3d-renderer/scripts/triangle.c

#include "triangle.h"

#include <stdio.h>
#include <math.h>

#include "display.h"

// TODO: Create implementation for triangle.h functions
int compare_vec2_t(const void* a, const void* b) {
    const int_vec2_t* arg1 = (const int_vec2_t*)a;
    const int_vec2_t* arg2 = (const int_vec2_t*)b;
    if (arg1->y < arg2->y) return -1;
    if (arg1->y > arg2->y) return 1;
    return 0;
}

#define FUNC (int)ceilf
#define FUNC2 (int)floorf

uint32_t invert_rgb(uint32_t color) {
    uint32_t a = color & 0xFF000000;          // Alpha channel
    uint32_t rgb = color & 0x00FFFFFF;        // RGB channels
    rgb = ~rgb & 0x00FFFFFF;                  // Invert RGB only
    return a | rgb;
}

///////////////////////////////////////////////////////////////////////////////
// Draw a filled a triangle with a flat bottom
///////////////////////////////////////////////////////////////////////////////
//
//        (x0,y0)
//          / \
//         /   \
//        /     \
//       /       \
//      /         \
//  (x1,y1)------(x2,y2)
//
///////////////////////////////////////////////////////////////////////////////
void fill_flat_bottom_triangle(int x0, int y0, int x1, int y1, int x2, int y2, uint32_t color) {
    // Find the two slopes (two triangle legs)
    float inv_slope_1 = (float)(x1 - x0) / (y1 - y0);
    float inv_slope_2 = (float)(x2 - x0) / (y2 - y0);

    // Start x_start and x_end from the top vertex (x0,y0)
    float x_start = x0;
    float x_end = x0;

    // Loop all the scanlines from top to bottom
    for (int y = y0; y <= y2; y++) {
        draw_line(x_start, y, x_end, y, color);
        x_start += inv_slope_1;
        x_end += inv_slope_2;
    }
}

///////////////////////////////////////////////////////////////////////////////
// Draw a filled a triangle with a flat top
///////////////////////////////////////////////////////////////////////////////
//
//  (x0,y0)------(x1,y1)
//      \         /
//       \       /
//        \     /
//         \   /
//          \ /
//        (x2,y2)
//
///////////////////////////////////////////////////////////////////////////////
void fill_flat_top_triangle(int x0, int y0, int x1, int y1, int x2, int y2, uint32_t color) {
    // Find the two slopes (two triangle legs)
    float inv_slope_1 = (float)(x2 - x0) / (y2 - y0);
    float inv_slope_2 = (float)(x2 - x1) / (y2 - y1);

    // Start x_start and x_end from the bottom vertex (x2,y2)
    float x_start = x2;
    float x_end = x2;

    // Loop all the scanlines from bottom to top
    for (int y = y2; y >= y0; y--) {
        draw_line(x_start, y, x_end, y, color);
        x_start -= inv_slope_1;
        x_end -= inv_slope_2;
    }
}

///////////////////////////////////////////////////////////////////////////////
// Draw a filled triangle with the flat-top/flat-bottom method
// We split the original triangle in two, half flat-bottom and half flat-top
///////////////////////////////////////////////////////////////////////////////
//
//          (x0,y0)
//            / \
//           /   \
//          /     \
//         /       \
//        /         \
//   (x1,y1)------(Mx,My)
//       \_           \
//          \_         \
//             \_       \
//                \_     \
//                   \    \
//                     \_  \
//                        \_\
//                           \
//                         (x2,y2)
//
///////////////////////////////////////////////////////////////////////////////
void draw_filled_triangle(int x0, int y0, int x1, int y1, int x2, int y2, uint32_t color) {
    // We need to sort the vertices by y-coordinate ascending (y0 < y1 < y2)
    if (y0 > y1) {
        int_swap(&y0, &y1);
        int_swap(&x0, &x1);
    }
    if (y1 > y2) {
        int_swap(&y1, &y2);
        int_swap(&x1, &x2);
    }
    if (y0 > y1) {
        int_swap(&y0, &y1);
        int_swap(&x0, &x1);
    }

    if (y1 == y2) {
        // Draw flat-bottom triangle
        fill_flat_bottom_triangle(x0, y0, x1, y1, x2, y2, color);
    } else if (y0 == y1) {
        // Draw flat-top triangle
        fill_flat_top_triangle(x0, y0, x1, y1, x2, y2, color);
    } else {
        // Calculate the new vertex (Mx,My) using triangle similarity
        int My = y1;
        int Mx = (((x2 - x0) * (y1 - y0)) / (y2 - y0)) + x0;

        // Draw flat-bottom triangle
        fill_flat_bottom_triangle(x0, y0, x1, y1, Mx, My, color);

        // Draw flat-top triangle
        fill_flat_top_triangle(x1, y1, Mx, My, x2, y2, color);
    }
}

void draw_textured_triangle(int x0, int y0, int x1, int y1, int x2, int y2, uint32_t* texture) {
    // sort by y
    int temp = 0, min_idx = 0, mid_idx = 1, max_idx = 2;

    // We need to sort the vertices by y-coordinate ascending (y0 < y1 < y2)
    if (y0 > y1) {
        int_swap(&y0, &y1);
        int_swap(&x0, &x1);
    }
    if (y1 > y2) {
        int_swap(&y1, &y2);
        int_swap(&x1, &x2);
    }
    if (y0 > y1) {
        int_swap(&y0, &y1);
        int_swap(&x0, &x1);
    }

    float inv_slope_1 = 0;
    float inv_slope_2 = 0;

    /*if (triangle.points[mid_idx].y - triangle.points[min_idx].y != 0) {
        inv_slope_1 = (float)(triangle.points[mid_idx].x - triangle.points[min_idx].x) / fabsf(triangle.points[mid_idx].y - triangle.points[min_idx].y);
    }

    if (triangle.points[max_idx].y - triangle.points[min_idx].y != 0) {
        inv_slope_2 = (float)(triangle.points[max_idx].x - triangle.points[min_idx].x) / fabsf(triangle.points[max_idx].y - triangle.points[min_idx].y);
    }

    for (int y = triangle.points[min_idx].y; y <= triangle.points[mid_idx].y; y++) {
        //float x_start = triangle
    }
    */


}