feat(2): Assignment 2

src/GpuParticleSystem.cpp

@@ -1,6 +1,9 @@
 
 #include "GpuApplication.h"
 
+#define BOUNDARY 0.9f
+#define PUSBACK 0.05f
+
 GpuParticleSystem::GpuParticleSystem(std::string kernelFile) {
 	this->kernelFile = kernelFile;
 	srand(0);
@@ -78,6 +81,10 @@ void GpuParticleSystem::InitPosVel() {
 	// --------------
 	// Your code here
 	// Initialize positions and velocities so that the particles start off on the left side of the screen.
+	for (int i = 0; i < nrParticles; i++) {
+		positions[i * 2] = -BOUNDARY + PUSBACK;
+		positions[i * 2 + 1] = -BOUNDARY + PUSBACK + (2 * BOUNDARY - 2 * PUSBACK) * i / nrParticles;
+	}
 	// --------------
 }
 
@@ -88,6 +95,16 @@ void GpuParticleSystem::Run() {
 	// --------------
 	// Your code here
 	// Setup OpenCL so that the 'updateParticles' kernel can be executed for every frame in the loop below
+	cl::Buffer positions_device(context, CL_MEM_READ_WRITE, sizeof(float) * nrParticles * 2);
+	cl::Buffer velocities_device(context, CL_MEM_READ_WRITE, sizeof(float) * nrParticles * 2);
+
+	cl::KernelFunctor<cl::Buffer, cl::Buffer, float, float, float> kernelFunctor(program, "updateParticles");
+	cl::NDRange rangeGlobal(nrParticles);
+	cl::EnqueueArgs enqueArgs(queue, rangeGlobal);
+
+	// Write initial data to the device buffers.
+	queue.enqueueWriteBuffer(positions_device, CL_TRUE, 0, sizeof(float) * nrParticles * 2, positions.data());
+	queue.enqueueWriteBuffer(velocities_device, CL_TRUE, 0, sizeof(float) * nrParticles * 2, velocities.data());
 	// --------------
 
 	// Setup the OpenGL VBOs that will pass the position and velocity of each particle to the vertex shader
@@ -123,6 +140,9 @@ void GpuParticleSystem::Run() {
 			// --------------
 			// Your code here
 			// Update the OpenCL cl::Buffers holding the positions and velocities
+			printf("Resetting the simulation\n");
+			queue.enqueueWriteBuffer(positions_device, CL_TRUE, 0, sizeof(float) * nrParticles * 2, positions.data());
+			queue.enqueueWriteBuffer(velocities_device, CL_TRUE, 0, sizeof(float) * nrParticles * 2, velocities.data());
 			// --------------
 			reset = false;
 		}
@@ -131,6 +151,19 @@ void GpuParticleSystem::Run() {
 		// Your code here
 		// Update the particles' position and velocities using the OpenCL kernel
 		// Make sure that the OpenGL VBOs are updated with these new values (hint: glBindBuffer, glBufferSubData )
+
+		// Launch the kernel
+		cl::Event event = kernelFunctor(enqueArgs, positions_device, velocities_device, dt, cursorX, cursorY);
+
+		// Read the data from the device buffer into the host vector
+		queue.enqueueReadBuffer(positions_device, CL_TRUE, 0, sizeof(float) * nrParticles * 2, positions.data());
+		queue.enqueueReadBuffer(velocities_device, CL_TRUE, 0, sizeof(float) * nrParticles * 2, velocities.data());
+
+		// Update the OpenGL VBOs
+		glBindBuffer(GL_ARRAY_BUFFER, VBOs[0]);
+		glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(float) * nrParticles * 2, positions.data());
+		glBindBuffer(GL_ARRAY_BUFFER, VBOs[1]);
+		glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(float) * nrParticles * 2, velocities.data());
 		// --------------
 
 		// render to screen

src/ParticleSystem.cl

@@ -5,7 +5,7 @@
 // -------------------------------------
 
 void kernel updateParticles(global float* positions, global float* velocities, float dt, float cursorX, float cursorY) {
-	
+
 	// feel free to play with these values
 	float particleRepulsionRadius = 0.1f;
 	float particleRepulsionStrength = 10.0f;
@@ -14,4 +14,93 @@ void kernel updateParticles(global float* positions, global float* velocities, f
 	float damping = 0.96f;
 
 	// Your code here
+	const float boundary = 0.9f;
+	const float pushback = 0.05f;
+	const float boundaryScale = 1 / (boundaryRepulsionRadius * boundaryRepulsionRadius) * boundaryRepulsionStrength;
+	const float particleScale = 1/ particleRepulsionRadius * particleRepulsionStrength;
+	
+	/* 1. Get the index of the current thread, and thus the indices of the current particle in
+	      positions and velocities arrays. */
+	const int particleId = get_global_id(0);
+	const int x = particleId * 2;
+	const int y = particleId * 2 + 1;
+
+	/* 4. The particle should be affected by gravity. Use g = 9.8 m/s^2. */
+	velocities[y] -= 9.8f * dt;
+
+	/* 5. Several repulsion forces should work on the particle. Note however, that force = m * a,
+	      but we neglect mass here, so instead of applying N forces on the particle, we apply N
+		  acceleration vectors, which, when all summed up change the velocities (using dt). */
+	/* 5.1. The particle should stay within the boundary box. */
+	// When a particle crosses a boundary, it should be teleported back to the correct side of the
+	//  boundary, and the velocity along this axis should be reset to 0.
+	if (positions[x] < -boundary) {
+		positions[x] = -boundary + pushback;
+		velocities[x] = 0;
+	} else if (positions[x] > boundary) {
+		positions[x] = boundary - pushback;
+		velocities[x] = 0;
+	}
+	if (positions[y] < -boundary) {
+		positions[y] = -boundary + pushback;
+		velocities[y] = 0;
+	} else if (positions[y] > boundary) {
+		positions[y] = boundary - pushback;
+		velocities[y] = 0;
+	}
+	// Secondly, if a particle is within boundaryRepulsionRadius of a boundary, a repulsion force
+	//  should be added, pointed away from the boundary. The acceleration should increase according
+	// to a parabole. (f(x) = x^2)
+	if (positions[x] < -boundary + boundaryRepulsionRadius) {
+		float pos = -boundary + boundaryRepulsionRadius - positions[x];
+		velocities[x] += boundaryScale * pos * pos * dt;
+	} else if (positions[x] > boundary - boundaryRepulsionRadius) {
+		float pos = positions[x] - boundary + boundaryRepulsionRadius;
+		velocities[x] -= boundaryScale * pos * pos * dt;
+	}
+	if (positions[y] < -boundary + boundaryRepulsionRadius) {
+		float pos = -boundary + boundaryRepulsionRadius - positions[y];
+		velocities[y] += boundaryScale * pos * pos * dt;
+	} else if (positions[y] > boundary - boundaryRepulsionRadius) {
+		float pos = positions[y] - boundary + boundaryRepulsionRadius;
+		velocities[y] -= boundaryScale * pos * pos * dt;
+	}
+	/* 5.2. The particle should be repelled from other particles within repulsionRadius. Similarly
+		    to the previous point, you can use repulsionRadius and repulsionStrength. Instead of a
+			parabole, you can simply make the norm of the acceleration vector increase linearly
+			with closeness to the other particle. */
+	for (int i = 0; i < get_global_size(0); i++) {
+		if (i == particleId) {
+			continue;
+		}
+		float dx = positions[x] - positions[i * 2];
+		float dy = positions[y] - positions[i * 2 + 1];
+		float dist = sqrt(dx * dx + dy * dy);
+		if (dist < particleRepulsionRadius) {
+			float scale = particleScale * (particleRepulsionRadius - dist) / dist;
+			velocities[x] += scale * dx * dt;
+			velocities[y] += scale * dy * dt;
+		}
+	}
+	/* 5.3. The particle should be repelled from the cursor. You can reuse boundaryRepulsionRadius
+		    and boundaryRepulsionStrength. */
+	float dx = positions[x] - cursorX;
+	float dy = positions[y] - cursorY;
+	float dist = sqrt(dx * dx + dy * dy);
+	if (dist < boundaryRepulsionRadius) {
+		float scale = boundaryScale * (boundaryRepulsionRadius - dist) / dist;	
+		velocities[x] += scale * dx * dt;
+		velocities[y] += scale * dy * dt;
+	}
+
+	/* 3. Just before this, the velocity should be dampened as follows: */
+	velocities[x] *= damping;
+	velocities[y] *= damping;
+
+	/* 2. At the end of this function, the position of the particle should be updated using its
+	      velocity and dt (= the duration of 1 frame, in seconds). Hopefully you still remember how
+		  to update a position based on the velocity, and the velocity based on the acceleration,
+		  and a small timestep (dt). */
+	positions[x] += velocities[x] * dt;
+	positions[y] += velocities[y] * dt;
 }