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Visual Reality: Tutorial: Hexagon: Using the Orient Normals Exercise

Visual Reality: Tutorials: Hexagon: Orient Normals

Exercise: Reversing and Unifying Normals on A Sphere

This exercise walks you through the various ways that you can use the Orient Normals tool, including: reversing normals on individual and on all facets; reversing normals on pre-selected and on non-preselected facets; and unifying facet normals on an object. It also illustrates how to use the Show/Hide Backfaces button to determine if facets on an object are backfacing.

This exercises uses the following tools:

Selection Mode Panel
  Select Faces
  Paint Mode
  Extend Selection
Vertex Modeling Tab
  Create Sphere
Utilities Tab
  Orient Normals
3D Drawing Styles Panel
  Show/Hide Backfaces (backfaces shown, click to hide)
  Show/Hide Backfaces (backfaces hidden, click to show)

Although this exercise includes features of each of these tools, it does not cover all fields and options for them. For additional information and instructions on using a tool, please read the tutorial dedicated to that particular tool.

  1. Open Hexagon. A new file is automatically created.
  2. Press the 2 key to change to the front view.

         OR

         Click View on the Hexagon menu, and then click Front View.
     
  3. On the Vertex Modeling tab, click the Create Sphere button .
  4. Click in the workspace to define the starting point for the sphere.
  5. Drag the mouse to define the diameter of the sphere. For this exercise, use a diameter of about 10.
  6. When the Diameter fields in the Tool Properties window display a value of about 10, click in the workspace again to set this as the sphere's diameter.
  7. Press Enter or click Validate to create the sphere and close the tool.
  8. On the Utilities tab, click the Orient Normals button .
  9. In the Tool Properties panel, click the Reverse Normals button .

Note: Regardless which selection mode you're in, when you click the Reverse Normals button Hexagon automatically switches you to Select Faces mode.

  1. One at a time, click the four facets in the middle of the sphere's front.

Note: You can't use the Paint selection mode to select the facets. If you do, only one facet will be reversed -- not necessarily the first or last one. Instead, you must individually click the facets to reverse if you don't pre-select them before using the Orient Normals tool.

  1. Click Validate or press Enter to accept the changes and close the tool.
 
The sphere after the normals for the four facets have been reversed, with the backfaces hidden.   When you click the Show/Hide Backfaces button to display backfaces, the four facets are visible again, but are a slightly different color from the rest of the sphere.
  1. In the 3D Drawing Styles section of the Control Panel at the bottom of the screen, click the Show/Hide Backfaces button . Since the backfaces of the four center facets are pointing toward the camera, those facets are hidden and appear invisible.
 
The 3D Drawing Styles options are found in the control panel at the bottom of the Hexagon screen. The Show/Hide Backfaces button in this screenshot, the middle icon, indicates that backfaces are being shown.   The icon displayed for Show/Hide Backfaces in this screenshot of the 3D Drawing Styles panel indicates that backfaces are being hidden when Hexagon displays an object.

Note: The Show/Hide Backfaces button has two graphics: Show Backfaces and Hide Backfaces . The graphic displayed indicates which mode you're currently in. It might seem backward to click the show backfaces version to hide backfaces, but you're simply clicking the button to switch to hide backfaces mode.

  1. Click the Show/Hide Backfaces button again so backfaces are displayed. The four backfacing facets are again visible, but are a slightly different shade from the rest of the sphere's facets to indicate that they face a different direction.
  2. In the Selection Mode panel, click the Paint Mode button .
  3. Click and drag the mouse over the four backfacing facets to select them.

Note: You can also press and hold the Shift key while clicking the individual facets to select them.
 
Clicking the Extend Selection button adds two facets on each side of the four initially selected facets.

  1. In the Selection Mode panel, click the Extend Selection button to add the two facets at each side of the selected polygons to the selection.
  2. Click the Orient Normals button .
  3. If necessary, click the Reverse Normals button .
  4. Press the Spacebar. The normals for all of the selected facets are reversed. Those that had been facing toward the inside of the sphere are now facing out, and those that had been facing out are now facing in.
  5. Press Enter or click Validate to accept the changes and close the tool.
  6. Click the Show/Hide Backfaces button to hide the backfaces.
The sphere after reversing normals on the selected facets. The four that had been backfacing are now frontfacing again. The others have been set to backfacing.
  1. The four facets in the center are now visible, but the ones on each side of them aren't.
  2. Click the Orient Normals button .
  3. If necessary, click the Reverse Normals button .
  4. Click the Select All button on the Tool Properties panel. All of the sphere's facets are selected. Arrows indicate the direction that each facet is facing, pointing outward for front-facing facets and inward for back-facing facets.
  5. Press the Spacebar. The normals for all of the facets are reversed.
  6. Press Enter or click Validate to accept the change and close the tool.
  7. The eight facets around the middle that had been invisible before are now visible, and all other facets are now invisible.

Note: It's important to note that the facets aren't actually invisible. They just aren't displayed because Hexagon is set to hide backfaces, and the backfaces of these polygons are pointing toward the camera. If you press 8 to switch to a rear camera view, you'll see that the facets that are invisible from the front are visible from the back and those that you could see from the front are hidden. You're actually looking through the back faces of the facets at the back of the sphere to see the front face -- on the inside of the sphere -- of the backfacing facets on the sphere's front.

  1. Click the Orient Normals button .
  2. Click the Unify Normals button . All the facets are set to face the same direction.
  3. Press Enter or click Validate to accept the change and close the tool.
If you can see the edges of the facets in the back through the facets in the front, the facets are all backfacing.
  1. Click and drag the Camera Rotate Mode button in the 3D Navigation Tools panel to look at the sphere from different angles. Notice that you can see the edges of the facets toward the back of the sphere through the facets at the front. This indicates that the facets are all backfacing.

Note: If the facets don't get set to backfacing when you unify the normals for this exercise, you can complete steps 33 through 38 of this exercise to reverse the normals for all the facets in the sphere and see the effect.

Hint: If you want to create a 360 degree view, you could create a sphere and then reverse the normals on all the facets so they are backfacing like this. The texture would be visible from inside the sphere. Set the camera inside it and you'd have a 360 degree view. You could do the same with a cube to create a simple 360 degree room interior.

  1. Press the 2 key to return to a front view.
  2. Click the Orient Normals button .
  3. If it isn't already selected, click the Unify Normals button .
  4. Press the Spacebar. The normals direction indicator arrow will change to point outward, away from the sphere.
  5. Press Enter or click Validate to accept the change and close the tool.
  6. Click and drag the Camera Rotate Mode button to look at the sphere from different angles again. You should no longer be able to see the edges of the rear facets through the front facets, indicating that the facets are now all frontfacing.

Using the Orient Normals Tool
Reverse Individual Facets that Aren't Pre-Selected
Reverse Individual, Pre-Selected Facets
Reverse All Facets of a Selected Object
Unify Normals for All Facets of a Selected Object
 

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