[x3d-public] Extensions from Castle Game Engine that could be generally useful in the X3D standard

[Michalis Kamburelis]

Hi,

Following the today's discussion on X3D WG Meeting, here are some
extensions from Castle Game Engine that you may consider:

1. Smaller extensions:

  1.1. X3DShapeNode.shading = "DEFAULT"|"PHONG"|"WIREFRAME|..." field.
See https://castle-engine.sourceforge.io/x3d_extensions.php#section_ext_shading

  1.2. Allow to use TextureCoordinateGenerator on primitives, by a new
field: Box/Cone/Cylinder/Sphere/Extrusion/Text.texCoord . This is also
useful for other texture-generating nodes (like two existing proposals
for projective-texturing). See
https://castle-engine.sourceforge.io/x3d_implementation_texturing_extensions.php#section_ext_tex_coord

  1.3. Generating 3D texture coordinates in world space:
TextureCoordinateGenerator.mode =
["WORLDSPACEREFLECTIONVECTOR","WORLDSPACENORMAL"]. These modes allow
using GeneratedCubeMapTexture as a simple mirror. See
https://castle-engine.sourceforge.io/x3d_implementation_texturing_extensions.php#section_ext_tex_coord_worldspace
, https://castle-engine.sourceforge.io/x3d_implementation_cubemaptexturing.php

  1.4. Generating texture coordinates based on the shape's bounding
box: TextureCoordinateGenerator.mode =
["BOUNDS","BOUNDS2D","BOUNDS3D"]. These allow to explicitly request a
kind of coordinate generation that is right now available by default
in some situations. Very useful when transforming X3D graph. See
https://castle-engine.sourceforge.io/x3d_implementation_texturing_extensions.php#section_ext_tex_coord_bounds

  1.5. Specify whether texture alpha should be used for alpha testing
or alpha blending: alphaChannel=["AUTO"|"NONE"|"TEST"|"BLENDING"]. See
https://castle-engine.sourceforge.io/x3d_implementation_texturing_extensions.php#section_ext_alpha_channel_detection

  1.6. Specify blending factors: BlendMode node. This is an Instant
Reality extension,
http://doc.instantreality.org/documentation/nodetype/BlendMode/ ,
implemented in a compatible way in CGE:
https://castle-engine.sourceforge.io/x3d_extensions.php#section_ext_blending

2. Some larger extensions, that will understandably need discussion
and more input from other implementors:

  2.1. Compositing shaders extensions that we talked about today,
https://castle-engine.sourceforge.io/compositing_shaders.php

  2.2. Screen effects using shaders,
https://castle-engine.sourceforge.io/x3d_extensions_screen_effects.php

  2.3. Some way to make shadows, see
https://castle-engine.sourceforge.io/x3d_extensions_shadow_maps.php ,
https://castle-engine.sourceforge.io/x3d_extensions_shadow_volumes.php
. But I would start "cautiously" here, and include in the X3D
specification something much simpler than my own extensions. See my
mail "X3D features missing, but desired, by a game engine" that I'll
send shortly to the same address:)

  2.4. Some way to pass camera information to shaders. I have my
extensions for this:
https://castle-engine.sourceforge.io/x3d_implementation_navigation_extensions.php#section_ext_viewpoint_camera_matrix
. But I'm not happy with my own work here, connecting these events
from a Viewpoint node proved uncomfortable when you have many
viewpoints in a scene. I would like to redesign it using something
like a ViewpointSensor node.

3. Note: I did *not* mention on the list above my bump mapping
extensions ( https://castle-engine.sourceforge.io/x3d_implementation_texturing_extensions.php#section_ext_bump_mapping
). That is because I would prefer to see CommonSurfaceShader (from
Instant Reality) to be included in the X3D specification. It also
allows bump mapping, and many other features.

Best regards,
Michalis