1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
|
#include "damped.h"
#include "undamped.h"
#include "../../../shared_cpp/Renderer2d.h"
#include "../../../shared_cpp/types.h"
#include "../../../shared_cpp/WebglContext.h"
#include "../../../shared_cpp/mathlib.h"
#include "../../../shared_cpp/MainLoop.h"
#include <cstdio>
#include <cmath>
#include <emscripten/html5.h>
#include <unistd.h>
#include <pthread.h>
#include <cmath>
#include <cfloat>
namespace Damped {
struct DampedSpringWeight {
Mesh2d shape;
float32 radius;
float32 mass = 1.f;
void load(Renderer2d* renderer, float32 inRadius, Vector4 startColor, Vector4 endColor);
void update(float32 dtSeconds);
void render(Renderer2d* renderer);
void unload();
};
struct DampedSpring {
DampedSpringWeight* weight;
Mesh2d shape;
Vertex2d* vertices = NULL;
int32 numSegments = 0;
int32 numVertices = 0;
// Initialization variables
float32 k = 4; // DampedSpring Constant, in N / m (Hooke's Law)
float32 c = 1.f; // Viscous damping coefficient (Damping force)
// Update variables
float32 force = 0.f;
float32 acceleration = 0.f;
float32 velocity = 0.f;
float32 position = 0.f;
void load(Renderer2d* renderer, DampedSpringWeight* inWieight, float32 length, float32 loopRadius, float32 initialDisplacement, float32 inK, float32 inC);
void update(float32 dtSeconds);
void render(Renderer2d* renderer);
void unload();
};
DampedInitVariables initVariables;
void setInitVariables(DampedInitVariables newVariables) { initVariables = newVariables; }
DampedInitVariables getInitVariables() { return initVariables; }
WebglContext* context;
Renderer2d renderer;
MainLoop mainLoop;
DampedSpringWeight weight;
DampedSpring spring;
EM_BOOL onPlayClicked(int eventType, const EmscriptenMouseEvent* mouseEvent, void* userData);
EM_BOOL onStopClicked(int eventType, const EmscriptenMouseEvent* mouseEvent, void* userData);
void load();
void update(float32 deltaTimeSeconds, void* userData);
void unload();
void init(WebglContext* inContext) {
context = inContext;
emscripten_set_click_callback("#gl_canvas_play_damped", NULL, false, onPlayClicked);
emscripten_set_click_callback("#gl_canvas_stop_damped", NULL, false, onStopClicked);
}
void load() {
context->init("#gl_canvas_damped");
renderer.load(context);
weight.load(&renderer, initVariables.mass, Vector4 { 55.f, 235.f, 35.f, 255.f }, Vector4 { 235.f, 5.f, 235.f, 255.f });
spring.load(&renderer, &weight, initVariables.springLength, 16.f, initVariables.initialDisplacement, initVariables.k, initVariables.c);
mainLoop.run(update);
}
void update(float32 deltaTimeSeconds, void* userData) {
// -- Update
spring.update(deltaTimeSeconds);
weight.update(deltaTimeSeconds);
// -- Render
renderer.render();
weight.render(&renderer);
spring.render(&renderer);
}
void unload() {
mainLoop.stop();
renderer.unload();
weight.unload();
spring.unload();
context->destroy();
}
void DampedSpringWeight::load(Renderer2d* renderer, float32 inMass, Vector4 startColor, Vector4 endColor) {
mass = inMass;
radius = mass * 8.f;
if (radius > 42.f) radius = 42.f;
const int32 numSegments = 96;
const float32 radiansPerSegment = (2.f * PI) / static_cast<float>(numSegments);
const int32 numVertices = numSegments * 3;
float32 t = 0.f;
float32 tIncrement = 1.f / (numSegments / 2.f);
startColor = startColor.toNormalizedColor();
endColor = endColor.toNormalizedColor();
Vertex2d vertices[numVertices];
for (int idx = 0; idx < numSegments; idx++) {
int vIdx = idx * 3;
Vector4 color = lerp(startColor, endColor, t);
if (idx >= numSegments / 2) {
t -= tIncrement;
} else {
t += tIncrement;
}
vertices[vIdx].color = color;
vertices[vIdx].position = Vector2 { radius * cosf(radiansPerSegment * idx), radius * sinf(radiansPerSegment * idx) };
vertices[vIdx + 1].color = color;
vertices[vIdx + 1].position = Vector2 { 0.f, 0.f };
vertices[vIdx + 2].color = color;
vertices[vIdx + 2].position = Vector2 { radius * cosf(radiansPerSegment * (idx + 1)), radius * sinf(radiansPerSegment * (idx + 1)) };
}
shape.load(vertices, numVertices, renderer);
}
void DampedSpringWeight::update(float32 dtSeconds) {
}
void DampedSpringWeight::render(Renderer2d* renderer) {
shape.render(renderer);
}
void DampedSpringWeight::unload() {
shape.unload();
}
const float32 epsilon = 0.0001f;
void DampedSpring::load(Renderer2d* renderer, DampedSpringWeight* inWeight, float32 length, float32 loopRadius, float32 initialDisplacement, float32 inK, float32 inC) {
weight = inWeight;
k = inK;
c = inC;
// Set the quadratic terms to something that we're familiar with.
float32 A = weight->mass;
float32 B = c;
float32 C = k;
float32 discriminant = B * B - (4 * A * C);
acceleration = 0;
velocity = 0;
position = initialDisplacement;
if (discriminant < epsilon && discriminant > -epsilon) {
// Real repeated root (~ zero): Critically damped motion
printf("Critically damped motion.\n");
}
else if (discriminant > 0) {
// Two real roots (greater than zero): Overdamped motion
printf("Overdamped motion.\n");
}
else {
// Complex pair (less than zero): Underdamped motion
printf("Underdamped motion.\n");
}
const int32 verticesPerSegment = 6;
numSegments = 256;
numVertices = numSegments * verticesPerSegment;
vertices = new Vertex2d[numVertices];
float32 lengthIncrement = length / static_cast<float32>(numSegments);
const float32 frequency = 0.25f;
const float32 loopWidth = 20.f;
const float32 offset = 0.25f;
int32 vidx = 0;
float32 dx = position;
for (int pidx = 0; pidx < numSegments; pidx++) {
float32 y1 = lengthIncrement * pidx;
float32 x1 = loopWidth * sinf(frequency * y1 + offset);
float32 y2 = y1 + lengthIncrement;
float32 x2 = loopWidth * sinf(frequency * y2 + offset);
float32 y1Offset = dx * (1.f - pidx / static_cast<float32>(numSegments));
float32 y2Offset = dx * (1.f - (pidx + 1) / static_cast<float32>(numSegments));
y1 += y1Offset;
y2 += y2Offset;
vertices[vidx++].position = Vector2(x1, y1);
vertices[vidx++].position = Vector2(x1, y2);
vertices[vidx++].position = Vector2(x2, y1);
vertices[vidx++].position = Vector2(x2, y1);
vertices[vidx++].position = Vector2(x1, y2);
vertices[vidx++].position = Vector2(x2, y2);
}
shape.load(vertices, numVertices, renderer, GL_DYNAMIC_DRAW);
shape.model = Mat4x4().translateByVec2(Vector2(400, 300));
weight->shape.model = shape.model.translateByVec2(Vector2(0, -weight->radius + dx));
}
void DampedSpring::update(float32 dtSeconds) {
force = -weight->mass * acceleration - c * velocity - k * position;
acceleration = (force * dtSeconds) / weight->mass;
velocity = velocity + acceleration * dtSeconds;
float32 lastPosition = position;
position = position + velocity * dtSeconds;
float32 dx = position - lastPosition;
int32 vidx = 0;
for (int pidx = 0; pidx < numSegments; pidx++) {
float32 y1Offset = dx * (1.f - pidx / static_cast<float32>(numSegments));
float32 y2Offset = dx * (1.f - (pidx + 1) / static_cast<float32>(numSegments));
vertices[vidx++].position.y += y1Offset;
vertices[vidx++].position.y += y2Offset;
vertices[vidx++].position.y += y1Offset;
vertices[vidx++].position.y += y1Offset;
vertices[vidx++].position.y += y2Offset;
vertices[vidx++].position.y += y2Offset;
}
weight->shape.model = weight->shape.model.translateByVec2(Vector2(0, dx));
}
void DampedSpring::render(Renderer2d* renderer) {
glBindBuffer(GL_ARRAY_BUFFER, shape.vbo);
glBufferSubData(GL_ARRAY_BUFFER, 0, numVertices * sizeof(Vertex2d), &vertices[0]);
shape.render(renderer);
}
void DampedSpring::unload() {
shape.unload();
delete[] vertices;
}
EM_BOOL onPlayClicked(int eventType, const EmscriptenMouseEvent* mouseEvent, void* userData) {
printf("Play clicked\n");
load();
return true;
}
EM_BOOL onStopClicked(int eventType, const EmscriptenMouseEvent* mouseEvent, void* userData) {
printf("Stop clicked\n");
unload();
return true;
}
}
|
