Exercise 2: Modelling the Crepidoma

This will be the second exercise of building a Temple in order to get a full reconstruction at the end and learn our tools in the process. You should have done already Exercise 1: Modelling a Doric Column. Although we don't need the column in this exercise, we will need the knowledge of the last exercise here, which will not be explained again. We will combine the result of this exercise with the column later. This chapter is concerned with the creation of the Crepidoma. You will find a written text below or if you prefer a video to go along directly here. Both ways cover the exact same topics, so choose what suits you the best. To start the project, please download this Cinema4D Package and unzip it into a folder of your choice. It is important to extract the ZIP archive somewhere, rather then to simply open it up and navigate inside the ZIP. If you do not extract the ZIP, you will not find the attached background images.

Cite this video as: Hageneuer, S.: Teaching Archaeoinfomatics! - 3D Reconstruction - Exercise 2 - The Crepidoma. 2020. https://doi.org/10.5446/67631.

Date/Version OS Software Version Length
2020-04-24 🪟 Windows Cinema4D R20.059 Studio 18:08 mins

Creating the Crepidoma: two ways

The basis (also called Crepidoma) is literally the first step into the temple. Once you open the Cinema4D file, you'll see nothing. If you hit F5 to see all the viewports, two of them should have background images visible. We now have to think about how to reconstruct the basis of the temple, so the ground where our columns will stand upon. Of course there are many different ways, but we learn two different ones today: Spline Modelling and Box Modelling. Both ways lead to the same result, but I urge you to try out both ways, so that you can compare the different approaches to the same modelling problem. Later on, you will have to decide on your own which way is the better one to use or in other words which modelling method you prefer.

Spline Modelling

In this kind of modelling we use Splines and Generators in order to reach our goal. The advantage of Spline Modelling is a kind of flexibility with the interpretation of them. So for example, if we create a staircase, it is relatively easy to round the edges or add more subdivision. Spline Modelling is also easy on computer performance. You already are familiar with Spline Modelling, as we already used that technique in our first exercise of creating a Doric Column. There, we used the Loft Nurbs and the Lathe Nurbs. Today, we'll also be using the Loft Nurbs generator.

To start, we create a Spline of the outer shape of the lowest step. We change into our Top View (F2) and select the Pen Tool from our Spline Menu on top (see screenshot). We have to click on the four corners of our plan and then once again on the first point created to close the Spline. Have a closer look at the screenshot, which shows the finished Spline (in red) and the location of the Pen Tool in the tool menu on top. The next step now should be the creation of a surface that is defined by the borders of the Spline. We can do this in many ways, but for our purposes, we need the Loft Nurbs generator, which you'll find in the generator menu on top (click and keep pressed until the sub-menu opens). You also find the tool under the menu Create/Generators/Loft.

In order for the generator to work, we should tell him to use our newly created Spline. To do this, we simply have to make the Spline a child of the Loft Nurbs generator. This means, we have to click & drag the Spline into the Generator, so it becomes the sub-object of it. As you can see, the Spline we created should be filled now with a surface. A minor problem is now, that we can't see the plan anymore. We can fix that by selecting the parent object Loft and in the Attributes Manager select the tab Basic and check the box besides X-Ray. This way, we can see through the object to continue our work. We now need to think of our next step. To do that, we need to understand how the Loft Nurbs generator works. It basically connects Splines. So if you have for example a row of different Splines besides each other, a Loft Nurbs can connect them into a solid 3D Object. The shape of the individual Splines don't have to be the same. The generator will interpolate the points in between.

We therefore need to create now all the “folds” of that staircase, meaning that we have to put a Spline everywhere, where we want the 3D object to change direction or size. The first step would be to create the first step of that staircase. To do that, we simply have to tell the Loft Nurbs, where the outer shape of that stair would end. As we now only have a flat surface, which represents the basis of that stair, we need to put another Spline with the same dimensions a bit higher than the basis. You'll get it as soon as we have done it. Copy the already existing Spline in the Loft Nurbs generator by selecting it and then hitting CTRL+C and CTRL+V. A second Spline should appear on top of your Object Manager. Drag & drop that in the Loft Nurbs, but make sure it is on top of the already existing Spline (see screenshot).

The next step is to elevate that newly created Spline to the correct height. To do so, change into the Front View by hitting F4 and make sure you have selected the new upper Spline in the Loft Nurbs. Use your Move Tool E to move it up as you see it on the projected plan in the background. Make also sure, that you are not in Point/Edge/or Polygon Mode, rather then in Object Mode on the left side. You only have to lift the Spline a little bit for this first step. Do you see the 3D object appearing? You have built your first step, well done! We now need to create the second step. For this, we somehow repeat the steps from before. First, we will build the basis of the second step and then copy that basis to move it up. Sounds easy enough, but how to do it?

To create the basis of the second step, we need again a copy of the uppermost Spline and put it on top in the Loft Nurbs list. So copy & paste the upper Spline (because it already has the correct height) and go into Top View F2 to adjust the dimensions. Use the Scale Tool T for that. At the moment the copied Spline has the same dimensions as the first stair, but in fact we need to scale it smaller according to our plan. If you zoom into one of the corners, you are able to see the scaling better. It should be visible, because we scale proportionally and the structure of the staircase is not proportionally, that we can either make the horizontal or vertical dimensions fit. If you decide for the side dimensions, we still have to compensate for the upper and lower dimensions. We still use the Scale Tool, but we will turn off the axis directions, we do not need. In this case, I turned off X and Y in order to scale only into Z direction. This way, I can scale the third Spline into the right dimensions.

After that we repeat all the steps from before:

  • Copy the uppermost Spline and put it on top inside the Loft Nurbs
  • Adjust the height in the Front View F4
  • Copy the uppermost Spline and put it on top inside the Loft Nurbs
  • Adjust the dimensions for the next step in Top View F2
  • Repeat In the end, you should have 8 Splines when reaching the bottom of the columns and when you change into Perspective View F1 you should see a 3D Object resembling a staircase. In default settings, we still need to adjust one option of the Loft Nurbs generator. When you select it, find the Object Tab in the Attributes Manager and the option Linear Interpolation. Make sure this option is checked.

Box Modelling

This method is called Box Modelling, because we start with a simple shape (normally a Box or Cube) and work our way from there. In the case of our staircase, Box Modelling is actually the easier way of creating, but it is important to know, that you have many possibilities and under different circumstances, Spline Modelling might be the better choice. If you have already created the staircase with Spline Modelling, you can turn the model invisible, so that you have space to work. To do so, select the Loft Nurbs generator in the Objects Manager and hit both small dots, that you see left of the green hook twice, so both points turn red. You should not see your Spline model anymore.

We start of with a Cube, that you can create by hitting the Cube button in the top row of tools or by navigating in the menu Create/Object/Cube. In the Top View F2 we try to fit the dimensions of our Cube as good as possible with the little golden handles. Here, it also helps, if you make the Cube see-through by checking the X-Ray option under the Basic tab in the Attributes Manager. Don't be too exact, as we will convert the Cube now into a Mesh and then move the points around individually. To do so, we hit the C button (Make Editable) and our Primitive Object gets converted into a Mesh. We can now enter Point Mode by clicking the Points button on the left toolbar. Note, that we don't work with a Primitive anymore, which offers us more possibilities in manipulating the geometry.

We now have to adjust the corners of our Cube to the corners of our plan, but we have to be aware, that we deal with a 3D Object. Every point we see here in Top View are actually two points lying above each other. When we move the corners, we need to make sure, that we move both points. To do so, we will use the Rectangle Selection. To do so, we click and hold on the Live Selection tool on the top toolbar until we get a submenu. In it, we'll find the Rectangle Selection. If we now click and drag a rectangle around the two points of one corner, we can be sure, that we select both overlying points of that corner. You can archieve the same result with the Live Selection tool, but we leave it like this for the moment.

We are now able to move the two selected points to the corner of the plan and repeat that step for all four corners, so that in the Top View, our Cube fits the outer shape of the staircase perfectly. If we have a look at our Front View however (F4), we see that the height is not fitting at all. With the same technique, we can move the bottom up and the top down, so we have our first step ready. Make sure, that this time you not selecting individual corners, rather then selecting all the upper points or all the lower points with the Rectangle Selection. Change into the Perspective View F1. As you can see, we created a first step, although it is rather small. The next steps will be more visible. You can already see here the difference between Spline and Box Modelling.

We now need to define the dimensions of the next step, as we have done during Spline Modelling. There we created a new Spline with the new dimensions. This time we will do it a bit differently. In order to create the dimensions of the next step, we kind of need to create a smaller polygon inside the upper polygon of our first step. To do this, we need to change into Polygon Mode and select the upper polygon with our Live Selection Tool. Now, we can utilise the command Inner Extrude by pressing the i key. If you now click somewhere in the Viewport and drag your mouse (without releasing the mouse button), you'll see the newly created polygon. Try to make it a little bit smaller as the original polygon.

To now get the dimensions right, we change into Top View F2 and use the Scale Tool again to scale your still selected polygon into the correct dimensions. You may encounter some problems with the direction of the polygon. If you have a look at the center of the selected polygon, you'll see that the vertical direction is now Y, therefore if you want to scale in vertical direction, make sure you'll leave the Y direction on in the Heading Menu. If this change of directions confuses you, you can also utilise a trick. Instead of using the object axis to scale, you can also use the World Axis to scale. That is what the fourth symbol of the Heading Menu is for (→ X Y Z Coordinate System). If you click the fourth symbol (or press W), it changes from a cube and axis to a world and axis. If you have a look now on the axis of the selected polygon, you'll see that it now corresponds to the world system and if you scale the polygon, you can use the X and Z axis. Be sure to change the coordinate system back to Object Coordinate System (Axis and Cube).

In any case, we now have to extrude the selected polygon up, so that we get the next step. For this, go into the Front View F4 and use the Extrude Tool by hitting the D key. If you now click and drag the mouse, you'll see that the next step arises. Try to already get the height right, so elevate the step up to the corresponding height on the plan. If you miss it, don't worry, but don't use the Extrude Tool again, as this would create additional unnecessary polygons. If you want to correct the height of the step, simply use the Move Tool to move it up or down, as you still have the upper polygon selected. If you have done that, you now simply have to repeat the above steps for each single stair. When you are finished, you're result should look something like this.

To conclude this chapter, I want you to do one more thing. Something very important in 3D modelling is correct naming and organising your structures. As this project is quiet simple at the moment, we don't need to do a lot of sorting. Naming on the other hand, is something you can do right from the start. I would suggest, that you rename you Loft Nurbs into CrepidomaLoft and your Cube object into CrepidomaBox. You can rename objects by double-clicking them in the Objects Manager. Save your progress and keep your file, as we will continue our work on this in later chapters.

This page was last edited on 2024-05-05 20:01

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This page was last edited on 2024-05-05 20:01

Sebastian Hageneuer
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