Additional notes added to caster docs.

This needs to be cleaned up further.

src/batgrl/gadgets/_raycasting.pyx

@@ -371,6 +371,8 @@ def cast_rays(
 
 
 cdef uint8 shade_wall(uint8 value, double distance):
+    # ! Should shading be set by kwarg in caster?
+    # ! `-0.15` is pretty arbitrary.
     return <uint8>(value * exp(-0.15 * distance))
 
 
@@ -507,6 +509,7 @@ def text_cast_rays(
                 continue
 
             tex_pos += step
+            # ! How much to shade a side wall? `2.0 * side` for now...
             wall_value = shade_wall(
                 wall_texture[tex_y, tex_x], perp_wall_dist + 2.0 * side
             )

src/batgrl/gadgets/raycaster.py

@@ -14,6 +14,15 @@ class Raycaster(Graphics):
     r"""
     A raycaster gadget.
 
+    ``caster_map`` should not contain a value greater than the length of
+    ``wall_textures``. A non-zero value ``N`` in ``caster_map`` represents a wall with
+    texture ``wall_textures[N - 1]``.
+
+    ``sprite_indexes`` should not contain a value greater than or equal to the length of
+    ``sprite_textures``. A value ``N`` in ``sprite_indexes`` represents a sprite with
+    texture ``sprite_textures[N]``. ``sprite_coords`` and ``sprite_indexes`` must be the
+    same length.
+
     Parameters
     ----------
     caster_map : NDArray[np.uint8]

src/batgrl/gadgets/text_raycaster.py

@@ -12,7 +12,23 @@
 
 class TextRaycaster(Text):
     r"""
-    A raycaster gadget.
+    A raycaster gadget that renders with text.
+
+    ``caster_map`` should not contain a value greater than the length of
+    ``wall_textures``. A non-zero value ``N`` in ``caster_map`` represents a wall with
+    texture ``wall_textures[N - 1]``.
+
+    The integer arrays in ``wall_textures`` determine how walls are shaded. With low
+    values darker and high values lighter.
+
+    ``sprite_indexes`` should not contain a value greater than or equal to the length of
+    ``sprite_textures``. A value ``N`` in ``sprite_indexes`` represents a sprite with
+    texture ``sprite_textures[N]``. ``sprite_coords`` and ``sprite_indexes`` must be the
+    same length.
+
+    It's convention in ``batgrl`` to refer to RGBA arrays as textures. ``wall_textures``
+    and ``sprite_textures`` do not contain RGBA arrays, but the names are kept to be
+    consistent with the graphics raycaster.
 
     Parameters
     ----------