mesh.h

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// SPDX-License-Identifier: Apache-2.0
// Copyright 2025-2026 Arnis Lektauers
//
// Created by Arnis Lektauers on 08.11.2025.
//
#pragma once
 
#include <cstddef>
 
#include <core/shape/boundingBox.h>
#include <core/refCountedObject.h>
#include <platform/graphics/indexBuffer.h>
#include <platform/graphics/vertexBuffer.h>
 
namespace visutwin::canvas
{
    enum PrimitiveType
    {
        PRIMITIVE_POINTS = 0,
        PRIMITIVE_LINES = 1,
        PRIMITIVE_LINELOOP = 2,
        PRIMITIVE_LINESTRIP = 3,
        PRIMITIVE_TRIANGLES = 4,
        PRIMITIVE_TRISTRIP = 5,
        PRIMITIVE_TRIFAN = 6
    };

    struct Primitive
    {
        PrimitiveType type = PrimitiveType::PRIMITIVE_TRIANGLES;

        int base = 0;

        int baseVertex = 0;

        int count = 0;

        bool indexed = false;
    };

    struct GeometryData
    {
        // Maximum number of vertices that can be stored without reallocation
        int maxVertices = 0;
 
        // Maximum number of indices that can be stored without reallocation
        int maxIndices = 0;
 
        // Current number of vertices in use
        int vertexCount = 0;
 
        // Current number of indices in use
        int indexCount = 0;
    };

    class Mesh : public RefCountedObject
    {
    public:
        int aabbVer() const { return _aabbVer; }
 
        const BoundingBox& aabb() const { return _aabb; }
 
        void setAabb(const BoundingBox& bounds)
        {
            _aabb = bounds;
            _aabbVer++;
        }
 
        void setVertexBuffer(const std::shared_ptr<VertexBuffer>& vb)
        {
            _vertexBuffer = vb;
            _aabbVer++;
        }
 
        void setIndexBuffer(const std::shared_ptr<IndexBuffer>& ib, const size_t style = 0)
        {
            if (_indexBuffer.size() <= style) {
                _indexBuffer.resize(style + 1);
            }
            _indexBuffer[style] = ib;
            _aabbVer++;
        }
 
        void setPrimitive(const Primitive& p, const size_t style = 0)
        {
            if (_primitive.size() <= style) {
                _primitive.resize(style + 1);
            }
            _primitive[style] = p;
            _aabbVer++;
        }
 
        std::shared_ptr<VertexBuffer> getVertexBuffer() const { return _vertexBuffer; }
 
        std::shared_ptr<IndexBuffer> getIndexBuffer(const size_t style = 0) const
        {
            return style < _indexBuffer.size() ? _indexBuffer[style] : nullptr;
        }
 
        Primitive getPrimitive(const size_t style = 0) const
        {
            return style < _primitive.size() ? _primitive[style] : Primitive{};
        }
 
    private:
        void initGeometryData();
 
        // Internal AABB version counter
        int _aabbVer = 0;
 
        // AABB representing object space bounds
        BoundingBox _aabb;
 
        // Geometry data for programmatic mesh modification
        std::unique_ptr<GeometryData> _geometryData;
 
        // Array of index buffers for different render styles
        std::vector<std::shared_ptr<IndexBuffer>> _indexBuffer;
 
        // The vertex buffer holding vertex data
        std::shared_ptr<VertexBuffer> _vertexBuffer;
 
        // Array of primitive objects defining how to interpret vertex/index data
        std::vector<Primitive> _primitive;
    };
}