docs/handbook/bug_reports/floating_point_error.md

@@ -0,0 +1,45 @@
+# Floating point error
+
+## Explanation
+
+Every time user are operated by non integer values in blender is floating
+point values of 32 bit. Here is some notes about such values:
+
+1.  Order of operations and its type is matter. `A + A + A` is not `A * 3`.
+2.  All floating points values are decimal representation of binary real number
+    and binary exponent value.
+3.  Just like you can not write `10 / 3` in limited decimal number (`3.333...`),
+    you can not represent `1.1` as floating point value without very small but
+    still existed fractional part: `1.10000002384185791015625`.
+4.  Just to do not mess UI by all this, usually not really matter, details,
+    Blender draw floating point values with fixed number of digits after dot.
+3.  Comparison for equality is something that users should not do at all. If
+    this values are not typed by user, but result of calculations, comparison
+    going to be fail in a lot of cases. Sometimes blender can provide epsilon
+    setting to avoid this error.
+4.  Fix of floating point error are not trivial. For example, does this should
+    requers infint number of digits for `3.333...`? Or mathematical expressions
+    should be stored as value and comparison should be kind of subtraction of
+    such expressions and next simplification by mathematical rules be performed?
+5.  Using of dooble will increase execution time, memory usage. Replace of all
+    floating point numbers in blender will be far expensive refactor.
+
+## For bug triaging
+
+Bugs, that related with floating point precision are well defined and can be reported as:
+
+-   Graphical artifacts in shader.
+-   Incorrect result of conditions.
+-   Shaking of objects on large coordinates.
+-   Additional fractional part in result of symmetrical operations.
+-   Logarithmic notation of value in field (`3e-10`).
+
+But even so, this is not a bug. Most often the error is caused by the user or
+can be corrected by changing the math.
+
+## References
+
+Some links to check:
+
+-   More detailed learn about float: <https://en.wikipedia.org/wiki/Floating-point_arithmetic>.
+-   Online view of floating point value representation: <https://www.h-schmidt.net/FloatConverter/IEEE754.html>.

docs/handbook/bug_reports/triaging_playbook.md

@@ -69,6 +69,7 @@ template for them.
 - Complete report, but performance
 - Complete report, but corrupted mesh
 - Complete report, but dependency cycle
+- Complete report, but floating point precision
 - Unsupported graphics card or driver
 - Blender doesn't run / crashes
 
@@ -422,6 +423,35 @@ latest Blender:
 > but these cases are mostly known and the solution for them requires bigger
 > design considerations which is outside of the scope of the bug tracker.
 
+### Complete report, but floating point precision
+
+**Example:** [\#121793](https://projects.blender.org/blender/blender/issues/121793),
+[\#122181](https://projects.blender.org/blender/blender/issues/122181),
+[\#122046](https://projects.blender.org/blender/blender/issues/122046)
+
+**Action:**
+
+- Close the report.
+- Change the `Status >` label to `Status > **Archived**` (a bot
+  should do this automatically - but only visible after a manual refresh
+  of the page).
+
+> NOTE: **Message Example**
+> Thanks for report. Core of the issue described here is the floating point
+> precision issue. Some description of such issues:
+> 
+> 1.  Math in computer is not the same math that you might learn in the school.
+>     There is the set of some limitations and specifics that cause different result
+>     in compare with your expectation.
+> 2.  Range of enough good value precision is around 5 digits around dot.
+> 3.  UI draw only very small range of digits in fractional part just for
+>     compactness. If you want to see real representation of the value, you need
+>     to use python.
+> 4.  Floating point value is how computers handle real number today, and
+>     there is no way to fix issues related with that in general mean.
+>
+> See <https://developer.blender.org/docs/handbook/bug_reports/floating_point_error/> for more details.
+
 ### Unsupported graphics card or driver
 
 **Action:**