A complete reference for the Deck Builder formula engine — every variable, every function, every operator, with worked mining examples grouped by use case.
Other engines: Print templates and blast groups use different
fx:variables and functions. See the Formula Engine hub before copying formulas between Deck Builder, XLSX reports, and Assign Group.
A blast rule applied to one hole becomes mechanical when applied to a pattern of 300 holes. Hole lengths vary, stand-off distances vary, ground conditions vary. Kirra’s formula engine lets a single rule template re-evaluate itself per hole — so a stemming depth of “back off enough room for 25 kg of ANFO” or “stay under 4 mm/s at the monitor” becomes one formula that produces the right number for every hole automatically.
Formulas can be typed into any of these fields in the Deck Builder dialog:
fx: prefixEvery formula starts with one of two prefixes:
fx: — the production form. Excel and Google Sheets won’t try to evaluate it as a spreadsheet formula on CSV round-trip. Always use fx: for anything that may be exported.= — legacy / internal form. Still works but Excel will mangle it on CSV import. Avoid for new work.Kirra has two formula evaluators that share the same syntax but differ in return type:
| Evaluator | Returns | Used for |
|---|---|---|
evaluateFormula |
number | Top/Base/Length/Mass/Primer Depth fields |
evaluateFormulaBoolean |
boolean | Swap predicates, conditional rule gates |
Boolean evaluator accepts string equality (e.g. holeType == "Production"); numeric evaluator coerces every variable to a number. Same operators, same indexed variables, same ternary syntax in both.
| Group | Variable | Type | Notes |
|---|---|---|---|
| Hole geometry | holeLength |
m | calculated length, collar→toe |
holeDiameter |
mm | as drilled | |
holeX |
m | collar X (UTM easting) | |
holeY |
m | collar Y (UTM northing) | |
| Charge totals | chargeLength |
m | sum of all explosive (COUPLED/DECOUPLED) deck lengths |
chargeTop |
m | top of shallowest charge deck | |
chargeBase |
m | base of deepest charge deck | |
firstChargeTop |
m | top of shallowest charge deck | |
| Inert totals | stemLength |
m | sum of stemming (INERT/Stemming) deck lengths |
inertLength |
m | sum of all INERT deck lengths | |
airLength |
m | sum of INERT/Air deck lengths | |
waterLength |
m | sum of INERT/Water deck lengths | |
| Indexed | deckBase[N] |
m | base depth of deck N (1-based, 1 = deepest) |
deckTop[N] |
m | top depth of deck N | |
deckLength[N] |
m | length of deck N | |
deckDensity[N] |
g/cc | effective density of deck N’s product (v1.0.272+) — adapts to product swaps | |
chargeBase[N] |
m | base depth of charge-only deck N | |
chargeTop[N] |
m | top depth of charge-only deck N | |
chargeLength[N] |
m | length of charge-only deck N | |
chargeDensity[N] |
g/cc | effective density of charge-only deck N (v1.0.272+) |
Undefined indexed variables resolve to 0 — use > 0 as the “does this deck exist?” test.
| Function | Signature | Returns | Notes |
|---|---|---|---|
massLength |
(kg, density) or (kg, "Product") |
m | Length needed to hold a given mass at the hole’s current diameter |
sdobStem |
(targetSDoB, density) or (targetSDoB, "Product") |
m | Stem length for a target Chiappetta Scaled Depth of Burial |
sdobKg |
(targetSDoB, density) or (targetSDoB, "Product") |
kg | Inverse of sdobStem — deck mass that achieves the target SDoB at the current hole length and diameter |
ppvKG |
(monitorX, monitorY, targetPPV, K, b) |
kg | Max instantaneous charge at this hole that keeps PPV under target at the monitor — uses site law PPV = K · (D/√Q)^(−b) |
Math.min |
(a, b, ...) |
number | Standard JS Math |
Math.max |
(a, b, ...) |
number | |
Math.abs |
(x) |
number | |
Math.round |
(x) |
number | |
Math.ceil |
(x) |
number | |
Math.floor |
(x) |
number | |
Math.sqrt |
(x) |
number | |
Math.PI |
(constant) | number | π |
All of JavaScript’s Math namespace is available. Common ones are listed above; Math.sin, Math.log, etc. work too.
| Group | Operators | Notes |
|---|---|---|
| Arithmetic | + - * / ( ) |
Standard precedence |
| Comparison | < > <= >= == != |
== does loose equality; use == not === for strings |
| Logical | && \|\| ! |
AND, OR, NOT |
| Ternary | condition ? then : else |
Chains right-to-left — add parens beyond two levels |
Worked examples grouped by use case. Every example follows the format:
Deck[N] Field =
fx:formulaDescription: what the formula does and when to reach for it.
Deck[1] Type = INERT (Stemming) Deck[1] Top =
0Deck[1] Base =fx:1.5
Description: Hard-coded 1.5 m stem from collar. Useful as a default deck before any rule runs. The fx: prefix isn’t strictly required for a constant, but using it consistently keeps the field’s input mode unambiguous.
Deck[N] Base =
fx:holeLength
Description: Whatever deck you place this on, its base = the hole’s measured/calculated length. Use on the bottom-most deck to ensure the charge reaches the toe regardless of as-drilled length variation.
Deck[1] Top =
0
Description: Top of the top deck is always the collar. A literal 0 is fine — no formula needed.
Deck[1] Type = INERT (Stemming) Deck[1] Top =
0Deck[1] Base =fx:holeLength*0.3
Description: Stem occupies 30 % of hole length. Bottom 70 % is available for charge. Auto-scales with hole length so deeper holes get longer stems proportionally.
Deck[1] Base =
fx:Math.max(Math.min(holeLength*0.3,4.0),1.5)
Description: Stem is 30 % of hole, but never less than 1.5 m and never more than 4.0 m. Math.min caps the upper bound; Math.max enforces the lower. Production-safe form when hole-length variation is wide.
Deck[1] Type = INERT (Stemming) Deck[1] Top =
0Deck[1] Base =fx:sdobStem(1.5,"ANFO")
Description: Stem length sized so the Chiappetta Scaled Depth of Burial equals 1.5 for an ANFO charge filling the remainder. Higher SDoB (≈1.5–2.0) = more confined, finer fragmentation, lower airblast. Lower SDoB (≈1.0–1.2) = more cratering, higher airblast. The function reads ANFO’s density from the loaded products catalog.
Deck[1] Base =
fx:Math.ceil(sdobStem(1.5,1.15)*10)/10
Description: Same as above but rounded up to the nearest 0.1 m. Use when stemming is loaded by a truck that can only deliver in 100 mm increments — rounding down would under-stem.
Deck[1] Type = INERT (Stemming) Deck[1] Top =
0Deck[1] Base =fx:Math.ceil((holeLength>holeDiameter*35/1000?holeDiameter*25/1000:sdobStem(1.5,0.82))*10)/10
Description: Combines two industry rules of thumb in one formula:
Math.ceil(... * 10) / 10) so the stemming truck’s 100 mm increment always meets or exceeds the design — never under-stems.The holeDiameter * 35 / 1000 converts mm to metres in-line, so the threshold scales with diameter automatically. Same for holeDiameter * 25 / 1000. This is a real production stem rule used at several Pilbara iron-ore operations — one formula replaces three pages of look-up tables.
Deck[2] Type = COUPLED (ANFO) Deck[2] Length =
fx:massLength(25,0.82)Deck[2] Base =fx:holeLength
Description: A 25 kg ANFO deck anchored to the toe. massLength converts kg to metres using the hole’s current diameter and the supplied density. At 115 mm hole, 25 kg ≈ 2.93 m.
Deck[2] Length =
fx:massLength(25,"ANFO")
Description: Identical to the above but density is looked up from the product catalog. If site changes ANFO density spec from 0.82 → 0.85, the formula adapts automatically. Always prefer the product-name form unless you specifically need to lock the density.
Deck[2] Length =
fx:massLength(holeLength*holeDiameter*holeDiameter*0.0008,"ANFO")
Description: Reverse-calculates deck length for a target powder factor. The holeLength * holeDiameter² * 0.0008 term approximates a 0.8 kg/m³ powder factor; substitute your target. Pair with a stem deck above and let the charge fit the remaining hole.
ppvKG)The ppvKG function returns the maximum charge mass (kg) at this hole that keeps PPV at the monitor below the target, using the site law PPV = K · (D/√Q)^(−b).
Below are seven progressive variants of the same compliance goal — same monitor (36153.16, 156036.286), same target 4 mm/s, same site constants K=1140, b=1.6. Increasing complexity from basic to production-grade.
Deck[1] Type = INERT (Stemming) Deck[1] Top =
0Deck[1] Base =fx:holeLength-(massLength(ppvKG(36153.16,156036.286,4.0,1140,1.6),0.82))Deck[2] Type = COUPLED (ANFO) Deck[2] Top =fx:deckBase[1]Deck[2] Base =fx:holeLength
Description: At the monitor location calculate the stemming depth of the product to get 4 mm/s, link the top of the charge column to the bottom of the stemming deck, and the bottom of the charge to the holeLength. Canonical two-deck PPV-bounded design — every hole sizes its charge based on its own distance from the monitor.
Deck[1] Base =
fx:holeLength-(massLength(ppvMKG("MON-01",4.0),0.82))
Description: Same as #1 but the monitor coordinates and (K, b) are stored on a named monitor entity "MON-01" in the project. ppvMKG(monitorName, targetPPV) is a Phase 2 function (not yet shipped). Until then, use #1’s literal-coordinate form.
Deck[1] Base =
fx:Math.max(holeLength-(massLength(ppvKG(36153.16,156036.286,4.0,1140,1.6),0.82)),2.0)
Description: Same PPV math as #1, but the stem is never shorter than 2.0 m even if the PPV calculation allows a longer charge. Math.max wins when the PPV-limited stem would be below 2.0 m — safer for stem retention at the cost of a marginally more conservative charge.
Deck[1] Base =
fx:Math.min(Math.max(holeLength-(massLength(ppvKG(36153.16,156036.286,4.0,1140,1.6),0.82)),2.0),holeLength-1.0)
Description: Combines #3’s minimum-stem (2.0 m) with a maximum-stem cap of holeLength − 1.0 so the charge column is always at least 1.0 m long. Guards against the edge case where a very deep hole + tight PPV target leaves less than 1 m of explosive — a charge too short to detonate reliably.
Deck[1] Base =
fx:holeLength-(massLength(ppvKG(36153.16,156036.286,4.0,1140,1.6),holeLength>8?1.15:0.82))
Description: Ternary lives inside the density argument of massLength. Deep holes (>8 m) use emulsion density 1.15; shallow holes use ANFO at 0.82. Pair with a swap rule on Deck 2 to ensure the product matches the density used here.
Deck[1] Base =
fx:deckBase[2]>0?deckBase[2]-0.3:holeLength-(massLength(ppvKG(36153.16,156036.286,4.0,1140,1.6),0.82))
Description: “If a second charge deck exists, sit the stem 0.3 m above it. Otherwise, size the stem so the PPV-limited charge fits between the stem base and the toe.” Pattern: if something exists and you want THAT number → use it; else use the formula number. Uses > 0 as the “does it exist?” test because undefined indexed variables resolve to 0.
Deck[1] Base =
fx:deckBase[2]>0 ? Math.max(deckBase[2]-0.3,2.0) : (holeLength>8 ? Math.min(holeLength-(massLength(ppvKG(36153.16,156036.286,4.0,1140,1.6),1.15)),holeLength-1.0) : Math.max(holeLength-(massLength(ppvKG(36153.16,156036.286,4.0,1140,1.6),0.82)),1.5))
Description: Three-way branch:
Production-grade form — every edge case from #3–#6 collapsed into one formula. Once verified against site data it becomes a rule template applied across an entire pattern.
Deck[1] Type = INERT (Stemming), Top =
0, Base =fx:holeLength*0.3Deck[2] Type = COUPLED (ANFO), Top =fx:deckBase[1], Base =fx:deckBase[1]+2.0Deck[3] Type = INERT (Air), Top =fx:deckBase[2], Base =fx:deckBase[2]+1.5Deck[4] Type = COUPLED (ANFO), Top =fx:deckBase[3], Base =fx:holeLength
Description: Stem (30 %) + upper charge (2.0 m fixed) + air gap (1.5 m) + lower charge (fills remainder to toe). Each deck’s top references the previous deck’s base — moving the stem ripples the whole chain. Used to limit peak particle velocity at depth while still loading the bottom of the hole.
Deck[1] Type = INERT (Stemming), Top =
0, Base =fx:holeLength-chargeLength-1.0Deck[2] Type = COUPLED (Emulsion), Top =fx:deckBase[1], Base =fx:holeLength-1.0Deck[3] Type = INERT (Water), Top =fx:deckBase[2], Base =fx:holeLength
Description: Water deck at the toe to dampen toe burden in wet holes. Note chargeLength in the stem formula self-references the sum of all charge decks — Kirra resolves this through the dependency graph as the layout is computed.
Primer[1] Depth =
fx:chargeBase[1]-0.3
Description: Standard primer position — 0.3 m up from the base of the deepest charge deck. Booster sits inside the explosive column, not at the actual toe (avoid contact with toe water / cuttings).
Primer[1] Depth =
fx:chargeBase[1]-0.3Primer[2] Depth =fx:chargeBase[2]-0.3
Description: One primer per charge deck. Primer[1] = bottom charge, Primer[2] = upper charge. Each automatically tracks its respective deck as the layout changes.
Primer[1] Depth =
fx:chargeBase[1]-0.3Primer[2] Depth =fx:chargeBase[2]>0?chargeBase[2]-0.3:0
Description: Primer[2] only places if a second charge deck exists. Otherwise depth = 0, which the rule engine treats as “skip this primer”. Use when a rule template should support both single-deck and decked-charge holes.
Deck[1] Base =
fx:holeLength<5?holeLength*0.4:2.0
Description: Short holes (<5 m) get a 40 % stem; longer holes get a fixed 2.0 m stem. The breakpoint formalises a rule-of-thumb that crews used to apply by eye.
Deck[2] Length =
fx:massLength(25,waterLength>0?1.25:0.82)
Description: If the hole has any water deck above this charge (waterLength > 0), use emulsion density (1.25); otherwise ANFO (0.82). Combines the rule “wet holes need emulsion” with the mass-to-length conversion in one expression.
Deck[2] Top =
fx:Math.min(holeLength-massLength(ppvKG(36153.16,156036.286,4,1140,1.6),0.82),holeLength*0.5)
Description: Charge top sits at whichever is shallower — the PPV-limited length, or 50 % of hole length. Useful when a regulatory PPV cap is sometimes more permissive than the production powder-factor target; this formula always picks the more restrictive limit.
These use evaluateFormulaBoolean — they return true/false and gate swap actions in rule templates.
Deck[2] Swap Condition =
holeType=="Wet"||waterLength>0
Description: If the hole is tagged Wet OR has any measured water column, swap the deck product (configured in the rule template). String equality uses == (not ===). Compatible with both swap template rules and applyChargeRule conditional branches.
Deck[2] Swap Condition =
holeLength>10&&holeType=="Production"
Description: Swap only fires when both conditions hold — deep AND production-class. Use && (AND), || (OR), ! (NOT) freely in predicates.
Deck[1] Type = INERT (Stemming) Deck[1] Top =
0Deck[1] Base =fx:Math.max(sdobStem(1.5,"ANFO"),holeLength-(massLength(ppvKG(36153.16,156036.286,4,1140,1.6),"ANFO")))Deck[2] Type = COUPLED (ANFO) Deck[2] Top =fx:deckBase[1]Deck[2] Base =fx:holeLengthPrimer[1] Depth =fx:chargeBase[1]-0.3
Description: Stem is the larger of two competing requirements:
Whichever is more restrictive wins. The charge fills the remainder to the toe; primer is auto-placed 0.3 m above the toe in the explosive column. One rule, every hole, full compliance.
Deck[1] Type = INERT (Stemming) Deck[1] Top =
0Deck[1] Base =fx:sdobStem(1.4,"ANFO") < holeLength-(massLength(ppvKG(36153.16,156036.286,4,1140,1.6),"ANFO")) ? holeLength-(massLength(ppvKG(36153.16,156036.286,4,1140,1.6),"ANFO")) : sdobStem(1.4,"ANFO")Deck[2] Type = COUPLED (ANFO) Deck[2] Top =
fx:deckBase[1]Deck[2] Base =fx:holeLength
Description: “If the SDoB-1.4 stem is shorter than what PPV requires, the design isn’t PPV-compliant — use the PPV-bounded stem instead. Otherwise the SDoB design is already conservative enough — use it.”
This is the ternary form of the Math.max(...) design above. Mathematically equivalent, but reads as a literal decision:
holeLength − massLength(...)).Threshold 1.4 is the common minimum acceptable confinement for production benches — drop to 1.2 for casting designs where some cratering is desired; raise to 1.6 for noise-sensitive sites.
A combined SDoB+PPV formula has two valid homes. Choose based on what you want to control directly:
| Field | What you control | When to use it | Example |
|---|---|---|---|
| Stem Base (Deck[1]) | Stem length directly | When site standards are written in terms of stem (mm or m) — most production rules | The SDoB-first example above |
| Mass (kg) (Deck[2]) | Charge mass directly | When site standards are written in terms of MIC (Maximum Instantaneous Charge in kg) — most regulatory PPV docs | See below |
Stem Base form (current workaround, works today):
Deck[1] Base =
fx:Math.max(sdobStem(1.4,"ANFO"), holeLength-(massLength(ppvKG(...),"ANFO")))Deck[2] Top =fx:deckBase[1]Deck[2] Base =fx:holeLength
Both sdobStem(...) and holeLength - massLength(...) return stem lengths in metres — they can be compared and max-ed directly. No conversion needed, which is why this is the canonical form.
Mass field form (cleaner after Mass-formula support ships):
Deck[1] Type = INERT (Stemming), Top =
0, Base = (any scaling — e.g. VR Variable) Deck[2] Type = COUPLED (ANFO) Deck[2] Top =fx:deckBase[1]Deck[2] Base =fx:holeLengthDeck[2] Mass =fx:Math.min(ppvKG(...), sdobKg(1.4,"ANFO"))
Where sdobKg(targetSDoB, product) would be a Phase 2 helper that returns the SDoB-compliant kg directly. Until that helper exists, the Mass field can’t naturally express SDoB constraints — keep SDoB logic in the Stem Base, and put fx:ppvKG(...) alone in Mass if you want PPV-only mass control.
Rule of thumb:
Math.max(...).holeLength - massLength(ppvKG(...), "Product").Math.min(...).The Pattern 9 examples above all sit in Stem Base because SDoB is fundamentally a stem-length rule. The Mass-field equivalents exist but require an inverse function (sdobKg) that’s not yet in the engine.
1. holeLength(...) is not a function call.
❌ Wrong: fx:holeLength(massLength(ppvKG(36153.16,156036.286,4.0,1140,1.6),0.82))
This treats holeLength as a function and throws TypeError: holeLength is not a function.
✅ Correct: fx:holeLength-massLength(ppvKG(36153.16,156036.286,4.0,1140,1.6),0.82)
2. Case-sensitivity. holength ≠ holeLength. Typos throw ReferenceError and the field stays blank.
3. Indexed variables are 1-based, deepest first. deckBase[1] is the deepest deck in the hole, deckBase[2] the next one up, etc. This matches the section-view ordering and is the opposite of insertion order in some rule engines.
4. Undefined indexed variables resolve to 0. There is no isDefined() — use > 0 as the existence test: deckBase[2] > 0 ? ... : ....
5. ppvKG’s first two args are the MONITOR, not the hole. The function is bound to the hole’s collar internally. Pass monitor UTM coordinates as (x, y). If you want hole-to-hole modelling, pass another hole’s coordinates.
6. Use product names ("ANFO") over literal densities (0.82). Density spec changes at site happen — product-name lookups adapt; literal numbers don’t.
7. Ternaries chain right-to-left. a ? b : c ? d : e parses as a ? b : (c ? d : e). Add explicit parens for three-way branches — see PPV #7.
8. The fx: prefix is CSV-safe; the = prefix is not. Excel will treat =… as a formula on CSV import and may evaluate it incorrectly (or worse, as a security exploit vector). Always use fx: for anything that leaves Kirra.
9. chargeBase[N] only counts COUPLED/DECOUPLED decks. deckBase[N] counts everything including inert/stemming/air/water. Use the right one for what you mean.
10. Outer parens are optional but harmless. fx:holeLength-massLength(...) and fx:holeLength-(massLength(...)) evaluate identically. Keep them if they help readability.
When Custom CSV charging export/import is enabled, every formula string survives a round trip. A hole’s Deck[1] Base = "fx:holeLength-(massLength(ppvKG(36153.16,156036.286,4.0,1140,1.6),0.82))" writes to the deckBaseFormula[1] column verbatim and reconstitutes on import. The evaluated metres land in the deckBase[1] column.
Editing the evaluated number in CSV does not re-trigger the formula. The imported number wins until the next “Apply Charge Rule” runs.
In the Mass field (v1.0.271+) and rule-template mass slot (v1.0.273+), PPV examples #1–#7 collapse to:
Deck[2] Type = COUPLED (ANFO) Deck[2] Top =
fx:deckBase[1]Deck[2] Base =fx:holeLengthDeck[2] Mass =fx:ppvKG(36153.16,156036.286,4,1140,1.6)
— no massLength wrapping, no arithmetic in the stem. The stem deck above auto-scales to fill the remainder when its Scaling Mode is set to VR (Variable). On product swap, the Mass cell shows the evaluated kg as a plain number so the user can edit it directly, or re-enter fx: to restore the formula.
sdobKg)The sdobKg function is the inverse of sdobStem — it returns the deck mass that achieves a target SDoB at the current hole length and diameter. Combined with ppvKG (which returns PPV-allowable mass), this gives the cleanest production-grade form: both constraints expressed as masses in one Mass-field expression.
Deck[1] Type = INERT (Stemming), Top =
0, Base = (VR Variable scaling — auto-fills above charge) Deck[2] Type = COUPLED (ANFO) Deck[2] Top =fx:deckBase[1]Deck[2] Base =fx:holeLengthDeck[2] Mass =fx:Math.min(ppvKG(36153.16,156036.286,4,1140,1.6),sdobKg(1.4,"ANFO"))
Description: “Use the smaller of (a) the PPV-allowable mass for 4 mm/s at the monitor, or (b) the mass that gives an SDoB of 1.4 with ANFO.” Both constraints checked per-hole — every hole gets the more conservative limit automatically. The stem deck above auto-fills the remainder (set its Scaling Mode to VR, no formula needed).
Deck[2] Mass =
fx:sdobKg(1.5,"ANFO")
Description: Sets the charge mass to whatever delivers a Chiappetta SDoB of 1.5 at this hole. Equivalent to the older Stem Base form fx:sdobStem(1.5,"ANFO") but expressed in kg instead of stem length. Use whichever side of the equation makes the design intent clearer.
Deck[2] Mass =
fx:Math.round(sdobKg(1.5,"ANFO")/5)*5
Description: Rounds the SDoB-target mass to the nearest 5 kg — useful when loading is hand-weighed or the truck dispenses in fixed increments. Use Math.ceil(... / 5) * 5 if you must never under-charge.
deckDensity[N] (v1.0.272+)When one rule has to cover multiple products (e.g. a deck that swaps from ANFO → Emulsion in wet holes), hard-coding "ANFO" in the formula breaks the moment the swap fires. The fix: reference the deck’s own density via the indexed variable deckDensity[N]. The formula then adapts automatically — same expression, any product.
Deck[1] Type = INERT (Stemming), Top =
0, Base = (VR — auto-fills above charge) Deck[2] Type = COUPLED (ANFO, with swap ruleswap:w{Emulsion}) Deck[2] Top =fx:deckBase[1]Deck[2] Length =fx:massLength(ppvKG(36153.16,156036.286,4,1140,1.6), deckDensity[2])Deck[2] Base = (derived from Top + Length)
Description: massLength’s second argument is deckDensity[2] — whatever the actual product on Deck 2 happens to be at the moment the formula evaluates. In a wet hole the swap fires (ANFO → Emulsion), deckDensity[2] flips from 0.82 to 1.15, and the charge length shrinks accordingly to hold the same PPV-allowed kg. No second formula needed for the wet case.
Deck[2] Mass =
fx:sdobKg(1.4, deckDensity[2])
Description: SDoB-compliant deck mass for whatever product Deck 2 currently has. Same single formula serves ANFO, Emulsion, gassed emulsion, etc.
Deck[1] Type = INERT (Stemming), Top =
0Deck[1] Base =fx:Math.max(holeLength - massLength(ppvKG(36153.16,156036.286,4,1140,1.6), deckDensity[2]), 2.5)Deck[2] Type = COUPLED (ANFO withswap:w{Emulsion}) Deck[2] Top =fx:deckBase[1]Deck[2] Base =fx:holeLength
Description: The PPV-aware stem-base formula uses Deck 2’s actual density. ANFO holes → longer charge → shorter stem. Emulsion holes (wet, after swap) → denser, so shorter charge for same kg → longer stem. One rule, two products, both PPV-compliant.
deckDensity[N] and chargeDensity[N] are pre-populated for every deck before the layout loop runs, so any deck’s formula can reference any other deck’s density regardless of position-resolution order. Deck 1’s base formula can use deckDensity[2] even though Deck 2 isn’t laid out yet.
This differs from position-indexed vars (deckBase[N], deckTop[N], chargeBase[N], etc.) — those still resolve sequentially because they depend on previously-resolved depths. A formula on Deck 1 cannot reliably reference deckBase[2] (it’s still 0 at that point), but deckDensity[2] is fine.
Rule of thumb: densities are stable, positions cascade.
Kirra is an open-source blasting pattern design application built by Brent Buffham as a gift to the open-cut blasting industry. The Deck Builder formula engine described here is one of several systems — alongside surface meshing, timing analysis, and harness-wire bake — that aim to put genuinely capable design tools into engineers’ hands without six-figure license fees.
If this guide saved you time, consider supporting development at buymeacoffee.com/kirradesign.
— Brent Buffham, Kirra-Design