path: root/src/maths/primitives.c

#include "primitives.h"
#include "colours.h"
#include "log.h"
#include "maths.h"
#include "maths_types.h"
#include "ral_types.h"
#include "render_types.h"

// --- Helpers

void push_triangle(u32_darray* arr, u32 i0, u32 i1, u32 i2) {
  u32_darray_push(arr, i0);
  u32_darray_push(arr, i1);
  u32_darray_push(arr, i2);
}

Vec3 plane_vertex_positions[] = {
  (Vec3){ -0.5, 0, -0.5 },
  (Vec3){ 0.5, 0, -0.5 },
  (Vec3){ -0.5, 0, 0.5 },
  (Vec3){ 0.5, 0, 0.5 },
};

Geometry Geo_CreatePlane(f32x2 extents, u32 tiling_u, u32 tiling_v) {
  CASSERT(tiling_u >= 1 && tiling_v >= 1);
  Vertex_darray* vertices = Vertex_darray_new(4);
  u32_darray* indices = u32_darray_new(vertices->len);

  Vec3 vert_pos[4];
  memcpy(&vert_pos, plane_vertex_positions, sizeof(plane_vertex_positions));
  for (int i = 0; i < 4; i++) {
    vert_pos[i].x *= extents.x;
    vert_pos[i].z *= extents.y;
  }
  VERT_3D(vertices, vert_pos[0], VEC3_Y, vec2(0, 0));                        // back left
  VERT_3D(vertices, vert_pos[1], VEC3_Y, vec2(1 * tiling_u, 0 * tiling_v));  // back right
  VERT_3D(vertices, vert_pos[2], VEC3_Y, vec2(0, 1 * tiling_v));             // front left
  VERT_3D(vertices, vert_pos[3], VEC3_Y, vec2(1 * tiling_u, 1 * tiling_v));  // front right

  // push_triangle(indices, 0, 1, 2);
  // push_triangle(indices, 2, 1, 3);
  push_triangle(indices, 2, 1, 0);
  push_triangle(indices, 1, 2, 3);

  for (int i = 0; i < 4; i++) {
    printf("Vertex %d: (%f, %f, %f)\n", i, vert_pos[i].x, vert_pos[i].y, vert_pos[i].z);
  }

  Geometry geo = { .format = VERTEX_STATIC_3D,
                   .vertices = vertices,
                   .has_indices = true,
                   .index_count = indices->len,
                   .indices = indices };

  return geo;
}

Geometry Geo_CreateCuboid(f32x3 extents) {
  Vertex_darray* vertices = Vertex_darray_new(36);

  // back faces
  VERT_3D(vertices, BACK_TOP_RIGHT, VEC3_NEG_Z, vec2(1, 0));
  VERT_3D(vertices, BACK_BOT_LEFT, VEC3_NEG_Z, vec2(0, 1));
  VERT_3D(vertices, BACK_TOP_LEFT, VEC3_NEG_Z, vec2(0, 0));
  VERT_3D(vertices, BACK_TOP_RIGHT, VEC3_NEG_Z, vec2(1, 0));
  VERT_3D(vertices, BACK_BOT_RIGHT, VEC3_NEG_Z, vec2(1, 1));
  VERT_3D(vertices, BACK_BOT_LEFT, VEC3_NEG_Z, vec2(0, 1));

  // front faces
  VERT_3D(vertices, FRONT_BOT_LEFT, VEC3_Z, vec2(0, 1));
  VERT_3D(vertices, FRONT_TOP_RIGHT, VEC3_Z, vec2(1, 0));
  VERT_3D(vertices, FRONT_TOP_LEFT, VEC3_Z, vec2(0, 0));
  VERT_3D(vertices, FRONT_BOT_LEFT, VEC3_Z, vec2(0, 1));
  VERT_3D(vertices, FRONT_BOT_RIGHT, VEC3_Z, vec2(1, 1));
  VERT_3D(vertices, FRONT_TOP_RIGHT, VEC3_Z, vec2(1, 0));

  // top faces
  VERT_3D(vertices, BACK_TOP_LEFT, VEC3_Y, vec2(0, 0));
  VERT_3D(vertices, FRONT_TOP_LEFT, VEC3_Y, vec2(0, 1));
  VERT_3D(vertices, FRONT_TOP_RIGHT, VEC3_Y, vec2(1, 1));
  VERT_3D(vertices, BACK_TOP_LEFT, VEC3_Y, vec2(0, 0));
  VERT_3D(vertices, FRONT_TOP_RIGHT, VEC3_Y, vec2(1, 1));
  VERT_3D(vertices, BACK_TOP_RIGHT, VEC3_Y, vec2(1, 0));

  // bottom faces
  VERT_3D(vertices, BACK_BOT_LEFT, VEC3_NEG_Y, vec2(0, 1));
  VERT_3D(vertices, FRONT_BOT_RIGHT, VEC3_NEG_Y, vec2(1, 1));
  VERT_3D(vertices, FRONT_BOT_LEFT, VEC3_NEG_Y, vec2(0, 1));
  VERT_3D(vertices, BACK_BOT_LEFT, VEC3_NEG_Y, vec2(0, 1));
  VERT_3D(vertices, BACK_BOT_RIGHT, VEC3_NEG_Y, vec2(1, 1));
  VERT_3D(vertices, FRONT_BOT_RIGHT, VEC3_NEG_Y, vec2(0, 1));

  // right faces
  VERT_3D(vertices, FRONT_TOP_RIGHT, VEC3_X, vec2(0, 0));
  VERT_3D(vertices, BACK_BOT_RIGHT, VEC3_X, vec2(1, 1));
  VERT_3D(vertices, BACK_TOP_RIGHT, VEC3_X, vec2(1, 0));
  VERT_3D(vertices, BACK_BOT_RIGHT, VEC3_X, vec2(1, 1));
  VERT_3D(vertices, FRONT_TOP_RIGHT, VEC3_X, vec2(0, 0));
  VERT_3D(vertices, FRONT_BOT_RIGHT, VEC3_X, vec2(0, 1));

  // left faces
  VERT_3D(vertices, FRONT_TOP_LEFT, VEC3_NEG_X, vec2(0, 0));
  VERT_3D(vertices, BACK_TOP_LEFT, VEC3_NEG_X, vec2(0, 0));
  VERT_3D(vertices, BACK_BOT_LEFT, VEC3_NEG_X, vec2(0, 0));
  VERT_3D(vertices, BACK_BOT_LEFT, VEC3_NEG_X, vec2(0, 0));
  VERT_3D(vertices, FRONT_BOT_LEFT, VEC3_NEG_X, vec2(0, 0));
  VERT_3D(vertices, FRONT_TOP_LEFT, VEC3_NEG_X, vec2(0, 0));

  u32_darray* indices = u32_darray_new(vertices->len);

  for (u32 i = 0; i < vertices->len; i++) {
    u32_darray_push(indices, i);
    vertices->data[i].static_3d.position =
        vec3_sub(vertices->data[i].static_3d.position,
                 vec3(0.5, 0.5, 0.5));  // make center of the cube is the origin of mesh space
  }

  Geometry geo = {
    .format = VERTEX_STATIC_3D,
    .vertices = vertices,
    .has_indices = true,
    .index_count = indices->len,
    .indices = indices,  // FIXME: make darray methods that return stack allocated struct
  };

  return geo;
}

// --- Spheres

Vec3 spherical_to_cartesian_coords(f32 rho, f32 theta, f32 phi) {
  f32 x = rho * sin(phi) * cos(theta);
  f32 y = rho * cos(phi);
  f32 z = rho * sin(phi) * sin(theta);
  return vec3(x, y, z);
}

Geometry Geo_CreateUVsphere(f32 radius, u32 north_south_lines, u32 east_west_lines) {
  assert(east_west_lines >= 3);  // sphere will be degenerate and look gacked without at least 3
  assert(north_south_lines >= 3);

  Vertex_darray* vertices = Vertex_darray_new(2 + (east_west_lines - 1) * north_south_lines);

  // Create a UV sphere with spherical coordinates
  // a point P on the unit sphere can be represented P(r, theta, phi)
  // for each vertex we must convert that to a cartesian R3 coordinate

  // Top point
  Vertex top = { .static_3d = { .position = vec3(0, radius, 0),
                                .normal = vec3_normalise(vec3(0, radius, 0)),
                                .tex_coords = vec2(0, 0) } };
  Vertex_darray_push(vertices, top);

  // parallels
  for (u32 i = 0; i < (east_west_lines - 1); i++) {
    // phi should range from 0 to pi
    f32 phi = PI * (((f32)i + 1) / (f32)east_west_lines);

    // meridians
    for (u32 j = 0; j < east_west_lines; j++) {
      // theta should range from 0 to 2PI
      f32 theta = TAU * ((f32)j / (f32)north_south_lines);
      Vec3 position = spherical_to_cartesian_coords(radius, theta, phi);
      // f32 d = vec3_len(position);
      // print_vec3(position);
      // printf("Phi %f Theta %f d %d\n", phi, theta, d);
      // assert(d == radius);  // all points on the sphere should be 'radius' away from the origin
      Vertex v = { .static_3d = {
                       .position = position,
                       .normal =
                           vec3_normalise(position),  // normal vector on sphere is same as position
                       .tex_coords = vec2(0, 0)       // TODO
                   } };
      Vertex_darray_push(vertices, v);
    }
  }

  // Bottom point
  Vertex bot = { .static_3d = { .position = vec3(0, -radius, 0),
                                .normal = vec3_normalise(vec3(0, -radius, 0)),
                                .tex_coords = vec2(0, 0) } };
  Vertex_darray_push(vertices, bot);

  u32_darray* indices = u32_darray_new(1);

  // top bottom rings
  for (u32 i = 0; i < north_south_lines; i++) {
    u32 i1 = i + 1;
    u32 i2 = (i + 1) % north_south_lines + 1;
    push_triangle(indices, 0, i2, i1);
    /* TRACE("Push triangle (%.2f %.2f %.2f)->(%.2f %.2f %.2f)->(%.2f %.2f %.2f)\n", */
    /*       vertices->data[0].static_3d.position.x, vertices->data[0].static_3d.position.y, */
    /*       vertices->data[0].static_3d.position.z, vertices->data[i1].static_3d.position.x, */
    /*       vertices->data[i1].static_3d.position.y, vertices->data[i1].static_3d.position.z, */
    /*       vertices->data[i2].static_3d.position.x, vertices->data[i2].static_3d.position.y, */
    /*       vertices->data[i2].static_3d.position.z); */
    u32 bot = vertices->len - 1;
    u32 i3 = i + north_south_lines * (east_west_lines - 2) + 1;
    u32 i4 = (i + 1) % north_south_lines + north_south_lines * (east_west_lines - 2) + 1;
    push_triangle(indices, bot, i3, i4);
  }

  // quads
  for (u32 i = 0; i < east_west_lines - 2; i++) {
    u32 ring_start = i * north_south_lines + 1;
    u32 next_ring_start = (i + 1) * north_south_lines + 1;
    /* printf("ring start %d next ring start %d\n", ring_start, next_ring_start); */
    /* print_vec3(vertices->data[ring_start].static_3d.position); */
    /* print_vec3(vertices->data[next_ring_start].static_3d.position); */
    for (u32 j = 0; j < north_south_lines; j++) {
      u32 i0 = ring_start + j;
      u32 i1 = next_ring_start + j;
      u32 i2 = ring_start + (j + 1) % north_south_lines;
      u32 i3 = next_ring_start + (j + 1) % north_south_lines;
      push_triangle(indices, i0, i2, i1);
      /* TRACE("Push triangle (%.2f %.2f %.2f)->(%.2f %.2f %.2f)->(%.2f %.2f %.2f)\n", */
      /*       vertices->data[i0].static_3d.position.x, vertices->data[i0].static_3d.position.y, */
      /*       vertices->data[i0].static_3d.position.z, vertices->data[i1].static_3d.position.x, */
      /*       vertices->data[i1].static_3d.position.y, vertices->data[i1].static_3d.position.z, */
      /*       vertices->data[i2].static_3d.position.x, vertices->data[i2].static_3d.position.y, */
      /*       vertices->data[i2].static_3d.position.z); */
      push_triangle(indices, i1, i2, i3);
    }
  }

  Geometry geo = {
    .format = VERTEX_STATIC_3D,
    .vertices = vertices,
    .has_indices = true,
    .index_count = indices->len,
    .indices = indices,
  };

  return geo;
}

Geometry Geo_CreateCone(f32 radius, f32 height, u32 resolution) {
  Vertex_darray* vertices = Vertex_darray_new((resolution + 1) * 2);
  u32_darray* indices = u32_darray_new(resolution * 2 * 3);

  // TODO: decide how UVs are unwrapped

  // tip
  VERT_3D(vertices, vec3(0.0, height, 0.0), VEC3_Y, vec2(0, 0));

  // sides
  f32 step = TAU / resolution;

  for (u32 i = 0; i < resolution; i++) {
    f32 x = cos(step * i) * radius;
    f32 z = sin(step * i) * radius;
    Vec3 pos = vec3(x, 0.0, z);
    Vec3 tip_to_vertex = vec3_sub(pos, vertices->data[0].static_3d.position);
    Vec3 center_to_vertex = pos;
    Vec3 tangent = vec3_cross(VEC3_Y, center_to_vertex);
    Vec3 normal_dir = vec3_cross(tangent, tip_to_vertex);
    Vec3 normal = vec3_normalise(normal_dir);
    VERT_3D(vertices, pos, normal, vec2(0, 0));
  }
  for (u32 i = 1; i < resolution; i++) {
    push_triangle(indices, 0, i + 1, i);
  }
  push_triangle(indices, 0, 1, resolution);

  // base center
  u32 center_idx = vertices->len;
  VERT_3D(vertices, VEC3_ZERO, VEC3_NEG_Y, vec2(0, 0));

  // base circle
  for (u32 i = 0; i < resolution; i++) {
    f32 x = cos(step * i) * radius;
    f32 z = sin(step * i) * radius;
    VERT_3D(vertices, vec3(x, 0.0, z), VEC3_NEG_Z, vec2(0, 0));
  }
  for (u32 i = 1; i < resolution; i++) {
    push_triangle(indices, center_idx, center_idx + i, center_idx + i + 1);
  }
  push_triangle(indices, center_idx, center_idx + resolution, center_idx + 1);

  Geometry geo = {
    .format = VERTEX_STATIC_3D,
    .vertices = vertices,
    .has_indices = true,
    .index_count = indices->len,
    .indices = indices,
  };
  return geo;
}

Geometry Geo_CreateCylinder(f32 radius, f32 height, u32 resolution) {
  Vertex_darray* vertices = Vertex_darray_new(1);
  u32_darray* indices = u32_darray_new(1);

  f32 step = TAU / resolution;

  // bot cap
  VERT_3D(vertices, VEC3_ZERO, VEC3_NEG_Y, vec2(0, 0));
  for (u32 i = 0; i < resolution; i++) {
      VERT_3D(vertices, vec3(cos(step * i) * radius, 0.0, sin(step * i) * radius), VEC3_NEG_Y, vec2(0, 0));
  }
  for (u32 i = 1; i < resolution; i++) {
    push_triangle(indices, 0, i, i + 1);
  }
  push_triangle(indices, 0, resolution, 1);

  // top cap
  u32 center_idx = vertices->len;
  VERT_3D(vertices, vec3(0.0, height, 0.0), VEC3_Y, vec2(0, 0));
  for (u32 i = 0; i < resolution; i++) {
    VERT_3D(vertices, vec3(cos(step * i) * radius, height, sin(step * i) * radius), VEC3_Y,
            vec2(0, 0));
  }
  for (u32 i = 1; i < resolution; i++) {
    push_triangle(indices, center_idx, center_idx + i + 1, center_idx + i);
  }
  push_triangle(indices, center_idx, center_idx + 1, center_idx + resolution);

  // sides
  u32 sides_start = vertices->len;
  for (u32 i = 0; i < resolution; i++) {
    f32 x = cos(step * i) * radius;
    f32 z = sin(step * i) * radius;
    // top then bottom
    VERT_3D(vertices, vec3(x, height, z), vec3_normalise(vec3(x, 0.0, z)), vec2(0, 0));
    VERT_3D(vertices, vec3(x, 0.0, z), vec3_normalise(vec3(x, 0.0, z)), vec2(0, 0));
  }
  for (u32 i = 0; i < resolution; i++) {
      u32 current = sides_start + i * 2;
      u32 next = sides_start + ((i + 1) % resolution) * 2;
      push_triangle(indices, current, next, current + 1);
      push_triangle(indices, current + 1, next, next + 1);
  }

  Geometry geo = {
    .format = VERTEX_STATIC_3D,
    .vertices = vertices,
    .has_indices = true,
    .index_count = indices->len,
    .indices = indices,
  };
  return geo;
}