renderSystem.cpp

#include "renderSystem.hpp"

constexpr auto const vertCode = R"END(
    #version 430
    struct Particle {
        vec3 color;
        int onFire;
        vec2 pos;
    };

    layout (location = 0) in vec3 vertex;
    layout (location = 0) uniform mat4 pMatrix;
    layout (location = 4) uniform mat4 vMatrix;
    layout (std430, binding = 1) readonly buffer Particle_Buffer {
	    Particle particles[];
    };
    layout (location = 0) flat out vec4 color;

    void main() {
        const vec3 offset = vec3(particles[gl_InstanceID].pos, 0.0);
        gl_Position = pMatrix * vMatrix * vec4((vertex * 0.5) + offset,  1.0);
        color = vec4(mix(particles[gl_InstanceID].color, vec3(1, 0.2F, 0), particles[gl_InstanceID].onFire * 0.75), 1.0F);
    }
)END";

constexpr auto const fragCode = R"END(
    #version 430

    layout (location = 0) flat in vec4 color;
    layout (location = 0) out vec4 fragColor;

    void main() {
        fragColor = color;
    }
)END";

//////////////////////////////////////////////////////////////////////
/// Custom Constructor
//////////////////////////////////////////////////////////////////////

RenderSystem::RenderSystem()
    : m_shader(vertCode, fragCode), m_model({ vec3(-1, -1, 0), vec3(1, -1, 0),
                                              vec3(1, 1, 0), vec3(-1, 1, 0) }),
      m_draw(4, 0, 0, GL_DYNAMIC_STORAGE_BIT) {
    addComponentType(ParticleComponent::Runtime_ID, RequirementsFlag::REQUIRED);
    addComponentType(OnFireComponent::Runtime_ID, RequirementsFlag::OPTIONAL);

    // Calculate viewing perspective and matrices
    const auto pMatrix = mat4::perspective(1.5708F, 1.0F, 0.01F, 10.0F);
    const auto vMatrix = mat4::lookAt(
        vec3{ 256, 256, 256 }, vec3{ 256, 256, 0 }, vec3{ 0, 1, 0 });

    m_shader.uniformLocation(0, pMatrix);
    m_shader.uniformLocation(4, vMatrix);
}

//////////////////////////////////////////////////////////////////////
/// updateComponents
//////////////////////////////////////////////////////////////////////

void RenderSystem::updateComponents(
    const double& /*deltaTime*/,
    const std::vector<std::vector<ecsBaseComponent*>>& entityComponents) {
    // Update buffered data
    m_draw.setPrimitiveCount(static_cast<GLuint>(entityComponents.size()));
    m_dataBuffer.beginWriting();
    size_t offset(0ULL);
    for (const auto& components : entityComponents) {
        // Convert game particles into GPU renderable particles
        const auto& particle =
            *static_cast<ParticleComponent*>(components.front());
        const GPU_Particle data{
            particle.m_color, components.back() != nullptr ? 1 : 0,
            vec2(
                static_cast<float>(static_cast<int>(particle.m_pos.x())),
                static_cast<float>(static_cast<int>(particle.m_pos.y())))
        };
        m_dataBuffer.write(offset, sizeof(GPU_Particle), &data);
        offset += sizeof(GPU_Particle);
    }
    m_dataBuffer.endWriting();

    // Flush buffers and set starting parameters
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glDepthFunc(GL_LEQUAL);
    glBlendFunc(GL_ONE, GL_ZERO);

    m_shader.bind();
    m_model.bind();
    m_dataBuffer.bindBufferBase(GL_SHADER_STORAGE_BUFFER, 1);
    m_draw.drawCall(GL_QUADS);
    m_dataBuffer.endReading();
}