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#include <math.h>
#include <stdlib.h>
#include <stdio.h>
#define max(x, y) (((x) > (y)) ? (x) : (y))
#define min(x, y) (((x) < (y)) ? (x) : (y))
#define clip(_x, _min, _max) min(max(_x, _min), _max)
struct Tuple3D
{
float x;
float y;
float z;
};
void _render(const int *triangles,
const int ntri,
const float *light,
const float *directional,
const float *ambient,
const float *vertices,
const int nver,
unsigned char *image,
const int h, const int w)
{
int tri_p0_ind, tri_p1_ind, tri_p2_ind;
int color_index;
float dot00, dot01, dot11, dot02, dot12;
float cos_sum, det;
struct Tuple3D p0, p1, p2;
struct Tuple3D v0, v1, v2;
struct Tuple3D p, start, end;
struct Tuple3D ver_max = {-1.0e8, -1.0e8, -1.0e8};
struct Tuple3D ver_min = {1.0e8, 1.0e8, 1.0e8};
struct Tuple3D ver_mean = {0.0, 0.0, 0.0};
float *ver_normal = (float *)calloc(3 * nver, sizeof(float));
float *colors = (float *)malloc(3 * nver * sizeof(float));
float *depth_buffer = (float *)calloc(h * w, sizeof(float));
for (int i = 0; i < ntri; i++)
{
tri_p0_ind = triangles[3 * i];
tri_p1_ind = triangles[3 * i + 1];
tri_p2_ind = triangles[3 * i + 2];
// counter clockwise order
start.x = vertices[tri_p1_ind] - vertices[tri_p0_ind];
start.y = vertices[tri_p1_ind + 1] - vertices[tri_p0_ind + 1];
start.z = vertices[tri_p1_ind + 2] - vertices[tri_p0_ind + 2];
end.x = vertices[tri_p2_ind] - vertices[tri_p0_ind];
end.y = vertices[tri_p2_ind + 1] - vertices[tri_p0_ind + 1];
end.z = vertices[tri_p2_ind + 2] - vertices[tri_p0_ind + 2];
p.x = start.y * end.z - start.z * end.y;
p.y = start.z * end.x - start.x * end.z;
p.z = start.x * end.y - start.y * end.x;
ver_normal[tri_p0_ind] += p.x;
ver_normal[tri_p1_ind] += p.x;
ver_normal[tri_p2_ind] += p.x;
ver_normal[tri_p0_ind + 1] += p.y;
ver_normal[tri_p1_ind + 1] += p.y;
ver_normal[tri_p2_ind + 1] += p.y;
ver_normal[tri_p0_ind + 2] += p.z;
ver_normal[tri_p1_ind + 2] += p.z;
ver_normal[tri_p2_ind + 2] += p.z;
}
for (int i = 0; i < nver; ++i)
{
p.x = ver_normal[3 * i];
p.y = ver_normal[3 * i + 1];
p.z = ver_normal[3 * i + 2];
det = sqrt(p.x * p.x + p.y * p.y + p.z * p.z);
if (det <= 0)
det = 1e-6;
ver_normal[3 * i] /= det;
ver_normal[3 * i + 1] /= det;
ver_normal[3 * i + 2] /= det;
ver_mean.x += p.x;
ver_mean.y += p.y;
ver_mean.z += p.z;
ver_max.x = max(ver_max.x, p.x);
ver_max.y = max(ver_max.y, p.y);
ver_max.z = max(ver_max.z, p.z);
ver_min.x = min(ver_min.x, p.x);
ver_min.y = min(ver_min.y, p.y);
ver_min.z = min(ver_min.z, p.z);
}
ver_mean.x /= nver;
ver_mean.y /= nver;
ver_mean.z /= nver;
for (int i = 0; i < nver; ++i)
{
colors[3 * i] = vertices[3 * i];
colors[3 * i + 1] = vertices[3 * i + 1];
colors[3 * i + 2] = vertices[3 * i + 2];
colors[3 * i] -= ver_mean.x;
colors[3 * i] /= ver_max.x - ver_min.x;
colors[3 * i + 1] -= ver_mean.y;
colors[3 * i + 1] /= ver_max.y - ver_min.y;
colors[3 * i + 2] -= ver_mean.z;
colors[3 * i + 2] /= ver_max.z - ver_min.z;
p.x = light[0] - colors[3 * i];
p.y = light[1] - colors[3 * i + 1];
p.z = light[2] - colors[3 * i + 2];
det = sqrt(p.x * p.x + p.y * p.y + p.z * p.z);
if (det <= 0)
det = 1e-6;
colors[3 * i] = p.x / det;
colors[3 * i + 1] = p.y / det;
colors[3 * i + 2] = p.z / det;
colors[3 * i] *= ver_normal[3 * i];
colors[3 * i + 1] *= ver_normal[3 * i + 1];
colors[3 * i + 2] *= ver_normal[3 * i + 2];
cos_sum = colors[3 * i] + colors[3 * i + 1] + colors[3 * i + 2];
colors[3 * i] = clip(cos_sum * directional[0] + ambient[0], 0, 1);
colors[3 * i + 1] = clip(cos_sum * directional[1] + ambient[1], 0, 1);
colors[3 * i + 2] = clip(cos_sum * directional[2] + ambient[2], 0, 1);
}
for (int i = 0; i < ntri; ++i)
{
tri_p0_ind = triangles[3 * i];
tri_p1_ind = triangles[3 * i + 1];
tri_p2_ind = triangles[3 * i + 2];
p0.x = vertices[tri_p0_ind];
p0.y = vertices[tri_p0_ind + 1];
p0.z = vertices[tri_p0_ind + 2];
p1.x = vertices[tri_p1_ind];
p1.y = vertices[tri_p1_ind + 1];
p1.z = vertices[tri_p1_ind + 2];
p2.x = vertices[tri_p2_ind];
p2.y = vertices[tri_p2_ind + 1];
p2.z = vertices[tri_p2_ind + 2];
start.x = max(ceil(min(p0.x, min(p1.x, p2.x))), 0);
end.x = min(floor(max(p0.x, max(p1.x, p2.x))), w - 1);
start.y = max(ceil(min(p0.y, min(p1.y, p2.y))), 0);
end.y = min(floor(max(p0.y, max(p1.y, p2.y))), h - 1);
if (end.x < start.x || end.y < start.y)
continue;
v0.x = p2.x - p0.x;
v0.y = p2.y - p0.y;
v1.x = p1.x - p0.x;
v1.y = p1.y - p0.y;
// dot products np.dot(v0.T, v0)
dot00 = v0.x * v0.x + v0.y * v0.y;
dot01 = v0.x * v1.x + v0.y * v1.y;
dot11 = v1.x * v1.x + v1.y * v1.y;
// barycentric coordinates
start.z = dot00 * dot11 - dot01 * dot01;
if (start.z != 0)
start.z = 1 / start.z;
for (p.y = start.y; p.y <= end.y; p.y += 1.0)
{
for (p.x = start.x; p.x <= end.x; p.x += 1.0)
{
v2.x = p.x - p0.x;
v2.y = p.y - p0.y;
dot02 = v0.x * v2.x + v0.y * v2.y;
dot12 = v1.x * v2.x + v1.y * v2.y;
v2.z = (dot11 * dot02 - dot01 * dot12) * start.z;
v1.z = (dot00 * dot12 - dot01 * dot02) * start.z;
v0.z = 1 - v2.z - v1.z;
// judge is_point_in_tri by below line of code
if (v2.z > 0 && v1.z > 0 && v0.z > 0)
{
p.z = v0.z * p0.z + v1.z * p1.z + v2.z * p2.z;
color_index = p.y * w + p.x;
if (p.z > depth_buffer[color_index])
{
end.z = v0.z * colors[tri_p0_ind];
end.z += v1.z * colors[tri_p1_ind];
end.z += v2.z * colors[tri_p2_ind];
image[3 * color_index] = end.z * 255;
end.z = v0.z * colors[tri_p0_ind + 1];
end.z += v1.z * colors[tri_p1_ind + 1];
end.z += v2.z * colors[tri_p2_ind + 1];
image[3 * color_index + 1] = end.z * 255;
end.z = v0.z * colors[tri_p0_ind + 2];
end.z += v1.z * colors[tri_p1_ind + 2];
end.z += v2.z * colors[tri_p2_ind + 2];
image[3 * color_index + 2] = end.z * 255;
depth_buffer[color_index] = p.z;
}
}
}
}
}
free(depth_buffer);
free(colors);
free(ver_normal);
}
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