UwUGL/primatives/triangle.cpp

#pragma once

#include <stdint.h>
#include <algorithm>

#include "../datatypes.cpp"
#include "../helpers.cpp"
#include "../buffer.cpp"
#include "../shader.cpp"

namespace UwU {
  class Triangle {
    private:

    public:
      Triangle(uint16_t x0, uint16_t y0, uint16_t x1, uint16_t y1, uint16_t x2, uint16_t y2) {
        this->x0 = x0;
        this->y0 = y0;
        this->x1 = x1;
        this->y1 = y1;
        this->x2 = x2;
        this->y2 = y2;
      }
      Triangle() {}
      uint16_t x0;
      uint16_t y0;
      uint16_t x1;
      uint16_t y1;
      uint16_t x2;
      uint16_t y2;
      
      // Draw a triangle
      void draw (Buffer buffer, Shader shader) {
        uint16_t topX, topY, midX, midY, btmX, btmY;
        // Find top, middle and bottom points of triangle
        if (y0 <= y1 && y0 <= y2) {
          topX = x0;
          topY = y0;
          if (y1 < y2) {
            midX = x1;
            midY = y1;
            btmX = x2;
            btmY = y2;
          } else {
            midX = x2;
            midY = y2;
            btmX = x1;
            btmY = y1;
          }
        } else if (y1 <= y0 && y1 <= y2) {
          topX = x1;
          topY = y1;
          if (y0 < y2) {
            midX = x0;
            midY = y0;
            btmX = x2;
            btmY = y2;
          } else {
            midX = x2;
            midY = y2;
            btmX = x0;
            btmY = y0;
          }
        } else {
          topX = x2;
          topY = y2;
          if (y0 < y1) {
            midY = y0;
            midX = x0;
            btmX = x1;
            btmY = y1;
          } else {
            midX = x1;
            midY = y1;
            btmX = x0;
            btmY = y0;
          }
        }


        
        uint16_t height = 1 + btmY - topY;
        int16_t longBound[height];
        int16_t splitBound[height];

        // Calculate LUT for longest vertical line (from top to bottom)
        Helpers::bresenham(0, topX, height - 1, btmX, longBound);
        
        // Calculate LUT for short two lines
        Helpers::bresenham(0, topX, midY - topY, midX, splitBound);
        Helpers::bresenham(midY - topY, midX, height - 1, btmX, splitBound);

        if (shader.shaderType == COLOR) {
          // Left-handed triangle case (midpoint is left of triangle)
          if ((int16_t)midX < longBound[midY - topY]) {
            for (uint16_t i = 0; i < height; i++) {
              for (uint16_t x = (uint16_t)splitBound[i]; x <= (uint16_t)longBound[i]; x++) {
                buffer.drawPixel(x, i + (uint16_t)topY, shader.c0);
              }
            }
            // Right-handed triangle case (midpoint is right of triangle)
          } else {
            for (uint16_t i = 0; i < height; i++) {
              for (uint16_t x = (uint16_t)longBound[i]; x <= (uint16_t)splitBound[i]; x++) {
                buffer.drawPixel(x, i + (uint16_t)topY, shader.c0);
              }
            }
          }
          return;

        } else if (shader.shaderType == HGRADIENT) {
          // find left and right bounds
          uint16_t leftmost = std::min(x0, std::min(x1, x2));
          uint16_t rightmost = std::max(x0, std::max(x1, x2));

          // precompute gradient LUT
          Color cols[rightmost - leftmost];
          for (uint16_t x = leftmost; x < rightmost; x++) {
            cols[x - leftmost] = ShaderMethods::gradient(shader.u0, shader.scale, shader.c0, shader.c1, x);
          }

          // Left-handed triangle case (midpoint is left of triangle)
          if ((int16_t)midX < longBound[midY - topY]) {
            for (uint16_t i = 0; i < height; i++) {
              for (uint16_t x = (uint16_t)splitBound[i]; x <= (uint16_t)longBound[i]; x++) {
                buffer.drawPixel(x, i + (uint16_t)topY, cols[x - leftmost]);
              }
            }
            // Right-handed triangle case (midpoint is right of triangle)
          } else {
            for (uint16_t i = 0; i < height; i++) {
              for (uint16_t x = (uint16_t)longBound[i]; x <= (uint16_t)splitBound[i]; x++) {
                buffer.drawPixel(x, i + (uint16_t)topY, cols[x - leftmost]);
              }
            }
          }
          return;

        } else if (shader.shaderType == VGRADIENT) {
          Color c;

          // Left-handed triangle case (midpoint is left of triangle)
          if ((int16_t)midX < longBound[midY - topY]) {
            for (uint16_t i = 0; i < height; i++) {
              c = ShaderMethods::gradient(shader.v0, shader.scale, shader.c0, shader.c1, i + topY);
              for (uint16_t x = (uint16_t)splitBound[i]; x <= (uint16_t)longBound[i]; x++) {
                buffer.drawPixel(x, i + (uint16_t)topY, c);
              }
            }
            // Right-handed triangle case (midpoint is right of triangle)
          } else {
            for (uint16_t i = 0; i < height; i++) {
              c = ShaderMethods::gradient(shader.v0, shader.scale, shader.c0, shader.c1, i + topY);
              for (uint16_t x = (uint16_t)longBound[i]; x <= (uint16_t)splitBound[i]; x++) {
                buffer.drawPixel(x, i + (uint16_t)topY, c);
              }
            }
          }
          return;
        }
        return;
      }
    };
}