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	tdetermine bond total tension/compression and tension/compression rate - slider…
	git clone git://src.adamsgaard.dk/slidergrid
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	---
	commit 4d51c127fcf39c33d6a85637b5cb51b321fe320a
	parent 1cbb23226d339f3e3ef3d13fef3ab0141148fcbe
	Author: Anders Damsgaard <[email protected]>
	Date: Wed, 16 Mar 2016 10:56:21 -0700

	determine bond total tension/compression and tension/compression rate

	Diffstat:
	M slider.c \| 31 +++++++++++++++++++++++++++++…
	M slider.h \| 5 +++--
	M vector_math.c \| 5 +++++
	M vector_math.h \| 1 +

	4 files changed, 38 insertions(+), 4 deletions(-)
	---
	diff --git a/slider.c b/slider.c
	t@@ -62,12 +62,17 @@ void update_kinematics(slider s, Float dt, long int iterat…
	}

	// Find the relative displacement and velocity between two sliders
	-void slider_displacement(slider s1, const slider s2, const Float dt)
	+void slider_displacement(slider s1, const slider s2, const Float dt, const int…
	{

	+ // vector pointing from neighbor (s2) position to this slider position (s1)
	const Float3 dist = subtract_float3(s1.pos, s2.pos);
	+
	+ // length of inter-slider vector
	const Float dist_norm = norm_float3(dist);

	+ // unit vector pointing from neighbor (s2) to slider s1
	+ const Float3 n = divide_float3_scalar(dist, dist_norm);

	// relative contact interface velocity w/o rolling
	const Float3 vel_linear = subtract_float3(s1.vel, s2.vel);
	t@@ -80,12 +85,34 @@ void slider_displacement(slider s1, const slider s2, const…
	multiply_scalar_float3(dist_norm/2.,
	cross_float3(dist, s2.angvel))));

	+ // Normal component of the relative contact interface velocity
	+ const Float vel_n = multiply_scalar_float3(-1.0, dot_float3(vel_linear, n)…
	+
	+ // Tangential component of the relative contact interface velocity
	+ // Hinrichsen and Wolf 2004, eq. 13.9
	+ const Float3 = subtract_float3(vel, multiply_float3(n, dot_float3(n, vel))…
	+
	+ // read previous inter-slider distance vector
	+ const Float3 dist0 = s1.neighbor_distance[i];
	+
	+ // increment in inter-slider distance
	+ const Float3 ddist = subtract_float3(dist, dist0);
	+
	+ // save current inter-slider distance
	+ s1.neighbor_distance[i] = dist;
	+
	+ // total relative displacement in inter-slider distance
	+ s1.neighbor_relative_distance_displacement[i] =
	+ add_float3(s1.neighbor_relative_distance_displacement[i], ddist);

	+ // total relative displacement in inter-slider distance
	+ s1.neighbor_relative_distance_velocity[i] = vel_n;

	}


	-// Resolve bond mechanics between a slider and one of its neighbors
	+// Resolve bond mechanics between a slider and one of its neighbors based on t…
	+// incremental linear-elastic model by Potyondy and Cundall 2004


	// Resolve interaction between a slider and all of its neighbors
	diff --git a/slider.h b/slider.h
	t@@ -41,8 +41,9 @@ typedef struct {
	int neighbors[MAX_NEIGHBORS];

	// relative spatial movement between this slider and its neighbors
	- Float3 neighbor_relative_displacement[MAX_NEIGHBORS];
	- Float3 neighbor_relative_contact_velocity[MAX_NEIGHBORS];
	+ Float3 neighbor_distance[MAX_NEIGHBORS];
	+ Float3 neighbor_relative_distance_displacement[MAX_NEIGHBORS];
	+ Float neighbor_relative_distance_velocity[MAX_NEIGHBORS];

	} slider;

	diff --git a/vector_math.c b/vector_math.c
	t@@ -51,6 +51,11 @@ inline Float3 cross_float3(Float3 v1, Float3 v2)
	v1.xv2.y - v1.yv2.x);
	}

	+inline Float dot_float3(Float3 v1, Float3 v2)
	+{
	+ return v1.xv2.x + v1.yv2.y + v1.z*v2.z;
	+}
	+
	// vector-scalar operations
	inline Float3 add_float3_scalar(Float3 v, Float s)
	{
	diff --git a/vector_math.h b/vector_math.h
	t@@ -13,6 +13,7 @@ Float3 subtract_float3(Float3 v1, Float3 v2);
	Float3 multiply_float3(Float3 v1, Float3 v2);
	Float3 divide_float3(Float3 v1, Float3 v2);
	Float3 cross_float3(Float3 v1, Float3 v2);
	+Float dot_float3(Float3 v1, Float3 v2)

	// vector-scalar operations
	Float3 multiply_float3_scalar(Float3 v, Float s);