ParticleRenderer.cpp

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/* Copyright (C) 2011 Wildfire Games.
 * This file is part of 0 A.D.
 *
 * 0 A.D. is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * 0 A.D. is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "precompiled.h"

#include "ParticleRenderer.h"

#include "graphics/ParticleEmitter.h"
#include "graphics/ShaderManager.h"
#include "graphics/TextureManager.h"
#include "ps/Profile.h"
#include "renderer/Renderer.h"

struct ParticleRendererInternals
{
    CShaderTechniquePtr shader;
    CShaderTechniquePtr shaderSolid;
    std::vector<CParticleEmitter*> emitters;
};

ParticleRenderer::ParticleRenderer()
{
    m = new ParticleRendererInternals();
}

ParticleRenderer::~ParticleRenderer()
{
    delete m;
}

void ParticleRenderer::Submit(CParticleEmitter* emitter)
{
    m->emitters.push_back(emitter);
}

void ParticleRenderer::EndFrame()
{
    m->emitters.clear();
    // this should leave the capacity unchanged, which is okay since it
    // won't be very large or very variable
}

struct SortEmitterDistance
{
    SortEmitterDistance(const CMatrix3D& m) : worldToCam(m) { }

    // TODO: if this is slow, we should pre-compute the distance for each emitter

    bool operator()(CParticleEmitter* const& a, CParticleEmitter* const& b)
    {
        CVector3D posa = a->GetPosition();
        CVector3D posb = b->GetPosition();
        if (posa == posb)
            return false;
        float dista = worldToCam.Transform(posa).LengthSquared();
        float distb = worldToCam.Transform(posb).LengthSquared();
        return distb < dista;
    }

    CMatrix3D worldToCam;
};

void ParticleRenderer::PrepareForRendering(const CShaderDefines& context)
{
    PROFILE3("prepare particles");

    // Can't load the shader in the constructor because it's called before the
    // renderer initialisation is complete, so load it the first time through here
    if (!m->shader)
    {
        // Only construct the shaders when shaders are supported and enabled; otherwise
        // RenderParticles will never be called so it's safe to leave the shaders as null
        if (g_Renderer.GetRenderPath() == CRenderer::RP_SHADER)
        {
            m->shader = g_Renderer.GetShaderManager().LoadEffect(str_particle, context, CShaderDefines());
            m->shaderSolid = g_Renderer.GetShaderManager().LoadEffect(str_particle_solid, context, CShaderDefines());
        }
    }

    {
        PROFILE("update emitters");
        for (size_t i = 0; i < m->emitters.size(); ++i)
        {
            CParticleEmitter* emitter = m->emitters[i];
            emitter->UpdateArrayData();
        }
    }

    {
        // Sort back-to-front by distance from camera
        PROFILE("sort emitters");
        CMatrix3D worldToCam;
        g_Renderer.GetViewCamera().m_Orientation.GetInverse(worldToCam);
        std::stable_sort(m->emitters.begin(), m->emitters.end(), SortEmitterDistance(worldToCam));
    }

    // TODO: should batch by texture here when possible, maybe
}

void ParticleRenderer::RenderParticles(bool solidColor)
{
    CShaderTechniquePtr shader = solidColor ? m->shaderSolid : m->shader;

    shader->BeginPass();

    shader->GetShader()->Uniform(str_transform, g_Renderer.GetViewCamera().GetViewProjection());

    if (!solidColor)
        glEnable(GL_BLEND);
    glDepthMask(0);

    for (size_t i = 0; i < m->emitters.size(); ++i)
    {
        CParticleEmitter* emitter = m->emitters[i];

        emitter->Bind(shader->GetShader());
        emitter->RenderArray(shader->GetShader());
    }

    CVertexBuffer::Unbind();

    pglBlendEquationEXT(GL_FUNC_ADD);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

    glDisable(GL_BLEND);
    glDepthMask(1);

    shader->EndPass();
}

void ParticleRenderer::RenderBounds(CShaderProgramPtr& shader)
{
    for (size_t i = 0; i < m->emitters.size(); ++i)
    {
        CParticleEmitter* emitter = m->emitters[i];

        CBoundingBoxAligned bounds = emitter->m_Type->CalculateBounds(emitter->GetPosition(), emitter->GetParticleBounds());
        bounds.Render(shader);
    }
}