Hi there!

My current particle system its based on the example: http://content.gpwiki.org/index.php/D3DBook:Dynamic_Particle_Systems

However I have one remaining doubt. During the development I noticed that the particles emission rate its capped at 128 per frame due the memory limits of the geometry stream output. However, I would like to implement a particle system able to handle millions of particles at the same time. This is possible with the current particle system, but I need to wait 130 seconds to reach the millions (using particles with 130 sec lifetime), which is not very optimal.

I was wondering if any of you knows a way to achieve this using the GPU.

Cheers,

José

I don't see any reference that you are pointing to, but can't you just execute the particle injection draw call more than once per frame?

Sorry about that, just updated the post.

The problem its that the particle injection happens inside the geometry shader, so it has a limit of 1024b per emission (that its equal to 128 particles since each one have 8 components)

Cheers

Oh nice now I get what you mean. But in order to do that, wouldn't I need need to separate the Update logic of the particles from the Particle Emission? otherwise the particles will move too fast since I would be executing their update a lot of times per frame.

Thanks for the help and awesome article

PS: I tried to transfer the particle creation to the CPU using a 3rd buffer which appends the new particles to the streamOutput, however right now it doesn't work and I am not quite sure why. If anyone can check it out I would be more than grateful.

FX Code: https://github.com/neroziros/PSDX11/blob/master/ParticleEffect.fx

Class: https://github.com/neroziros/PSDX11/blob/master/Particleclass.cpp

I believe the main problem its here, in the mapping procedure:

Class: https://github.com/neroziros/PSDX11/blob/master/Particleclass.cpp

I hope my code can also help anyone else interested in building a million particle system based on the GPU :) Cheers

    // CPU PARTICLE CREATION
    // Add new particles if they were created
    if (!newParticlesCreated)
    {
        // Map to the buffer and render the new particles to add them to the pipeline
        D3D11_MAPPED_SUBRESOURCE mappedResource;
        PARTICLE_VERTEX* dataPtr;


        m_D3D->GetDeviceContext()->Map(g_pNewParticles, 0, D3D11_MAP_WRITE_DISCARD, 0, &mappedResource);
        dataPtr = (PARTICLE_VERTEX*)mappedResource.pData;


        // Copy the data into the vertex buffer.
        memcpy(dataPtr, (void*)newParticlesArr, (sizeof(PARTICLE_VERTEX)* emissionRate));


        // Unmap the buffer
        m_D3D->GetDeviceContext()->Unmap(g_pNewParticles, 0);


        // Set the buffer as the input
        pBuffers[0] = g_pNewParticles;
        UINT stride[1] = { sizeof(PARTICLE_VERTEX) };
        UINT offset[1] = { 0 };
        m_D3D->GetDeviceContext()->IASetVertexBuffers(0, 1, pBuffers, stride, offset);
        m_D3D->GetDeviceContext()->IASetPrimitiveTopology(D3D11_PRIMITIVE_TOPOLOGY_POINTLIST);


        // Point to the correct output buffer
        pBuffers[0] = g_pParticleStreamTo;
        m_D3D->GetDeviceContext()->SOSetTargets(1, pBuffers, offset);


        // Draw the buffers
        D3DX11_TECHNIQUE_DESC techDesc;
        g_pAdvanceParticles->GetDesc(&techDesc);
        for (UINT p = 0; p < techDesc.Passes; ++p)
        {
            g_pAdvanceParticles->GetPassByIndex(p)->Apply(0, m_D3D->GetDeviceContext());
            m_D3D->GetDeviceContext()->DrawAuto();
        }


        // Get back to normal
        pBuffers[0] = NULL;
        m_D3D->GetDeviceContext()->SOSetTargets(1, pBuffers, offset);


        // Free the particle array memory
        delete (newParticlesArr);


        // Reset variables
        newParticlesCreated = false;
    }

Hi there, I managed to do as suggested and separated the emission logic from the update logic. Feel free to check the code here:

https://github.com/neroziros/PARTICLESYSTEM/

Now the problem its that I can only reach around 460800 particles before the fps start to drop too low (around 25-35 fps). I have a Phenom II X6 & NVIDIA 560GTX.

This is probably an optimization problem, any suggestion its welcomed.

Cheers!