Reverse Vertex OrderThe Reverse Vertex Order command is a useful one when modelling. It commonly comes into play when you have been linking vertices to form faces (triangles) with the Face tool on the Model tab in the Toolbox. Vertices must be linked in a counter-clockwise direction to form a face (one that faces outward). When linking vertices it is easy to link them the wrong way. This image shows the front (on the left) and the perspective (on the right) views of a square flat surface composed of nine vertices and eight triangles. Please note that the shading type used in the perspective viewport is Flat Shaded, this can be selected by right clicking the viewport and selecting Flat Shaded from the pop-up menu (the default is Smooth Shaded. We use the Flat Shaded view because it gives a better view of the faces that are causing the problem (they are in black). An explanation for the reason behind this can be found in the section: 3D Theory & Practice in the appendix. The triangles in the upper left and lower right quarters were created using the Face tool, selecting vertices in a counter-clockwise direction as shown in red in the image, therefore these faces face towards the viewer, outwards. The triangles in the upper right and lower left quarters were created using the Face tool, selecting vertices in a clockwise direction as shown in blue in the image, therefore these faces face away from the viewer, inwards. This was done on purpose to show what happens when different vertex orders are used but now if we select the four triangles which are facing inward (away from the viewer) then select Face->Reverse Vertex Order the faces will face outward as shown in this image. As you can see, the wireframe front view has not changed. This is because the command does not change the physical construction of the model, it just reverses the order that the triangle is joined to the vertices. In the perspective view all the faces now face outward as we wanted. If we had selected all eight faces then reversed the vertex order the opposite of the model in the first image would have been achieved, i.e. all faces facing inward would face outward and all faces facing outward would face inward. The menu command Face->Face to Front would have served the same purpose as reversing the vertex order on the four black triangles. With Face to Front you can always be sure that your polygons are facing outward rather than using Reverse Vertex Order with which you can't ever be absolutely certain that your polygons are facing the correct way, i.e. outward.
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