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Cyberware designs, manufactures, and sells standard and custom 3D scanning systems and software. | |||||
Most of the following remains valid, however, if you are using Echo software of recent vintage (Release 3.0 and beyond), the caveats contained herein regarding command usage for the border command can be disregarded.
The following discussion does not include any references to the use of the Surface Tools feature of Echo or the gradlim command in attempts to improve the appearance of the transition zone between the periphery of a relief image surface with a background surface treatment. Both tools have been tried more recently, in combination with various other tools and with varying degrees of success. A discussion of their use is in progress.
See also Part II and Part III.
Most instances of relief preparation involve conversion of a selected view of a cylindrical image for the head and shoulders of a human subject. The relief conversion transforms the graphically displayed view into a Cyberware image of the cartesian type. A variety of editing techniques can be applied to the original image so as to achieve certain esthetic or special effect objectives. On the other hand, satisfactory relief conversions can be achieved with little more editing effort than that required to fill interior voids, perhaps clip the latitude range and the radius range in the shoulder region and to apply a toupee treatment.
This discussion assumes that the process will begin with a raw relief image transformed from the user's choice of a displayed view of a cylindrical image. This resulting raw relief image, however, will possess a background consisting entirely of void points and consequently no bordering feature. Creation of bordered backgrounds into which a suitably proportioned image can be embedded to achieve a composite medallion or cameo treatment is the primary motivation and focus for the material that follows.
The border command available to you from the Echo prompt is intended to provide the basic elements necessary for creating various background and border designs. Used in conjunction of with other Echo commands a surprisingly rich assortment of bas relief, medallion, and cameo designs can be created. Even though the sequence of steps leading to a pleasing presentation might appear to be amenable to an Echo source script that would automate the sequence in a standard way, far better results are achieved interactively because of the variability in relative depths of features in relief images obtained from different subjects and/or various views of a given subject.
The creation of backgrounds and borders is simplified somewhat if the step involving depth proportioning of the subject relief image is accomplished first. This requires that you decide on the relative depth compression of various image feature that you would like to achieve. Furthermore you need to decide if you would like that compression to be achieved by linear or non-linear proportioning techniques. The undocumented and misnamed rlogprop command is available from the Echo prompt allowing non-linear as well as linear proportioning strategies to be applied.
The rlogprop command may be invoked without option flags specified, in which case only one numerical argument will be expected. That argument is a constant percentage factor by which all depth value in the image will be multiplied. Alternatively, the standard rprop command could be used for this type of simple depth proportioning. Otherwise the rlogprop command is invoked as follows:
| echo > rlog -option prop_max prop_min depth_hi depth_lo |
The option flag may be set to -r, in which case all depths greater than depth_hi will be proportioned by the percentage factor prop_max, all depths less than depth_lo will be proportioned by the factor prop_min and all depths lying between depth_hi and depth_lo will be proportioned by a factor that varies linearly from prop_max at depth_hi to prop_min at depth_lo. The -t option regime is very similar, however, it differs in that the percentage factor by which depths are proportioned in the transition range varies sinusoidally rather than linear from prop_max to prop_min.
The advantage of using the non-linear proportioning available with rlogprop lies in allowing features nearest the viewer to retain their relative depths to a greater extent than more distant features. The fact that features lying further into the view become most strongly compressed enables the peripheral features to blend more gracefully with a synthesized background surface. This is particularly advantageous in the case of reliefs generated from face-on views of human subject. In this case the features lying between say the corner of the eye and the front of the ear tend to slope steeply away from the viewer yet they occupy a very significant fraction of the overall depth of the raw relief image. The rlogprop command allows the proportioning process to yield progressively greater compression of feature depths in this range.
As an example for the usage of rlogprop, assume that a face-on view has been converted to a relief image and that the resulting image has been metered with the following results:
| Nose Elevation: | 16000 microns |
| Eye Elevation: | -26000 microns |
| Ear Elevation: | -122000 microns |
Furthermore the radius range is found to be from -210000 to 16000 microns and the desired depth of the prominent facial features is about 25000 microns. The Echo software command
| echo > rlog -r 30 10 -20000 -140000 |
...or...
| echo > rlog -t 30 10 -20000 -140000 |
would be reasonably appropriate. A 30 percent proportioning factor is applied to all features at or above -20000 microns, a 10 percent proportion factor is applied to features below -140000 microns and the proportioning factor varies increasingly from 30 percent at -20000 microns to 10 percent at -140000 microns.
Note that the average proportioning factor for the mid range is 20 percent so it is reasonable to expect the resulting proportioned mid range of depths to be about 20 percent of 120000 microns or 24000 microns. Furthermore it should be noted that the relative depth values for the entire raw relief image could have been shifted with the rincr command so that the features of interest would have positive values if more convenient. In any event, the subsequent task of background and border creation will necessarily require some adjustments of the image elevation relative to the background and border so the proportioning step should be accomplished in whatever way enables you to concentrate upon and achieve the relative feature relief you desire.
Now assume you have saved the proportioned relief and that metering on the image gave the following results:
| Nose Elevation: | 5000 microns |
| Ear Elevation: | -20000 microns |
Further assume that the overall radius range is now from -40000 microns to 5000 microns and that you would like the features at about -30000 microns to blend into the background. This means that, for a flat background, the lower lip of a border would need to be at -30000 microns or, for a dished background, the elevation of the lower lip of that border will be sufficiently higher so as to accommodate the extent of background curvature. The elevation and width of the border's rim will be a judgment call based on your design objectives and/or stylistic preferences.
If only interested in a flat background and if you want a circular border 20 mm high and 5 mm wide, the following procedure should suffice. The image should be voided completely with the intset command. Now create your flat background using the border command as follows:
| echo > border -30000 -30000 250000 |
This sets the lower inner lip of the border at -30000 microns, the elevation of the rim proper also at -30000 and the width of the rim to a value greater than half the image width thus generating a circular disc at a constant elevation of -30000 microns. Next enter the command
| echo > border -30000 -10000 5000 |
which will then generate a circular rim occupying a 5 mm wide band of the disc's periphery. The lower inner lip of the rim will coincide with the elevation of the disc and the rim will be 20 mm high, i.e., its top will be at the elevation -10000, i.e., 20 mm above the disc. You may choose to save the composite border and background image but it is not really necessary since it is fairly easy to recreate.
On the other hand, if you want a rectangular border, you need to specify the -r option when using the border command. This will result in the creation of a rectangular rather than circular border. The procedure for specifying the various arguments to the border command will be exactly analogous to that used above in creating the circular bordered flat background. An alternate, perhaps even simpler way of generating rectangular borders might be to employ the standard Echo commands latitude/longitude range, intset, extset, etc.
Note: A rather irritating bug exists in the border command for Release 2.0 that causes the numerical arguments to be interpreted wrongly whenever the -c and -r option flags are specified. Fortunately, the circular border option is the default and in the absence of the -c flag, the command works as intended and assigns the values for the arguments correctly.
If you want to use the border command to create rectangular bordered backgrounds you will need to specify the -r option. This means that you are then forced to understand the nature of the bug and its work around. The -c and -r option flags correctly set the border type but the lower inner rim elevation is never set therefore the top of the rim is set to the value intended for the lower lip. Subsequently the rim width gets set to the value intended for the rim's top elevation. Finally, the aspect ratio, if specified, will be interpreted at the rim width. Needless to say, you might find the results somewhat less than optimal.
Rectangular borders can, nonetheless, still be created using the border command if you remember that the -r flag must be specified. Having done so, you will need to remember that the rim's lower inner lip elevation will now take on some unspecified (garbage) value, the elevation of the rim's top will be assigned the value specified by the first of the three numerical arguments, the rim's width will be assigned the value of the second such argument and the third argument should not be included unless you wish to specify an aspect ratio. Since the garbage elevation of the inner lip will most likely lie outside of the depths intended for the border, use the radius range command to force these inner lip depths to the level you want.
Alternatively, rectangular borders might be more easily created using the standard Echo commands latitude/longitude range, intset, extset, etc.
At this point you should begin to compose the composite image by using the paste command, first with the -n option followed by its use with the -v option. The command
| echo > paste -n filename |
will generate within the currently resident image a void region, which is the negative or silhouette of the relief image saved as filename. This then allows the command
| echo >l paste -v filename |
to replace filename's silhouette with filename's actual image. Try it, you'll probably like it. Now study your result particularly with regard to the match between the irregular relief image boundary features and the background. If the background appears to be too high or low, meter enough points to estimate the average mismatch and then repeat the two foregoing paste commands but with one additional command between "pastes". After the first paste, which is like pulling the relief image out of a puzzle, raise or lower the resulting resident image by the amount estimated above using the rincr command. Now do the second paste operation, which replaces the missing piece of the puzzle but with a much better match between image and background.
The combined image should now be a satisfactory albeit "stiff" version of coin or cameo, which can be scaled, proportioned, smoothed, etc. A somewhat more stylish treatment can be achieved by trying one or more of the techniques that have been employed for improving the aesthetics of the transition region between the relief image and the background.
The simplest of these techniques is to subject the composite relief to an aggressive smoothing operation such as would result from the command
| echo > rep 3 smooth -p 2 2 |
This will soften the rim considerably but more importantly it will greatly improve the areas of the product at the transition from background to the actual image.
An even more effective treatment of this transition zone would result from using the Select Points Void Selected provisions of the Surface Tools feature. Removal of a band of points around the periphery of the image followed by one or more selective uses of the fill command will result in a wider transition zone between image and background. The subsequent smoothing operation is then even more effective in reducing the severity of the more obvious mismatches in elevation between the image periphery and the background.
In either event, once this latter smoothing operation is accomplished, the saved, unsmoothed image portion will need to be re-embedded using the two-step procedure involving the paste command.
Creation of dished backgrounds is a bit more involved but if you have experimented with the rsinprop command you will probably find it relatively easy. The trick is to determine the degree of concavity that you think will be appropriate for the image/background combination you find pleasing. The rsinprop command with the -b option flag allows you to specify a peak relative proportioning factor to be applied to the data within the range window in such a way that the actual factor for each point varies in both the vertical and the horizontal directions with a selected interval along a sinusoidal waveform.
In our case this proportioning is most easily effected by first creating a circular disc as was done at the outset of the background generation described above only this time set the elevation at 10000 microns. This will make it simpler to experiment with various degrees of background curvature. As we have demonstrated, it is fairly easy to shift the resulting image up and down in depth as necessary. Given a circular disc at 10000 microns, the command
| echo > rsinprop -b 10 512 0 |
will result in a concave disc whose peripheral data points will all remain equal to their initial values. The disc surface will be increasingly depressed as points midway between rim and center are approached after which they will continue to be depressed but at a decreasing rate of depression until reaching the maximum depression at the disc's center. In this case the elevation at the disc's center will be 1000 microns, which is 10 percent of the original disc elevation and the elevation at the disc's mean radius will be 7071 microns, i.e., 0.7071 times 10000 microns.
Please note that the -b option flag is essential for this application and please recognize that you will always need to begin with a disc whose constant data values are non-zero otherwise rsinprop won't be of much help. You need to keep in mind that if you create your disc at an elevation less than zero, for example -10000 microns, you will need to use a proportioning argument that is greater than 100 in order for the disc to cup toward the viewer. If on the other hand your intent is to force the bottom of the cup to be at -10000 microns you will need to specify that the nodal latitude is 255 rather than 0 so that the proportioning proceeds progressively outward toward less negative values and reaches a value of -1000, i.e., 10 percent of -10000, at the periphery.
You must keep in mind that if you want to create elliptically bordered reliefs, you will first need to create a corresponding elliptical background disc. For example, the command
| echo > border 10000 10000 250000 125 |
will generate an elliptical disc at 10000 microns elevation whose vertical extent will exceed its horizontal extent by 25 percent. If a flat background will suffice for your purposes, the command
| echo > border 10000 rim_elevation rim_width 125 |
will produce the desired elliptical rim for your flat elliptical background.
The somewhat more involved case of generating a dished elliptical background requires that you locate the first and last non-void longitude for the starting (flat) elliptical disc you have created. Set the longitude range accordingly, either explicitly or using lgrange -a, and then invoke the desired rsinprop command, for example,
| echo > rsi -b 25 512 0 |
Setting the longitude range as described above will ensure that the blended proportioning regime will preserve the original elevation values at the actual elliptical periphery of the disc's surface. Now the command
| echo> border 10000 height width 125 |
will result in the desired dished and elliptically-bordered template into which your relief may be embedded in a manner analogous to that described above. You will undoubtedly need to ensure that the basic shape of the image you are attempting to frame within the template is consistent with the degree to which that template is elongated. If you do not, the embedding process can easily result in portions of the subject image overlapping the rim.
Finally, in order to actually machine the types of relief images we have been ginning up here the void regions exterior to the desired composite image must somehow be set to reasonable values. It will probably prove to be useful to leave these regions void until such time as a particular machining run is planned so that a copy of the image can be scaled and proportioned as desired. At that time an appropriate elevation can be determined for this exterior region and set accordingly using the voidset command. A final note of caution here is that you should always fill -i the composite bordered relief so that a stray void(s), particularly if interior to the embedded image, won't inadvertently get set to the voidset argument value rather than one consistent with the neighbors.
