vertex.hpp

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#ifndef TOYMAKERENGINE_VERTEX_H
#define TOYMAKERENGINE_VERTEX_H
 
#include <SDL3/SDL_opengl.h>
 
#include <string>
#include <glm/glm.hpp>
#include <nlohmann/json.hpp>
 
namespace ToyMaker {

    enum DefaultAttributeLocation {
        LOCATION_POSITION=0, //< Location usually mapped to a vertex shader's "attrPosition" vec4 attribute.
        LOCATION_NORMAL=1, //< Location usually mapped to a vertex shader's "attrNormal" vec4 attribute.
        LOCATION_TANGENT=2, //< Location usually mapped to a vertex shader's "attrTangent" vec4 attribute.
        LOCATION_COLOR=3, //< Location usually mapped to a vertex shader's "attrColor" vec4 attribute.
        LOCATION_UV1=4, //< Location usually mapped to a vertex shader's "attrUV1" vec2 attribute.
        LOCATION_UV2=5, //< Location usually mapped to a vertex shader's "attrUV2" vec2 attribute.
        LOCATION_UV3=6, //< Location usually mapped to a vertex shader's "attrUV3" vec2 attribute.
    };

    struct VertexAttributeDescriptor {
        VertexAttributeDescriptor(const std::string& name, GLint layoutLocation, GLuint nComponents=1, GLenum type=GL_FLOAT)
        : 
            mName{name}, mLayoutLocation{layoutLocation}, mNComponents{nComponents}, 
            mType{type}, mSize { GetGLTypeSize(type) * nComponents}
        {
            assert(mNComponents >= 1 && mNComponents <= 4);
            assert(mType == GL_FLOAT || mType == GL_UNSIGNED_INT || mType == GL_INT);
        }

        std::string mName;

        GLint mLayoutLocation;

        GLuint mNComponents;

        GLenum mType;

        std::size_t mSize;

        bool operator==(const VertexAttributeDescriptor& other) const {
            if(
                other.mName == mName 
                && other.mLayoutLocation == mLayoutLocation 
                && other.mNComponents == mNComponents
                && other.mType == mType
                && other.mSize == mSize
            ) return true;
            return false;
        }
 
    private:
        static std::size_t GetGLTypeSize(GLenum type){
            std::size_t componentSize;
            switch(type) {
                case GL_FLOAT:
                    // fall through
                case GL_INT:
                    // fall through
                case GL_UNSIGNED_INT:
                    componentSize = sizeof(GLfloat);
                    break;
                default:
                    assert(false && "Unsupported or invalid attribute component type specified");
            }
            return componentSize;
        }
    };

    struct VertexLayout {
        VertexLayout(std::vector<VertexAttributeDescriptor> attributeList) : mAttributeList{attributeList} {}

        std::vector<VertexAttributeDescriptor> getAttributeList() const {
            return mAttributeList;
        }

        std::size_t computeStride() const {
            std::size_t stride {0};
            for(const auto& attribute : mAttributeList) {
                stride += attribute.mSize;
            }
            return stride;
        }

        std::size_t computeRelativeOffset(std::size_t attributeIndex) const {
            assert(attributeIndex < mAttributeList.size());
            std::size_t baseOffset {0};
            for(std::size_t i {0}; i < attributeIndex; ++i) {
                baseOffset += mAttributeList[i].mSize;
            }
            return baseOffset;
        }

        bool isSubsetOf(const VertexLayout& other) const {
            if(mAttributeList.size() > other.mAttributeList.size()) return false;
 
            std::size_t myAttributeIndex {0};
            for(std::size_t i{0}; i < other.mAttributeList.size() && myAttributeIndex < mAttributeList.size(); ++i) {
                if(other.mAttributeList[i] == mAttributeList[myAttributeIndex]){
                    ++myAttributeIndex;
                    if(myAttributeIndex == mAttributeList.size()) return true;
                }
            }
 
            return false;
        }
 
    private:
        std::vector<VertexAttributeDescriptor> mAttributeList {};
    };

    struct BuiltinVertexData {
        glm::vec4 mPosition;

        glm::vec4 mNormal;

        glm::vec4 mTangent;

        glm::vec4 mColor {1.f}; // by default, white

        glm::vec2 mUV1;

        glm::vec2 mUV2;

        glm::vec2 mUV3;
    };

    inline void from_json(const nlohmann::json& json, BuiltinVertexData& builtinVertexData) {
        json.at("position").at(0).get_to(builtinVertexData.mPosition.x);
        json.at("position").at(1).get_to(builtinVertexData.mPosition.y);
        json.at("position").at(2).get_to(builtinVertexData.mPosition.z);
        json.at("position").at(3).get_to(builtinVertexData.mPosition.w);
        json.at("normal").at(0).get_to(builtinVertexData.mNormal.x);
        json.at("normal").at(1).get_to(builtinVertexData.mNormal.y);
        json.at("normal").at(2).get_to(builtinVertexData.mNormal.z);
        json.at("normal").at(3).get_to(builtinVertexData.mNormal.w);
        json.at("tangent").at(0).get_to(builtinVertexData.mTangent.x);
        json.at("tangent").at(1).get_to(builtinVertexData.mTangent.y);
        json.at("tangent").at(2).get_to(builtinVertexData.mTangent.z);
        json.at("tangent").at(3).get_to(builtinVertexData.mTangent.w);
        json.at("color").at(0).get_to(builtinVertexData.mColor.r);
        json.at("color").at(1).get_to(builtinVertexData.mColor.g);
        json.at("color").at(2).get_to(builtinVertexData.mColor.b);
        json.at("color").at(3).get_to(builtinVertexData.mColor.a);
        json.at("uv1").at(0).get_to(builtinVertexData.mUV1.s);
        json.at("uv1").at(1).get_to(builtinVertexData.mUV1.t);
        json.at("uv2").at(0).get_to(builtinVertexData.mUV2.s);
        json.at("uv2").at(1).get_to(builtinVertexData.mUV2.t);
        json.at("uv3").at(0).get_to(builtinVertexData.mUV3.s);
        json.at("uv3").at(1).get_to(builtinVertexData.mUV3.t);
    }

    inline void to_json(nlohmann::json& json, const BuiltinVertexData& builtinVertexData) {
        json = {
            {"position", 
                { 
                    builtinVertexData.mPosition.x,
                    builtinVertexData.mPosition.y,
                    builtinVertexData.mPosition.z,
                    builtinVertexData.mPosition.w
                }
            },
            {"normal",
                {
                    builtinVertexData.mNormal.x,
                    builtinVertexData.mNormal.y,
                    builtinVertexData.mNormal.z,
                    builtinVertexData.mNormal.w,
                }
            },
            {"tangent",
                {
                    builtinVertexData.mTangent.x,
                    builtinVertexData.mTangent.y,
                    builtinVertexData.mTangent.z,
                    builtinVertexData.mTangent.w,
                }
            },
            {"color",
                {
                    builtinVertexData.mColor.r,
                    builtinVertexData.mColor.g,
                    builtinVertexData.mColor.b,
                    builtinVertexData.mColor.a,
                }
            },
            {"uv1",
                {
                    builtinVertexData.mUV1.s,
                    builtinVertexData.mUV1.t,
                }
            },
            {"uv2",
                {
                    builtinVertexData.mUV2.s,
                    builtinVertexData.mUV2.t,
                }
            },
            {"uv3",
                {
                    builtinVertexData.mUV3.s,
                    builtinVertexData.mUV3.t,
                }
            }
        };
    }

    inline VertexLayout BuiltinVertexLayout {
        {
            {"position", LOCATION_POSITION, 4, GL_FLOAT},
            {"normal", LOCATION_NORMAL, 4, GL_FLOAT},
            {"tangent", LOCATION_TANGENT, 4, GL_FLOAT},
            {"color", LOCATION_COLOR, 4, GL_FLOAT},
            {"UV1", LOCATION_UV1, 2, GL_FLOAT},
            {"UV2", LOCATION_UV2, 2, GL_FLOAT},
            {"UV3", LOCATION_UV3, 2, GL_FLOAT}
        }
    };
 
}
 
#endif