3D Polygon Reduction Tutorial
Posted: Thu Dec 05, 2002 8:50 am
Actually, I do wish now that I had thought to use some symmetry in this tutorial. Typically, I only use symmetry on meshes for which I feel would be too troublesome to manually edit both sides. Since I was just using basic transformations so far, I didn't think it necessary to use symmetry. The next section, on the other hand, gets a bit more detailed and it would have been nice to use symmetry. Hmm. I think I can work some symmetry into this next section...Why, yes! Part Two: Good Modeling Techniques for Low-polygon Counts (continued)Setion 2-E: Advanced Knifing and Bridging Assuming you unhid all the polygons at the end of section D, now select and hide all polygons except those recessed in the intakes.We're going to select one of these intakes, remove it from the current mesh, and use it in a separate mesh which will later be mirrored and added back into the original mesh. So, follow the next few steps carefully.Select all the polygons for the port side intake (the one on the right from the top view). Choose Split from the Structure - Edit Surface menu. This will create a new object containing a duplicate set of these polygons. The first mesh's original polygons, however, will still be selected in the view. You should delete all of the polygons that compose both intakes on the old mesh because they will be replaced later with the symmetry. Choose Select All from the Edit menu (only the intakes should be visible and selected since you hid everything else) and press delete.The new object will have the same name as the original object but with a ".1" suffix added. Select this new mesh in the Object Manager. Switch the the top 3d view and be sure the Use Polygons tool is enabled. From the Selection menu, choose Deselect All. Switch to the knife tool and drag across the entire mesh, adding polygons like seen here:Now, select and hide these new narrow polygons on the front edge. The reason I added this extra strip was to move the struts inward slightly so they will not be flush against the hull of the ship. You'll see how it all comes together in the next few steps.Though, before knifing in the areas for the struts, you should enable grid snapping so you can be sure the struts will be a precise width apart. To do this, go to the Snap Settings dialog and check the Enable Snapping box. The grid is currently too widely spaced for my needs. So, click the World Grid tab under the Snap Settings, change the Grid Spacing value to 50 m, and press return.With snapping enabled, the cursor will automatically jump to the grid points (and other places if specified) when within a given radius. This helps to make more precise movements with the mouse.Enable the knife tool and drag it over the following lines, using the snap to stay perfectly vertical on the grid:Once you've done that, you can uncheck the Enable Snapping box. Now come the slightly tricky steps. First, hide the polygons on either end like this:Then select the narrow polygons you just made like this:Delete those polygons. You're going to bridge new polygons in their place that will make up the entire struts. Switch on the Use Points tool and enable the Bridge tool. It may help to use wireframe mode in your perspective view now. Bridge the following points in this order:Repeat the same order on the points for the left strut. You're now finished manually adding the struts! That wasn't too hard, was it? Switch to the Use Polygons again and choose Unhide All from the Selection menu. Switch your view mode back to Gouraud of Quick Shading and examine your work. You'll notice that the front edge looks a bit cluttered. There's really no way around this without adding more points to the front edge. It's not so many polygons, really. There are only 6 triangle on the top front edge and 6 on the bottom, but they are packed tightly together.Anyhow, we are now ready to add a symmetry object and then merge the intakes back into the original mesh. First, select that original object in the Objects Manager and unhide all of its polygons. Next, add a symmetry object to the scene and arrange the objects in the hierarchy like this:Select the top object "ship" and chose Current State to Object from the Functions menu. A new set of objects it created and selected. Now select Connect from the Functions menu and a final object is created. You can now safely delete the other two object sets.This mesh is just one step away from completion. It needs to be optimized to join the overlapping points where the symmetry meets the original mesh and to remove the points that were left in the original when you deleted the intake polygons (points always remain after deleting polygons). To do this, select the object and enable the Use Points tool. From the Selection menu, choose Select All. Finally, choose Optimize... from the structure menu. The default settings in the box are fine; so, click OK.Your new, optimized Ocean Patrol Fighter fuselage is now complete! :biggrin:Add some lights with shadows to the scene are render a sample shot.Now, treat yourself to a nice, refreshing beverage. If you were able to follow my instructions this far, then you've well earned it. Just for kicks, I summed the object information totals for these parts in your original file and then for this final mesh. Curious about the difference? The fuselage of the old model had 313 polygons made from 286 points, using 18 kilobytes of memory. The new model has 98 polygons made from 86 points, using 5 kilobytes of memory. In part three, I'll use a boolean to remove a complex part of an object and then clean up and try to optimize any mess it makes on the surface.