triplanar

Triplanar mapping is a texture projection technique used in computer graphics to texture 3D geometry without relying on explicit UV coordinates. It projects textures from three orthogonal directions along the x, y, and z axes and blends the results based on the surface normal. This approach helps reduce texture stretching and visible seams on complex or deforming meshes, such as terrain, voxel models, or sculpted surfaces.

In a typical shader-based implementation, the world-space position P and normal N are used to determine blending weights. The weights are derived from the absolute values of the normal’s components: wX = |Nx|, wY = |Ny|, wZ = |Nz|, and are then normalized so that wX + wY + wZ = 1. Each projection samples a texture along a plane perpendicular to one axis: texX is sampled using the YZ coordinates of P, texY from the XZ plane using P.x and P.z, and texZ from the XY plane using P.x and P.y. The final color or material value is a weighted blend: color = wX * texX + wY * texY + wZ * texZ. Texture tiling scales are adjustable to control detail and repeat patterns, and the same approach can be extended to normal maps and other material maps.

Benefits of triplanar mapping include avoidance of UV unwrapping, resilience to distortion on irregular geometry, and straightforward integration into shading pipelines. It is widely used for terrain surfaces and procedurally generated models. Limitations include higher texture fetch costs, potential blur or seams if texture scales are not well matched to geometry, and the need to manage tiling and normals across axes to maintain consistent shading.