lines.h

/*****************************************************************************
 * VCLib                                                                     *
 * Visual Computing Library                                                  *
 *                                                                           *
 * Copyright(C) 2021-2026                                                    *
 * Visual Computing Lab                                                      *
 * ISTI - Italian National Research Council                                  *
 *                                                                           *
 * All rights reserved.                                                      *
 *                                                                           *
 * This program is free software; you can redistribute it and/or modify      *
 * it under the terms of the Mozilla Public License Version 2.0 as published *
 * by the Mozilla Foundation; either version 2 of the License, or            *
 * (at your option) any later version.                                       *
 *                                                                           *
 * This program 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              *
 * Mozilla Public License Version 2.0                                        *
 * (https://www.mozilla.org/en-US/MPL/2.0/) for more details.                *
 ****************************************************************************/
 
#ifndef VCL_BGFX_PRIMITIVES_LINES_H
#define VCL_BGFX_PRIMITIVES_LINES_H
 
#include <vclib/bgfx/primitives/lines/cpu_generated_lines.h>
#include <vclib/bgfx/primitives/lines/primitive_lines.h>
#include <vclib/bgfx/uniform.h>
 
#include <vclib/base.h>
#include <vclib/space/core.h>
 
#include <variant>
 
#include <bgfx/bgfx.h>
 
namespace vcl {
 
// TODO: add shading per-line (flat, per-line normal) (?)
class Lines
{
public:
    enum class ColorToUse {
        PER_VERTEX, // Select color form vertex color
        PER_EDGE,   // Select color from edge buffer color
        GENERAL     // Use general color in uniform data
    };
 
    enum class ImplementationType {
        PRIMITIVE     = 0, // Use bgfx primitive lines (not implemented)
        CPU_GENERATED = 1, // Buffers pre-generated in CPU
 
        // TODO: uncomment when they will be implemented
        // GPU_GENERATED,     // Buffers pre-generated in GPU with computes
        // CPU_INSTANCING,    // Using Instancing with buffers generated in CPU
        // GPU_INSTANCING,    // Using Instancing with buffer generated in GPU
        //                    // computes
        // TEXTURE_INSTANCING, // Using Instancing with textures generated in
        // GPU computes
 
        COUNT
    };
 
private:
    float mThickness = 5.0f;
 
    // TODO: shading should become a enum with options: PER_VERTEX, PER_EDGE,
    // NONE
    // PER_EDGE means that we use a buffer of normals for each edge
    bool mShadingPerVertexCapability = false; // true if normals provided
    bool mShadingPerVertex           = false;
 
    BitSet8    mColorCapability = {false, false, true}; // general color only
    ColorToUse mColorToUse      = ColorToUse::GENERAL;
    Color      mGeneralColor    = Color::ColorABGR::LightGray;
 
    ImplementationType mType = ImplementationType::COUNT;
 
    std::variant<detail::PrimitiveLines, detail::CPUGeneratedLines>
        mLinesImplementation;
 
    static inline Uniform sSettingUH;
 
public:
    Lines(ImplementationType type = ImplementationType::COUNT)
    {
        if (type == ImplementationType::COUNT)
            type = defaultImplementationType(false);
        setImplementationType(type);
    };
 
    Lines(
        const std::vector<float>& vertCoords,
        const std::vector<float>& vertNormals,
        const std::vector<uint>&  vertColors,
        const std::vector<uint>&  lineColors,
        float                     thickness        = 5.0f,
        bool                      shadingPerVertex = false,
        ColorToUse                colorToUse       = ColorToUse::GENERAL,
        ImplementationType        type = ImplementationType::COUNT) :
            mThickness(thickness)
    {
        setPoints(vertCoords, vertNormals, vertColors, lineColors, type);
        setShading(shadingPerVertex);
        setColorToUse(colorToUse);
    }
 
    Lines(
        const std::vector<float>& vertCoords,
        const std::vector<uint>&  lineIndices,
        const std::vector<float>& vertNormals,
        const std::vector<uint>&  vertColors,
        const std::vector<uint>&  lineColors,
        float                     thickness        = 5.0f,
        bool                      shadingPerVertex = false,
        ColorToUse                colorToUse       = ColorToUse::GENERAL,
        ImplementationType        type = ImplementationType::COUNT) :
            mThickness(thickness)
    {
        setPoints(
            vertCoords, lineIndices, vertNormals, vertColors, lineColors, type);
        setShading(shadingPerVertex);
        setColorToUse(colorToUse);
    }
 
    void setPoints(
        const std::vector<float>& vertCoords,
        const std::vector<float>& vertNormals,
        const std::vector<uint>&  vertColors,
        const std::vector<uint>&  lineColors,
        ImplementationType        type = ImplementationType::COUNT)
    {
        using enum ImplementationType;
        using namespace detail;
 
        if (type == COUNT)
            type = defaultImplementationType(true);
        setImplementationType(type);
 
        switch (mType) {
        case PRIMITIVE: // always supported
            std::get<PrimitiveLines>(mLinesImplementation)
                .setPoints(vertCoords, vertNormals, vertColors, lineColors);
            break;
 
        case CPU_GENERATED: // always supported
            std::get<CPUGeneratedLines>(mLinesImplementation)
                .setPoints(vertCoords, vertNormals, vertColors, lineColors);
            break;
        default: break;
        }
        updateShadingCapability(vertNormals);
        updateColorCapability(vertColors, lineColors);
    }
 
    void setPoints(
        const std::vector<float>& vertCoords,
        const std::vector<uint>&  lineIndices,
        const std::vector<float>& vertNormals,
        const std::vector<uint>&  vertColors,
        const std::vector<uint>&  lineColors,
        ImplementationType        type = ImplementationType::COUNT)
    {
        using enum ImplementationType;
        using namespace detail;
 
        if (type == COUNT)
            type = defaultImplementationType(true);
        setImplementationType(type);
 
        switch (mType) {
        case PRIMITIVE: // always supported
            std::get<PrimitiveLines>(mLinesImplementation)
                .setPoints(
                    vertCoords,
                    lineIndices,
                    vertNormals,
                    vertColors,
                    lineColors);
            break;
 
        case CPU_GENERATED: // always supported
            std::get<CPUGeneratedLines>(mLinesImplementation)
                .setPoints(
                    vertCoords,
                    lineIndices,
                    vertNormals,
                    vertColors,
                    lineColors);
            break;
        default: break;
        }
        updateShadingCapability(vertNormals);
        updateColorCapability(vertColors, lineColors);
    }
 
    float thickness() const { return mThickness; }
 
    float& thickness() { return mThickness; }
 
    bool shadingPerVertex() const { return mShadingPerVertex; }
 
    ColorToUse colorToUse() const { return mColorToUse; }
 
    Color generalColor() const { return mGeneralColor; }
 
    Color& generalColor() { return mGeneralColor; }
 
    ImplementationType implementationType() const { return mType; }
 
    void setShading(bool perVertex)
    {
        if (!mShadingPerVertexCapability && perVertex) {
            throw std::runtime_error(
                "Lines::setShading(): shading per vertex not supported by the "
                "current buffers.");
        }
        else {
            mShadingPerVertex = perVertex;
        }
    }
 
    void setColorToUse(ColorToUse color)
    {
        if (!mColorCapability[toUnderlying(color)]) {
            throw std::runtime_error(
                "Lines::setColorToUse(): color option not supported by the "
                "current buffers.");
        }
        else {
            mColorToUse = color;
        }
    }
 
    void draw(uint viewId) const
    {
        using enum ImplementationType;
        using namespace detail;
 
        bindSettingsUniform();
        if (mType == PRIMITIVE)
            std::get<PrimitiveLines>(mLinesImplementation).draw(viewId);
 
        if (mType == CPU_GENERATED)
            std::get<CPUGeneratedLines>(mLinesImplementation).draw(viewId);
    }
 
private:
    ImplementationType defaultImplementationType(
        bool cpuMemPointsProvided) const
    {
        using enum ImplementationType;
 
        if (cpuMemPointsProvided)
            return CPU_GENERATED;
        else
            return PRIMITIVE;
    }
 
    bool setImplementationType(ImplementationType type)
    {
        using enum ImplementationType;
 
        if (mType == type)
            return false; // no change
 
        // TODO: check whether caps allow the new implementation type
        // then set the implementation and the type
        switch (type) {
        case PRIMITIVE: // always supported
            mLinesImplementation = detail::PrimitiveLines();
            mType                = type;
            return true;
 
        case CPU_GENERATED: // always supported
            mLinesImplementation = detail::CPUGeneratedLines();
            mType                = type;
            return true;
 
        default: return false; // not supported
        }
    }
 
    void updateShadingCapability(const std::vector<float>& vertNormals)
    {
        mShadingPerVertexCapability = !vertNormals.empty();
        if (!mShadingPerVertexCapability)
            mShadingPerVertex = false;
    }
 
    void updateColorCapability(
        const std::vector<uint>& vertColors,
        const std::vector<uint>& lineColors)
    {
        using enum ColorToUse;
 
        mColorCapability[toUnderlying(PER_VERTEX)] = !vertColors.empty();
        mColorCapability[toUnderlying(PER_EDGE)]   = !lineColors.empty();
 
        if (!mColorCapability[toUnderlying(mColorToUse)])
            mColorToUse = GENERAL;
    }
 
    void bindSettingsUniform() const
    {
        // lazy initialization
        // to avoid creating uniforms before bgfx is initialized
        if (!sSettingUH.isValid())
            sSettingUH = Uniform("u_settings", bgfx::UniformType::Vec4);
 
        float data[] = {
            mThickness,
            static_cast<float>(mColorToUse),
            std::bit_cast<float>(mGeneralColor.abgr()),
            static_cast<float>(mShadingPerVertex)};
        sSettingUH.bind(data);
    }
};
 
} // namespace vcl
 
#endif // VCL_BGFX_PRIMITIVES_LINES_H