tgx::Meshlet3Dv2 Struct Reference

Header for a single meshlet inside a Mesh3Dv2 object. More...

#include <Mesh3Dv2.h>

Public Attributes
int16_t	sphere_center [3]
	Quantized bounding sphere center relative to the global bounding-box center.
int16_t	cone_dir [3]
	Signed-normalized quantized visibility cone direction.
uint16_t	sphere_radius
	Quantized bounding sphere radius.
int16_t	cone_cos
	Signed-normalized cone cosine. Values <= -32767 disable meshlet cone culling.
uint32_t	payload_offset32
	Offset of this meshlet payload in Mesh3Dv2::payload, in 32-bit words.
uint8_t	nb_vertices
	Number of local vertices. With the uint8_t face stream format, this must be <= 128.
uint8_t	nb_normals
	Number of local normals.
uint8_t	nb_texcoords
	Number of local texture coordinates.
uint8_t	material_index
	Index in Mesh3Dv2::materials.

Detailed Description

Header for a single meshlet inside a Mesh3Dv2 object.

Meshlet headers are stored in a compact linear array and are read before touching the meshlet payload. This makes it possible to reject invisible meshlets quickly using the bounding sphere and visibility cone.

The sphere and cone metadata are quantized relative to the mesh global bounding box. The renderer reconstructs this metadata before it touches the meshlet payload:

bbox_center = 0.5 * (mesh.bounding_box.min + mesh.bounding_box.max)
bbox_extent = max(mesh.bounding_box size on x/y/z)
 
decoded_sphere_center = bbox_center + sphere_center[i] * (bbox_extent / 65534)
decoded_sphere_radius = sphere_radius * (bbox_extent / 65535)
decoded_cone_dir      = cone_dir[i] * (1 / 32767)
decoded_cone_cos      = cone_cos * (1 / 32767)

A cone_cos value below or equal to -1 disables meshlet cone culling. The payload offset is expressed in 32-bit words into Mesh3Dv2::payload. This guarantees that every meshlet payload starts on a 4-byte boundary when Mesh3Dv2::payload points to a uint32_t array. The payload generator must also pad each meshlet payload to a multiple of 4 bytes.

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The documentation for this struct was generated from the following file:

• src/Mesh3Dv2.h