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#include "../../../shared_cpp/Renderer2d.h"
#include "../../../shared_cpp/types.h"
#include "../../../shared_cpp/mathlib.h"
#include <cstdio>
#include <math.h>
Vector2 GRAVITY_ACCELERATION = Vector2(0, -100.f);
struct PointMassUpdateData {
int32 index = 0;
Vector2 localPosition; // Position is in world coordinates
Vector2 worldPosition; // Position is in world coordinates
Vector2 acceleration;
Vector2 velocity;
Vector2 force;
bool isHovered = false;
PointMassUpdateData* neighbors[4];
};
struct SoftbodyRectangle {
// User defined
float32 width = 200;
float32 height = 200;
int32 springDensity = 16;
float32 k = 8000.f; // in N /m
float32 c = 30.f;
float32 jointMassKg = 1.f;
float32 floorPosition = 200;
// Calculated before runtime
Vector2 springDimensions;
// Runtime data
Vector2 velocity;
Vector2 worldPosition;
PointMassUpdateData* updateData = NULL;
float32 rotationalVelocity = 0.f;
float32 rotation = 0.f;
// Render data
Mesh2d mesh;
Mesh2d pointsMesh;
Mesh2d floorMesh;
Vertex2d* vertices = NULL;
Vertex2d* pointsVertices = NULL;
void load(Renderer2d* renderer) {
velocity = Vector2(0, 0);
worldPosition = Vector2(800.f / 2 - width / 2, 400.f);
springDimensions = Vector2(width / springDensity, height / springDensity);
int32 numVertices = springDensity * springDensity; // Each subdivision is a square.
int32 numIndices = 6 * ((springDensity - 1) * (springDensity - 1));
vertices = new Vertex2d[numVertices];
updateData = new PointMassUpdateData[numVertices];
pointsVertices = new Vertex2d[numVertices];
auto indices = new GLuint[numIndices];
// -- Load a square with the desired density
int32 vIdx = 0;
int32 iIdx = 0;
float32 inverseDensity = 1.f / springDensity;
float32 halfInv = inverseDensity / 2.f;
for (int32 y = 0; y < springDensity; y++) { // Rows
for (int32 x = 0; x < springDensity; x++) { // Columns
Vector2 vpos = Vector2(x * inverseDensity - halfInv, y * inverseDensity- halfInv);
// Get the position in mode coordinates
vpos.x = vpos.x * width;
vpos.y = vpos.y * height;
updateData[vIdx].localPosition = vpos;
// Get the position in world coorodinates
vpos.x = vpos.x + worldPosition.x;
vpos.y = vpos.y + worldPosition.y;
vertices[vIdx] = { vpos, Vector4(1, 0, 0, 1) };
updateData[vIdx].index = vIdx;
updateData[vIdx].worldPosition = vpos;
updateData[vIdx].force = Vector2(0, 0);
updateData[vIdx].velocity = Vector2(0, 0);
updateData[vIdx].acceleration = Vector2(0, 0);
if (x != springDensity - 1) updateData[vIdx].neighbors[0] = &updateData[vIdx + 1]; // Right
else updateData[vIdx].neighbors[0] = NULL;
if (y != springDensity - 1) updateData[vIdx].neighbors[1] = &updateData[vIdx + springDensity]; // Bottom
else updateData[vIdx].neighbors[1] = NULL;
if (x != 0) updateData[vIdx].neighbors[2] = &updateData[vIdx - 1]; // Left
else updateData[vIdx].neighbors[2] = NULL;
if (y != 0) updateData[vIdx].neighbors[3] = &updateData[vIdx - springDensity]; // Top
else updateData[vIdx].neighbors[3] = NULL;
if (y != springDensity - 1 && x != springDensity - 1) {
indices[iIdx++] = vIdx;
indices[iIdx++] = vIdx + 1;
indices[iIdx++] = vIdx + springDensity;
indices[iIdx++] = vIdx + springDensity;
indices[iIdx++] = vIdx + springDensity + 1;
indices[iIdx++] = vIdx + 1;
}
pointsVertices[vIdx].position = vpos;
pointsVertices[vIdx].color = Vector4(0, 0, 0, 1);
vIdx++;
}
}
mesh.load(vertices, numVertices, indices, numIndices, renderer, GL_DYNAMIC_DRAW);
pointsMesh.load(pointsVertices, numVertices, renderer, GL_DYNAMIC_DRAW);
delete [] indices;
// -- Load the floor line;
Vector2 floorDimensions = Vector2(renderer->context->width, 8);
Vector4 floorColor = Vector4(0.5, 0.5, 0.5, 1);
Vertex2d floorVertices[6];
floorVertices[0] = { Vector4(0, floorPosition, 0, 1), floorColor };
floorVertices[1] = { Vector4(floorDimensions.x, floorPosition, 0, 1), floorColor };
floorVertices[2] = { Vector4(0, floorPosition - floorDimensions.y, 0, 1), floorColor };
floorVertices[3] = { Vector4(0, floorPosition - floorDimensions.y, 0, 1), floorColor };
floorVertices[4] = { Vector4(floorDimensions.x, floorPosition - floorDimensions.y, 0, 1), floorColor };
floorVertices[5] = { Vector4(floorDimensions.x, floorPosition, 0, 1), floorColor };
floorMesh.load(floorVertices, 6, renderer);
}
Vector2 getForceBetweenPointMasses(PointMassUpdateData* first, PointMassUpdateData* second) {
const float32 EPSILON = 0.1f;
auto relativeVelocity = second->velocity - first->velocity;
auto restLength = (second->localPosition - first->localPosition).length();
auto relativePosition = second->worldPosition - first->worldPosition;
auto currentLength = relativePosition.length();
auto positionDir = relativePosition.normalize();
auto velDotProduct = positionDir.dot(relativeVelocity);
auto lengthDifference = (currentLength - restLength);
if (ABS(lengthDifference) < EPSILON) {
lengthDifference = 0;
}
float32 springForce = k * lengthDifference;
float32 dampingForce = c * velDotProduct;
float32 totalForce = springForce + dampingForce;
return positionDir * totalForce;
}
void update(float32 dtSeconds) {
// -- Apply all forces
for (int32 v = 0; v < pointsMesh.numVertices; v++) {
auto pointMass = &updateData[v];
pointMass->force += GRAVITY_ACCELERATION * jointMassKg;
// -- Add the forces from it's neighbors. Note that we only do the first two
// neighbors, which are the right and bottom neighbors.
for (int32 n = 0; n < 4; n++) {
auto neighbor = pointMass->neighbors[n];
if (neighbor == NULL) continue;
auto forceBetween = getForceBetweenPointMasses(pointMass, neighbor);
pointMass->force = pointMass->force + forceBetween;
}
}
// -- Calculate the rotation of the entire body
//rotationalVelocity = 0.1f;
//auto gravityDt = GRAVITY_ACCELERATION * dtSeconds;
//velocity = velocity + gravityDt;
//worldPosition = worldPosition + (velocity * dtSeconds);
// -- Euler integrate and update the local position of each vertex.
for (int32 v = 0; v < pointsMesh.numVertices; v++) {
auto pointMass = &updateData[v];
// -- Euler integration to find the current velocity and position
pointMass->acceleration = pointMass->force / jointMassKg;
pointMass->velocity = pointMass->velocity + (pointMass->acceleration * dtSeconds);
pointMass->worldPosition = pointMass->worldPosition + (pointMass->velocity * dtSeconds);
// pointMass->restingPosition = pointMass->restingPosition.rotateAround(rotationalVelocity * dtSeconds, modelPosition);
// pointMass->currentPosition = pointMass->currentPosition.rotateAround(rotationalVelocity * dtSeconds, modelPosition);
vertices[v].position = pointMass->worldPosition;
pointsVertices[v].position = pointMass->worldPosition;
pointMass->force = Vector2(); // Reset the force for the next update
}
// -- Collision detection
for (int32 v = 0; v < pointsMesh.numVertices; v++) {
auto pointMass = &updateData[v];
auto prevPos = pointMass->worldPosition;
// -- Floor
particleFloorCollision(pointMass, prevPos, dtSeconds);
//
const float32 COLLISION_DISTANCE = 0.3f;
// auto localVector = pointMass->worldPosition - worldPosition;
// auto displacement = (pointMass->worldPosition - worldPosition) - pointMass->localPosition;
// if (displacement.length() >= 20.f) {
// // auto positionNormal = (pointMass->restingPosition - pointMass->currentPosition).normalize();
// // pointMass->currentPosition = pointMass->restingPosition - positionNormal * COLLISION_DISTANCE;
// // float32 dotProduct = pointMass->velocity.dot(positionNormal);
// // pointMass->velocity = pointMass->velocity - positionNormal * (2 * dotProduct);
// }
for (int32 n = 0; n < 4; n++) {
auto neighbor = pointMass->neighbors[n];
if (neighbor == NULL) continue;
if ((neighbor->worldPosition - pointMass->worldPosition).length() < COLLISION_DISTANCE) {
auto positionNormal = (neighbor->worldPosition - pointMass->worldPosition).normalize();
pointMass->worldPosition = neighbor->worldPosition - positionNormal * COLLISION_DISTANCE;
float32 dotProduct = pointMass->velocity.dot(positionNormal);
pointMass->velocity = pointMass->velocity - positionNormal * (2 * dotProduct);
}
}
}
// -- Update vertices
mesh.updateVertices(vertices);
pointsMesh.updateVertices(pointsVertices);
}
void particleFloorCollision(PointMassUpdateData* ud, Vector2 prevPos, float32 dtSeconds) {
// We assume that the floor is always horizontal for this simulation
auto dotProduct = ud->velocity.dot(Vector2(0, 1));
// if (dotProduct >= 0) {
// return; // Not moving in the same direction
// }
if (ud->worldPosition.y - floorPosition < 0.1f) {
ud->worldPosition.y = floorPosition - 0.1f;;
ud->velocity = (ud->velocity - Vector2(0, 1) * (2 * dotProduct)) * 0.5f;
}
}
void render(Renderer2d* renderer) {
mesh.render(renderer);
pointsMesh.render(renderer, GL_POINTS);
floorMesh.render(renderer);
}
void unload() {
mesh.unload();
pointsMesh.unload();
delete [] vertices;
delete [] pointsVertices;
}
};
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