BillboardComponent.hpp

Go to the documentation of this file.

#pragma once
 
#include <iostream>
#include <string>
 
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
 
#include <AssetManager/Material.hpp>
#include <AssetManager/Mesh.hpp>
#include <Components/BaseComponent.hpp>
 
namespace shkyera {
 
template <RuntimeMode Mode = RuntimeMode::PRODUCTION>
struct BillboardComponent {
 public:
  enum class Orientation { CameraFacing, AxisAligned, WorldFixed };
 
  enum class Scale { World, Camera };
 
  enum class Occlusion { Occludable, NotOccludable };
 
  Orientation orientation{Orientation::CameraFacing};
  Scale scale{Scale::Camera};
  Occlusion occlusion{Occlusion::NotOccludable};
  HandleAndAsset<Material> material{};
 
  glm::mat4 getModelMatrix(const glm::mat4& baseMatrix, const glm::vec3& cameraPosition,
                           const glm::mat4& viewMatrix) const {
    glm::vec3 position = glm::vec3(baseMatrix[3]);
 
    glm::vec3 scaleVec(glm::length(glm::vec3(baseMatrix[0])), glm::length(glm::vec3(baseMatrix[1])),
                       glm::length(glm::vec3(baseMatrix[2])));
 
    if (scale == Scale::Camera) {
      float distance = glm::distance(cameraPosition, position);
      scaleVec *= distance / 30.0f;
    }
 
    glm::mat4 translation = glm::translate(glm::mat4(1.0f), position);
 
    glm::mat4 rotation(1.0f);
    if (orientation == Orientation::CameraFacing) {
      glm::mat3 camRot = glm::mat3(viewMatrix);
      camRot = glm::transpose(camRot);
      rotation = glm::mat4(camRot);
      rotation = glm::rotate(rotation, glm::radians(180.0f), glm::vec3(1, 0, 0));
    } else if (orientation == Orientation::AxisAligned) {
      glm::vec3 dir = cameraPosition - position;
      dir.y = 0.0f;  // ignore vertical component
      if (glm::length(dir) > 0.0001f) {
        dir = glm::normalize(dir);
      }
      float angle = std::atan2(dir.x, dir.z);
      rotation = glm::rotate(glm::mat4(1.0f), angle, glm::vec3(0, 1, 0));
    } else if (orientation == Orientation::WorldFixed) {
      glm::vec3 right = glm::normalize(glm::vec3(baseMatrix[0]));
      glm::vec3 up = glm::normalize(glm::vec3(baseMatrix[1]));
      glm::vec3 forward = glm::normalize(glm::vec3(baseMatrix[2]));
      glm::mat3 R_base;
      R_base[0] = right;
      R_base[1] = up;
      R_base[2] = forward;
      rotation = glm::mat4(R_base);
    }
 
    glm::mat4 correction = glm::rotate(glm::mat4(1.0f), glm::radians(90.0f), glm::vec3(1.0f, 0.0f, 0.0f));
 
    glm::mat4 scaling = glm::scale(glm::mat4(1.0f), scaleVec);
 
    glm::mat4 model = translation * rotation * correction * scaling;
    return model;
  }
};
 
}  // namespace shkyera