4jcraft/Minecraft.Client/Rendering/Polygon.cpp

#include "Rendering/Vertex.h"
#include "Polygon.h"
#include <algorithm>
#include <span>
#include <vector>

_Polygon::_Polygon(const std::span<const Vertex> vertices)
    : vertexCount(vertices.size()), vertices(vertices.begin(), vertices.end()) {}

_Polygon::_Polygon(const std::span<const Vertex, 4> vertices, int u0, int v0,
                   int u1, int v1, float xTexSize, float yTexSize)
    : vertexCount(vertices.size()) {
    // 4J - added - don't assume that u1 > u0, v1 > v0
    float us = (u1 > u0) ? (0.1f / xTexSize) : (-0.1f / xTexSize);
    float vs = (v1 > v0) ? (0.1f / yTexSize) : (-0.1f / yTexSize);

    this->vertices = {
        vertices[0].remap(u1 / xTexSize - us, v0 / yTexSize + vs),
        vertices[1].remap(u0 / xTexSize + us, v0 / yTexSize + vs),
        vertices[2].remap(u0 / xTexSize + us, v1 / yTexSize - vs),
        vertices[3].remap(u1 / xTexSize - us, v1 / yTexSize - vs),
    };
}

_Polygon::_Polygon(const std::span<const Vertex, 4> vertices, float u0,
                   float v0, float u1, float v1)
    : vertexCount(vertices.size()),
      vertices({
          vertices[0].remap(u1, v0),
          vertices[1].remap(u0, v0),
          vertices[2].remap(u0, v1),
          vertices[3].remap(u1, v1),
      }) {}

void _Polygon::mirror() {
    std::reverse(vertices.begin(), vertices.end());
}

void _Polygon::render(Tesselator* t, float scale) {
    Vec3 v0 = vertices[1].pos.vectorTo(vertices[0].pos);
    Vec3 v1 = vertices[1].pos.vectorTo(vertices[2].pos);
    Vec3 n = v1.cross(v0).normalize();

    t->begin();
    if (_flipNormal) {
        t->normal(-(float)n.x, -(float)n.y, -(float)n.z);
    } else {
        t->normal((float)n.x, (float)n.y, (float)n.z);
    }

    for (int i = 0; i < 4; i++) {
        Vertex v = vertices[i];
        t->vertexUV((float)(v.pos.x * scale), (float)(v.pos.y * scale),
                    (float)(v.pos.z * scale), (float)(v.u), (float)(v.v));
    }

    t->end();
}

_Polygon* _Polygon::flipNormal() {
    _flipNormal = true;
    return this;
}