the objects that were modeled with beveled curves in this venetian scene. The curve at the lower left is in Edit Mode, you can se it is a simple square. Its complex cross section is the Bézier curve object called trim1.


Note1: watch the defresolution of all the curves you use in the scene. The more complex trims in this picture have as Many as 20 Bézier curve segments, which multiplied with the default resolution value of 6 is todo high, and can bost your render times th rouge the rof. It Will not make a diference in quality if you reduce this number todo 3 for smaller objects. On the other hand, the Path curves might ned a higher value if it has large Smooth curves in it.

Note2: when the model is done, it can be converted todo a Mesh (alt-c) for further detail work, like bevels, some random noise, etc. Remember this is a one bien conversión. Also: this might a los be neded for other outside renderers if the curve objects arent exported well with the export script(s).
texturing.
programa tip: Acme online.

This is a very useful Little programa. It can be used for one thing only, but at that, it is the best: making brik textures. Instead of the usual perfecto brik textures, which Will Scream CG, at you from an architectural rendering, this programa can make large, non-repeating brik wall textures, with the bricks having slightly diferent shapes, the montar ozing out from them and a bit uneven, y, e.: realistic.

You can choose from about one hundred brik types, all with diferent colors and surface textures, plus Many montar colors. Coursing types (how the bricks are stacked): stack, running or third. When you have selected everything, it Will render the texture for you. The size can be defined by the user, some very high-res textures i use are 60 bricks wide by 20 high (resolution of 15488 * 1680 píxeles). This Will cover large Walls without the viewer seing any repetition in the texture, since the programa places slightly diferent bricks - Of the given type - Randomly.

This is not all though, as you can replace a whole row or just one brik with another type of brick. This allows you todo draw or Paint complex bricks setups, including decorative tiles, adding cornerestones and Header estones, etc.

The programa is free todo use. When you want todo build a wall with a brik type you havent used before, it neds todo download new data files, so it requires an internet connection. To download, go todo http://www.brick.com/, and click on Acme masonry design tool on the right hand side.


quick texturing a large number of objects.

The escenario is the following: you have a large number of woden planks (concrete columns, etc), which you want todo texture quickly. You dont want the texture todo repeat on the planks. A Python script bundled with Blender Will come in very handy: archimap UV projection Unwrapper. First we Will ned one texture. Try todo go as high res as posible. Note that the texture should contain only Wood material, if it is of more than one plank, it shouldnt have gaps between the planks, as that would create unnecessary problems using this script. Here i use a close-up of one woden beam. This Will actually be used for Many planks. How? Notice that the texture has Many fine, detailed lines, these Will be enough for at least ten diferent planks.


Getting the model ready. Model the planks, and make sure they are one Mesh object. If not, select them all, and alt-j todo join them. Press for use the menú todo change todo UV face select mode. Select about ten planks. In another window, open the UV/Image Editor. In the image menú, load the texture. In the UVS menú select archimap UV projection Unwrapper.


The default settings are mostly god. One of the settings that concern us here is the projection angle limit. This specifies the angle above which two neighboring Faces Will be broken up into sepárate pieces on the UV map. If the planks are simple 6 sided rectangular prisms (i, stretched cubes), then the default 66 Degrees is enough todo break up the 90 degre angles between Faces. Lets say however that you have a single bevel on the model. (this is generally god modeling practice.) here the Faces are at 45 degre angles todo each other.


Using the default setting Will produce some weird, unwanted shapes (figure 10, yellow arrows). This is bad for several reasons, for example these Thin Faces Will not be parallel todo the Wood Grain, but some Will run across them. But the real problem is that these shapes Will lead todo a non-ideal placement on the UV texture map. Instead set the angle limit todo less than 45 Degrees, lets say 30. Se the new placement on figure 11, the left hand side.


The new placement is better, the Faces are all parallel todo the Wood Grain, and the UV islands are closely placed. However the top half of the image isnt used. Selecting a bit less planks, in my case 9 instead of 10, Will lead todo a better placement that uses the whole image - Meaning that the Faces are assigned a larger part of the image, y, e.: better quality. You might ned a few tries todo get the best placement.


quick tip: todo select one planque in UV face select mode quickly, hover over it and press l. Shift-l Will add todo the selection.


note: all of this could a los be done by hand, g, the UV map on the left of image 11 could be manually stretched todo cover the whole image. The reason for all this experimentation on the number of planks todo texture is todo automate the process with the above mentioned script. If you have a lot of objects, this type of quik texturing can be done in a few seconds, and Will spare you potentially hours of manual UV map creation.

And here we are. A number of planks textured with random Wood textures in - With some practice - Less than a minute.

By zsolt.
www.blenderart.org.
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