This site is maintained as a living document, retaining starting points for ideas followed by their proofs of concept and evolution over time.
The following links share historical references to my descriptions of using miters and spirals in shaping knits.
My earlier posts tended to be brief; the first in the series below dates back to more than a decade ago.
Miters and spirals: visualizing, charting (and more) 1
Miters and spirals: visualizing, charting (and more) 2
Miters and spirals: visualizing, charting (and more) 3
From Revisiting miters, spirals, going square, round, and more
For miter with shaping and resulting eyelets at the center of the triangle: begin with all knit row(s) (red line) at the start.
To shape a full wedge: *green segment is worked, bringing stitches into hold opposite the carriage at the determined rate until all the needles are in hold. Shaping is next reversed with the yellow segment, pushing needles back at the determined rate until all needles are returned to work.
End with all knit row(s) (red line) *. The sides of this miter are all knit rows, an easier place to seam/ graft joins if needed.
Shaping with resulting eyelets at the center of the triangle: the final shape working with starts with COR (Carriage On the Right).
The knitting sequences for when shaping from the left and from the right. 
If the color changer comes into play, then the design repeats, and their starting sides may need to be adjusted accordingly.
Pursuing the six-pointed star/ snowflake challenge, the first test in this series was executed with hand selection, and the knit carriage set for hold.
To get points, not curves, sequential miter shapes are used, and for the easiest counting of segments and seaming/ grafting at the end of each piece, the eyelets are planned to occur at the center of each miter and are retained as design features.
In the photograph:
1: 2/8 wool, random color, casually planned holding sequences
2: using the formula for hexagons planning for 4 stitches being held every six rows, using a 1, 1, 2 sequence 
The repeat, 14X38, as a BW PNG planned for use with the knit carriage set to slip in both directions 
to knit on the 930 as it is drawn, it needs to be reversed 
The first preselection row is made from right to left, picking up the yarn for the star on the left, knitting the first row back to the right, and then repeating selections for pairs of rows until the last segment has been knit, ending with one last row knit across all the stitches.
On punchcard machines the shapes are punched as provided, consider that the punched holes in the card represent what happens on the purl side, and is automatically reversed. One way to correct for that is to insert the card flipped over, thus losing numbering sequences in many cases, or to mark up and punch the card on its back side, then insert it in the usual orientation when ready to knit.
Punching need not be centered, air knit to double check proper needle placement for the first all knit row.
On any machine, end needle selection is canceled.
3: when you don’t have enough light on to notice the yarn you you just pulled from the yarn mast you are about to use is not the same, even in color, as you plan a slightly smaller repeat, the repeat is 12X34
Visualizing some of the differences in shaping between the 2 sizes
4: the same repeat, trying out a softly spun rayon to perhaps render a flatter item, it measures 6 inches across the diagonals. 
A tempting cone of an unknown fiber spun combined with a strand of sparkly led to one last try with the 14 stitch design repeat, the result measures seven inches along its diagonals. The swatch was folded, steamed, and lightly pressed on the knit side along eyelets, measures 7 inches on its diagonal.
The center hole is inevitable in these techniques.
With practice gathering to close it can be improved, here it is performed casually.
How small can one pursue the shape? 10X18
The result diagonals measure 2.75 inches. 
The best intentions for grafting the join were met with tiny stitches and stiff yarn not wanting any part of it, so the closure was with a latch tool again.
If the latch tool bind off is used, the work can be removed and turned over to have it appear on the purl face rather than the knt.
Groups of swatches may be layered, exploring their relationships in different ways.
Increasing the number of rows at the center edge of each segment repeat may create a sharper point.
More seaming ideas including including grafting on both the knit or the purl side in Seaming, joining, picking up stitches on knits 1 .
There are always beads or crochet edgings to ponder adding, then deciding when more is less.
Stiffening knits for sculptural effects can be achieved using any mixtures described as suitable for stiffening crochet doilies. Video and written directions are easy to find online.
The formulas include mixtures using:
sugar, 2 parts sugar to 1 water
white glue, 1 part glue to 1 part water
commercial products such as Mod Podge Stiffy and Aleen’s Stiffen Quick.
A fellow student back in my textile degree days wove yardage for a tryptic that was intended to be displayed on a wall, was draped over life size forms after being dipped in wall paper glue as stiffener, something that worked well, though it was summer and fans were used to speed up drying. Not sure if at the time that was a necessity or out of need for meeting a critique deadline.
If symmetry matters for flat images consider a template drawn on a non permeable surface and patting the item in place.
Felting yields stiffening of a different sort.
As for stiffening felt itself, acrylic medium mixed with water, gelatin sizing used in millinery, PVA glue, and a range of bad for your lungs or melt in the rain concoctions have been mentioned, and then there is the simple, “beat it vigorously” approach, which may not be the best for retaining 3D or sculptural forms.
There are always more rabbit holes to explore.