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Interactive paper companion

See what a splat measures.

Explore the renderer and the geometric part of the tracker using small synthetic scenes.

LAB 01Spherical rendering

Change the front splat

Try this Lower opacity and click the range image. The rear splat contributes more to each ray.

3D planes, one selected ray

exact intersections
A · adjustableB · rearC · side

Spherical range image

0 mClick to inspect a ray12 m
Dacc = ∑ w d—
E[d | hit] = D / O—
Opacity O = ∑ w—
Selected ray's hits sorted front to back
Hit orderRange dα = oGWeight w

wᵢ = αᵢ ∏ⱼ₍ⱼ<ᵢ₎ (1 − αⱼ). Dacc is unnormalised; D/O is undefined without a hit.

Set an initial pose

Align the scan to surfaces

SE(2) analogue
MapTransformed scanInitial scan
Ready · press Run or Step.

Does a low residual mean a good pose?

Residual RMSEPosition error*
Residual—
Position error*—
Yaw error*—
Corner geometry constrains the pose. Surfaces with different normals resolve both translations and yaw.

rᵢ = nᵢᵀ(Rqᵢ + t − pᵢ). Robust Gauss–Newton recomputes matches each step. *Truth is used only to evaluate error.

How to explore

Rendering: rotate and resize the front Gaussian, lower its opacity, then select a ray in the image. Compare each intersection's range, opacity, and front-to-back weight. Switch between accumulated range, opacity-normalised expected range, and opacity.

Registration: run the room-corner case, then switch to a corridor. The geometric residual can become very small while motion along the corridor remains unobservable. Increase the synthetic noise along surface normals to see an actual residual floor.

Scope: this is an explanatory simulation. It uses three planar 3D Gaussians and per-ray sorting, not the paper's GPU tile rasteriser. Its registration lab implements only the geometric point-to-line SE(2) analogue. Splat-LOAM uses SE(3), rendered-keyframe geometry, and a joint geometric plus range-image warping objective; Gaussian map optimisation is a separate operation. The repository's optional median-depth mixture is omitted.

Paper: §§3.2, 3.3.3 · Reference implementation