wip: uvsphere mesh gen and pbr shader first pass

1 files changed, 61 insertions, 3 deletions

diff --git a/src/maths/primitives.c b/src/maths/primitives.c
index c0af140..3931b93 100644
--- a/src/maths/primitives.c
+++ b/src/maths/primitives.c
@@ -112,7 +112,7 @@ geometry_data geo_create_cuboid(f32x3 extents) {
     .vertices = vertices,
     .has_indices = true,
     .indices = indices,  // FIXME: make darray methods that return stack allocated struct
-    .colour = vec3(0, 0, 0),
+    .colour = (rgba){ 0, 0, 0, 1 }
   };
 
   return geo;
@@ -133,6 +133,64 @@ geometry_data geo_create_cuboid(f32x3 extents) {
 
 // --- Spheres
 
-geometry_data geo_create_uvsphere(f32 radius, f32 north_south_lines, f32 east_west_lines) {
-  // TODO
+vec3 spherical_to_cartesian_coords(f32 rho, f32 theta, f32 phi) {
+  f32 x = rho * sin(phi) * cos(theta);
+  f32 y = rho * sin(phi) * sin(theta);
+  f32 z = rho * cos(phi);
+  return vec3(x, y, z);
+}
+
+geometry_data geo_create_uvsphere(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, 0, radius),
+                                .normal = vec3(0, 0, radius),
+                                .tex_coords = vec2(0, 0) } };
+
+  // parallels
+  for (u32 i = 0; i < (east_west_lines - 1); i++) {
+    // phi should range from 0 to pi
+    f32 phi = PI * ((i + 1) / east_west_lines);
+
+    // meridians
+    for (u32 j = 0; j < east_west_lines; j++) {
+      // theta should range from 0 to 2PI
+      f32 theta = TAU * (j / north_south_lines);
+      vec3 position = spherical_to_cartesian_coords(radius, theta, phi);
+      f32 d = vec3_len(position);
+      assert(d == radius);  // all points on the sphere should be 'radius' away from the origin
+      vertex v = { .static_3d = {
+                       .position = position,
+                       .normal = 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, 0, -radius),
+                                .normal = vec3(0, 0, -radius),
+                                .tex_coords = vec2(0, 0) } };
+
+  // TODO: generate indices for for each flat quad on the UV sphere and triangles
+  //       where they meet the north and south poles
+  u32_darray* indices = u32_darray_new(1);
+
+  geometry_data geo = {
+    .format = VERTEX_STATIC_3D,
+    .vertices = vertices,
+    .has_indices = true,
+    .indices = indices,
+    .colour = RED_800,
+  };
+  return geo;
 }