[arrayfire] 63/284: initial gravity example

[Ghislain Vaillant]

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ghisvail-guest pushed a commit to branch debian/experimental
in repository arrayfire.

commit cad4c2c67c2d34777155a1007f5309cde904a983
Author: syurkevi <stefan at arrayfire.com>
Date:   Wed Dec 9 02:06:35 2015 -0500

    initial gravity example
---
 examples/graphics/gravity_sim.cpp | 126 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 126 insertions(+)

diff --git a/examples/graphics/gravity_sim.cpp b/examples/graphics/gravity_sim.cpp
new file mode 100644
index 0000000..77f662f
--- /dev/null
+++ b/examples/graphics/gravity_sim.cpp
@@ -0,0 +1,126 @@
+/*******************************************************
+ * Copyright (c) 2014, ArrayFire
+ * All rights reserved.
+ *
+ * This file is distributed under 3-clause BSD license.
+ * The complete license agreement can be obtained at:
+ * http://arrayfire.com/licenses/BSD-3-Clause
+ ********************************************************/
+
+#include <arrayfire.h>
+#include <iostream>
+#include <cstdio>
+
+using namespace af;
+using namespace std;
+
+static const int width = 512, height = 512;
+
+
+void simulate(af::array &parts, af::array &vels, af::array &forces){
+    parts += vels;
+
+    //calculate distance to center
+    float center_coors[2]   = { width / 2, height / 2 };
+    af::array col  = tile(af::array(1, 2, center_coors), parts.dims(0));
+    af::array diff = parts - col;
+    af::array dist = sqrt( diff.col(0)*diff.col(0) + diff.col(1)*diff.col(1) );
+
+    forces = -1 * diff;
+    forces.col(0) /= dist; //normalize force vectors
+    forces.col(1) /= dist; //normalize force vectors
+
+    //update velocities from forces
+    vels += forces;
+
+}
+
+void collisions(af::array &parts, af::array &vels){
+    //clamp particles inside screen border
+    parts.col(0) = min(width, max(0, parts.col(0)));
+    parts.col(1) = min(height - 1, max(0, parts.col(1)));
+
+    //calculate distance to center
+    float center_coors[2]   = { width / 2, height / 2 };
+    af::array col  = tile(af::array(1, 2, center_coors), parts.dims(0));
+    af::array diff = parts - col;
+    af::array dist = sqrt( diff.col(0)*diff.col(0) + diff.col(1)*diff.col(1) );
+
+    /*
+    //collide with center sphere
+    int radius = 50;
+    af::array col_ids = dist(dist<radius);
+    if(col_ids.dims(0) > 0) {
+        //vels(col_ids, span) += -1 * parts(col_ids, span);
+        vels(col_ids, span) = 0;
+    }
+    */
+
+}
+
+int main(int argc, char *argv[])
+{
+    try {
+        const static int total_particles=200;
+        static const int reset = 500;
+
+        af::info();
+
+        af::Window myWindow(width, height, "Gravity Simulation using ArrayFire");
+
+        int frame_count = 0;
+
+        // Initialize the kernel array just once
+        const af::array draw_kernel = gaussianKernel(3, 3);
+
+        // Generate a random starting state
+        af::array particles = af::randu(total_particles,2);
+        particles.col(0) *= width;
+        particles.col(1) *= height;
+
+        af::array velocities = af::randn(total_particles, 2);
+        af::array forces = af::randn(total_particles, 2);
+
+        af::array image = af::constant(0, width, height);
+        af::array ids(total_particles, u32);
+
+        while(!myWindow.close()) {
+
+            ids = (particles.col(0).as(u32) * height) + particles.col(1).as(u32);
+            image(ids) += 255;
+            image = convolve2(image, draw_kernel);
+            myWindow.image(image);
+            image(span, span) = 0;
+            frame_count++;
+
+            // Generate a random starting state
+            if(frame_count % reset == 0) {
+                particles = af::randu(total_particles,2);
+                particles.col(0) *= width;
+                particles.col(1) *= height;
+
+                velocities = af::randn(total_particles, 2);
+            }
+
+            //run force simulation and update particles
+            simulate(particles, velocities, forces);
+
+            //check for collisions and adjust velocities accordingly
+            collisions(particles, velocities);
+
+        }
+    } catch (af::exception& e) {
+        fprintf(stderr, "%s\n", e.what());
+        throw;
+    }
+
+    #ifdef WIN32 // pause in Windows
+    if (!(argc == 2 && argv[1][0] == '-')) {
+        printf("hit [enter]...");
+        fflush(stdout);
+        getchar();
+    }
+    #endif
+    return 0;
+}
+

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