In this tutorial we will explain what a transformation is and how these can be performed in Model Lab.

A transformation is a function or operation that that takes a point as input and outputs a new point. When talking about 3D-models the points that are to be transformed are called vertices. Typical transformations are:

• Scale
• Rotate
• Translation

Next you will learn more about these transform operations and how you can use them in Model Lab.

• Download the following model file: chair with transformation issues
• Open Model Lab and import the model.
• Expand the Transform controller.

• Next you will get a brief introduction to the different sub sections in the Transform controller.
• Pivot: The pivot is simply a point in space, also referred to as pivot point. You can think of the pivot point as the local origin of the model. It is basically the same thing as the position of the model with an important difference. If you change the position of the pivot point it does not move the geometry in the model, you only move the local origin. The geometry in the model is only moved when a transformation operation (scale, rotate or translate/position) is executed. You should also note that the pivot point that remains fixed (does not move) during scaling and rotation. You can input your own values to define the pivot point, but usually you are better off using the quick buttons, Lower left and Center.
• Scale: The scale simply defines the dimensions of the model. You may adjust the scale of the loaded model by changing the slider or input field to the right of the slider. The value to the right can be thought of as a magnifier. For instance, by setting it to 2, you will double the size of the model. By setting it to 0.1 you will reduce the size of the model to a tenth of the original size. You can also change the scale by inputting a desired width, depth or height. The values in parenthesis display the original size. Also, if you know you have a lot of models that need to be downsized using the same scale, you can use the remember scale option. It will automatically change the scale of the model during import. All the scaling operations are uniform which means that if you for instance double the width value, the depth and height values will also be doubled.
• Position: Here you can input the position of the model, also known as the translation. You have two quick buttons that can come in handy when you want to position you model quickly, Move to origo and Place on floor. Move to origo will move the model so that the local origin is in origo. If you read the pivot section you will know that the local origin is the same as the pivot point. So in other words, Move to origo will move the model so that the pivot point is in origo. Place on floor will move the model so that its axis aligned bounding box is on the floor.
• Rotation: Can be used to change the rotation of the model. Keep in mind that the position of the pivot point affects the outcome of a rotate operation.
• Hint: Notice that the input fields are marked red, green and blue. This corresponds to X, Y and Z. So as long as you remember RGB you will know if you are changing X, Y or Z.
• Please re-open the model if you already played around with different transformations described above.
• Begin by adjusting the scale. Currently the width is 22m. A chair is more likely to be around 0.5m in width.
• Input 0.5m as the width. Notice how the depth and height are uniformly scaled.

• Now we need to rotate the model -90 degrees around the X-axis.
• Input -90 as the rotation for X. Model Lab will automatically interpret this as 270 degrees which will result in the same rotation as rotating -90 degrees.

• The chair is still floating in the air. Don’t worry, this can be easily fixed.
• Set the pivot point to the lower left corner of the model by clicking Lower left under the Pivot section.
• Under Position click move to origo. This will move the model so that the pivot point is positioned in origo. It is worth repeating the difference between changing the pivot point and changing the position of the model.
  • If you change the pivot point the actual geometry will not move, however the position of the model will be updated since it is defined by the same position as the pivot point.
  • If you change the position both the position of the model, pivot point and the geometry will be updated.
• The final result should look like this:

• That’s it! Now you should know:
  • What a transformation is.
  • What a pivot point is.
  • How scale, position and rotate operations can be performed in Model Lab.

Next: Tutorial 4: Level of detail