Extended ShadowcasterUpdater and shaders to handle multiple shadowcaster planes by introducing indexed properties and logic for two shadowcaster sets. Updated property names and shader logic to support per-index shadowcaster textures, colors, and brightness, enabling more flexible shadow casting in scenes.
Introduces shadowcaster support by adding shadow map index fields to light data, updating PlayerPositionsToShader and LightdataStorage to handle shadow map indices, and extending the shader and its includes to sample shadowcaster planes. Adds ShadowcasterUpdater script and editor preview for updating world-to-local matrices, and updates relevant arrays and property handling throughout the codebase. Also adds a sample plane mesh for shadowcasting.
Updated all relevant shader files and C# script to use Udon-prefixed light and player variables (e.g., _Udon_LightPositions, _Udon_LightColors, _Udon_PlayerCount) for consistency and to avoid naming conflicts. This change affects variable declarations, macro definitions, and all usages in BlendinShader, LitParticles, Water shaders, and included HLSL files.
Changed shader property names to use '_Udon_' prefix and switched to using VRCShader.PropertyToID and VRCShader.SetGlobal* methods for setting shader properties. Added update throttling in LateUpdate for performance. These changes improve compatibility and efficiency with the VRC SDK3 Rendering API.
