model3d.c

#include "vc.c"

#define WIDTH 960
#define HEIGHT 720
#define BACKGROUND_COLOR 0xFF181818

#define PI 3.14159265359

float sqrtf(float x);
float atan2f(float y, float x);
float sinf(float x);
float cosf(float x);

static uint32_t pixels[WIDTH*HEIGHT];
static float zbuffer[WIDTH*HEIGHT] = {0};
static float angle = 0;

typedef struct {
    float x, y;
} Vector2;

static Vector2 make_vector2(float x, float y)
{
    Vector2 v2;
    v2.x = x;
    v2.y = y;
    return v2;
}

typedef struct {
    float x, y, z;
} Vector3;

static Vector3 make_vector3(float x, float y, float z)
{
    Vector3 v3;
    v3.x = x;
    v3.y = y;
    v3.z = z;
    return v3;
}

#define EPSILON 1e-6

static Vector2 project_3d_2d(Vector3 v3)
{
    if (v3.z < 0) v3.z = -v3.z;
    if (v3.z < EPSILON) v3.z += EPSILON;
    return make_vector2(v3.x/v3.z, v3.y/v3.z);
}

static Vector2 project_2d_scr(Vector2 v2)
{
    return make_vector2((v2.x + 1)/2*WIDTH, (1 - (v2.y + 1)/2)*HEIGHT);
}

static Vector3 rotate_y(Vector3 p, float delta_angle)
{
    float angle = atan2f(p.z, p.x) + delta_angle;
    float mag = sqrtf(p.x*p.x + p.z*p.z);
    return make_vector3(cosf(angle)*mag, p.y, sinf(angle)*mag);
}

typedef enum {
    FACE_V1,
    FACE_V2,
    FACE_V3,
    FACE_VT1,
    FACE_VT2,
    FACE_VT3,
    FACE_VN1,
    FACE_VN2,
    FACE_VN3,
} Face_Index;

float vector3_dot(Vector3 a, Vector3 b)
{
    return a.x*b.x + a.y*b.y + a.z*b.z;
}

Olivec_Canvas vc_render(float dt)
{
    angle += 0.25*PI*dt;

    Olivec_Canvas oc = olivec_canvas(pixels, WIDTH, HEIGHT, WIDTH);
    olivec_fill(oc, BACKGROUND_COLOR);
    for (size_t i = 0; i < WIDTH*HEIGHT; ++i) zbuffer[i] = 0;

    Vector3 camera = {0, 0, 1};
    for (size_t i = 0; i < faces_count; ++i) {
        int a, b, c;

        a = faces[i][FACE_V1];
        b = faces[i][FACE_V2];
        c = faces[i][FACE_V3];
        Vector3 v1 = rotate_y(make_vector3(vertices[a][0], vertices[a][1], vertices[a][2]), angle);
        Vector3 v2 = rotate_y(make_vector3(vertices[b][0], vertices[b][1], vertices[b][2]), angle);
        Vector3 v3 = rotate_y(make_vector3(vertices[c][0], vertices[c][1], vertices[c][2]), angle);
        v1.z += 1.5; v2.z += 1.5; v3.z += 1.5;

        a = faces[i][FACE_VN1];
        b = faces[i][FACE_VN2];
        c = faces[i][FACE_VN3];
        Vector3 vn1 = rotate_y(make_vector3(normals[a][0], normals[a][1], normals[a][2]), angle);
        Vector3 vn2 = rotate_y(make_vector3(normals[b][0], normals[b][1], normals[b][2]), angle);
        Vector3 vn3 = rotate_y(make_vector3(normals[c][0], normals[c][1], normals[c][2]), angle);
        if (vector3_dot(camera, vn1) > 0.0 &&
            vector3_dot(camera, vn2) > 0.0 &&
            vector3_dot(camera, vn3) > 0.0) continue;


        Vector2 p1 = project_2d_scr(project_3d_2d(v1));
        Vector2 p2 = project_2d_scr(project_3d_2d(v2));
        Vector2 p3 = project_2d_scr(project_3d_2d(v3));

        int x1 = p1.x;
        int x2 = p2.x;
        int x3 = p3.x;
        int y1 = p1.y;
        int y2 = p2.y;
        int y3 = p3.y;
        int lx, hx, ly, hy;
        if (olivec_normalize_triangle(oc.width, oc.height, x1, y1, x2, y2, x3, y3, &lx, &hx, &ly, &hy)) {
            for (int y = ly; y <= hy; ++y) {
                for (int x = lx; x <= hx; ++x) {
                    int u1, u2, det;
                    if (olivec_barycentric(x1, y1, x2, y2, x3, y3, x, y, &u1, &u2, &det)) {
                        int u3 = det - u1 - u2;
                        float z = 1/v1.z*u1/det + 1/v2.z*u2/det + 1/v3.z*u3/det;
                        float near = 0.1f;
                        float far = 5.0f;
                        if (1.0f/far < z && z < 1.0f/near && z > zbuffer[y*WIDTH + x]) {
                            zbuffer[y*WIDTH + x] = z;
                            OLIVEC_PIXEL(oc, x, y) = mix_colors3(0xFF1818FF, 0xFF18FF18, 0xFFFF1818, u1, u2, det);

                            z = 1.0f/z;
                            if (z >= 1.0) {
                                z -= 1.0;
                                uint32_t v = z*255;
                                if (v > 255) v = 255;
                                olivec_blend_color(&OLIVEC_PIXEL(oc, x, y), (v<<(3*8)));
                            }
                        }
                    }
                }
            }
        }
    }

    return oc;
}