Granular.jl

commit 0ca0e4abf901666fd3795f8b126be72e52645352
parent 026453ac365e0acd332634c91088f60639517aec
Author: Anders Damsgaard <andersd@riseup.net>
Date:   Thu, 21 Dec 2017 14:57:50 -0500

Put contact check into dedicated and reusable function

Diffstat:
M
src/contact_search.jl
 | 
55
+++++++++++++++++++++++++++++++++++++++++++++++++++++++

1 file changed, 55 insertions(+), 0 deletions(-)
diff --git a/src/contact_search.jl b/src/contact_search.jl
@@ -145,6 +145,61 @@ function findContactsInGrid!(simulation::Simulation, grid::Any)
     nothing
 end
 
+
+export checkForContacts
+"""
+    checkForContacts(grid, position, radius)
+
+Perform an O(n*log(n)) cell-based contact search between a candidate grain with
+position `position` and `radius`, against all grains registered in the `grid`.
+Returns `true` if no contacts were found, and `false` if contacts were found.
+
+# Arguments
+* `grid::Any`: `Ocean` or `Atmosphere` grid containing sorted particles.
+* `position::Vector{Float64}`: Candidate center position to probe for contacts
+    with existing grains [m].
+* `radius::Float64`: Candidate radius [m].
+"""
+function checkForContacts(grid::Any, x_candidate::Vector{Float64},
+                          r_candidate::Float64)
+
+    sw = zeros(2); se = zeros(2); ne = zeros(2); nw = zeros(2)
+    distance_modifier = zeros(2)
+    no_overlaps_found = true
+
+    # Inter-grain position vector and grain overlap
+    ix, iy = findCellContainingPoint(grid, x_candidate, sw, se, ne, nw)
+
+    # Check for overlap with existing grains
+    for ix_=(ix - 1):(ix + 1)
+        for iy_=(iy - 1):(iy + 1)
+
+            # correct indexes if necessary
+            ix_corrected, iy_corrected =
+                periodicBoundaryCorrection!(grid, ix_, iy_, distance_modifier)
+
+            # skip iteration if target still falls outside grid after
+            # periodicity correction
+            if ix_corrected < 1 || ix_corrected > nx ||
+                iy_corrected < 1 || iy_corrected > ny
+                continue
+            end
+
+            @inbounds for idx in grid.grain_list[ix_corrected, iy_corrected]
+                if norm(simulation.grains[idx].lin_pos - x_candidate +
+                    distance_modifier) -
+                    (simulation.grains[idx].contact_radius +
+                     r_candidate) < 0.
+
+                    no_overlaps_found = false
+                    break  # overlap: skip this candidate
+                end
+            end
+        end
+    end
+    return no_overlaps_found
+end
+
 """
     periodicBoundaryCorrection!(grid::Any, i::Integer, j::Integer,
                                 i_corrected::Integer, j_corrected::Integer,