Add a parallax terrain example, and tighten the occlusion march limit - #9223
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New `materials/parallax-terrain` example: a cpu generated displaced grid with one ground material over all of it, so the marched mode is seen across a wide range of distances and viewing angles at once - which is where it earns its cost over the single tap one. A directional light with cascaded shadows and 40 trees give the relief something to be shadowed by, and the panel exposes the parallax mode, sample budget and height alongside the cascade and soft shadow settings. Also lowers `parallaxMaxSlope` from 10 to 5. It caps the ray at that multiple of the relief depth, which is what bounds how far the lookup slides along the surface at a grazing angle - and that slide is what makes the relief appear to swim as the camera moves, because the geometry never moves, only the texture lookup does. Measured on this terrain, the slide varied by 0.26 world units over a small camera move at 10, 0.17 at 3 and 0.03 at 1.5, against a relief only 0.25 deep. 5 keeps grazing relief without the visible swim. This is a visible change for any material using PARALLAX_OCCLUSION: less relief at extreme grazing angles, in exchange for a stable image. Textures are ambientCG Ground092C, CC0, 1K converted to webp (0.7MB against 3.3MB for the equivalent jpg maps). Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Build size reportThis PR changes the size of the minified bundles.
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Feels like there is a height fade out based on fragment distance is required, to fade into no-parallax based on proximity. |
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Both number of taps for parallax and number of taps for shadows fade out based on pixel size .. so in the distance the parallax is cheaper all the way to disabled. See this https://x.com/ValigurskyM/status/2091916601293496351 |
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New example:
materials/parallax-terrainA cpu generated displaced grid with a single ground material over all of it, so the marched parallax mode is seen across a wide range of distances and viewing angles at once - the case it earns its cost in over the single tap one. A directional light with cascaded shadows and 40 trees give the relief something to be shadowed by, and the camera is the hybrid
CameraControls(orbit + fly) so the whole terrain can be visited.Controls: parallax Mode / Samples / Height, Shadow Cascades (filtering, count) and Soft Shadows (falloff, samples, blocker samples).
Textures are ambientCG Ground092C, CC0, 1K converted to webp - 0.7 MB against 3.3 MB for the equivalent jpg maps. The tree model is the existing
low-poly-tree.glb, credited in the example header.Behaviour change:
parallaxMaxSlope10 → 5PARALLAX_OCCLUSION.The constant caps the march at that multiple of the relief depth, which bounds how far the lookup slides along the surface at a grazing angle. That slide is what makes the relief appear to swim as the camera moves: parallax fakes depth by displacing the texture lookup by
depth × tan(θ)while the pixel itself never moves, andd(tan θ)/dθ = sec²θis ~13 at 74° off the normal, so a small camera move slides the texture a long way.Measured on this terrain, on a slope at ~74°, with the relief only 0.25 world units deep:
parallaxMaxSlope5 was picked by eye as the point where grazing relief still reads without the visible swim. The trade is less apparent depth at extreme grazing angles in exchange for a stable image. Ruled out as causes by measurement, for the record: the distance fade (forcing it to 1 changed the result by 0.0001), the explicit mip level (lod 0 vs +2 moves the depth ~7%), and mesh tessellation (nothing in the march depends on triangle density).
Verified on WebGL2 and WebGPU, all five shadow filtering modes and cascade counts 1-4.