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BTG file format: Difference between revisions
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Added description of vertex and normal list
RalfGerlich (talk | contribs) (Initial version) |
RalfGerlich (talk | contribs) (Added description of vertex and normal list) |
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| Line 146: | Line 146: | ||
| Index Types | | Index Types | ||
|} | |} | ||
Similarily, each element starts with a single unsigned integer, giving the number of bytes the element's data occupies. | |||
=== Bounding Sphere Object === | === Bounding Sphere Object === | ||
The Bounding Sphere object gives the bounding sphere of the tile, defined by a center and a radius. | The Bounding Sphere object gives the bounding sphere of the tile, defined by a center and a radius. | ||
The properties of a Bounding Sphere are ignored. | |||
The elements of the Bounding Sphere object are bounding spheres. | The elements of the Bounding Sphere object are bounding spheres. | ||
| Line 161: | Line 165: | ||
|- | |- | ||
| align="right"| 0 | | align="right"| 0 | ||
| unsigned int | |||
| number of bytes in this element | |||
|- | |||
| align="right"| 4 | |||
| double | | double | ||
| | | x-part of the center | ||
|- | |- | ||
| align="right"| | | align="right"| 12 | ||
| double | | double | ||
| y-part of the center | | y-part of the center | ||
|- | |- | ||
| align="right"| | | align="right"| 20 | ||
| double | | double | ||
| z-part of the center | | z-part of the center | ||
|- | |- | ||
| align="right"| | | align="right"| 28 | ||
| float | | float | ||
| radius of the bounding sphere | | radius of the bounding sphere | ||
|} | |} | ||
Note that the element may be longer than 32 bytes, but only the first 32 bytes are actually used. | |||
=== Vertex List === | === Vertex List === | ||
The Vertex List object contains a list of vertices to be referenced by other geometry primitives. | |||
The properties of a Vertex List object are ignored. | |||
Each element of a Vertex List object is a list of vertices. | |||
Each of the vertices gets a unique index, starting with 0 for the first vertex found in the file and incrementing by 1 for each further vertex. | |||
{| border="1" | |||
|- | |||
! Byte offset | |||
! Type | |||
! Description | |||
|- | |||
| align="right"| 0 | |||
| unsigned int | |||
| number of bytes in this element | |||
|- | |||
| align="right"| 4 | |||
| vertices | |||
| vertex list | |||
|} | |||
Each vertex is a triple of single precision floating point values: | |||
{| border="1" | |||
|- | |||
! Byte offset | |||
! Type | |||
! Description | |||
|- | |||
| align="right"| 0 | |||
| float | |||
| x-part of the vertex coordinates | |||
|- | |||
| align="right"| 4 | |||
| float | |||
| y-part of the vertex coordinates | |||
|- | |||
| align="right"| 8 | |||
| float | |||
| z-part of the vertex coordinates | |||
|} | |||
The number of vertices in an element is therefore the number of bytes in the element divided by 12. | |||
=== Normal List === | === Normal List === | ||
The Normal List contains a list of normals to be referenced by other geometry primitives. | |||
The properties of a Normal List object are ignored. | |||
Each element of a Normal List object is a list of normals. | |||
Each of the normals gets a unique index, starting with 0 for the first normal found in the file and incrementing by 1 for each further normal. | |||
{| border="1" | |||
|- | |||
! Byte offset | |||
! Type | |||
! Description | |||
|- | |||
| align="right"| 0 | |||
| unsigned int | |||
| number of bytes in this element | |||
|- | |||
| align="right"| 4 | |||
| normals | |||
| normal list | |||
|} | |||
Each normal is a triple of signed bytes, interpreted as fixed point values: | |||
{| border="1" | |||
|- | |||
! Byte offset | |||
! Type | |||
! Description | |||
|- | |||
| align="right"| 0 | |||
| byte | |||
| x-part of the normal coordinates | |||
|- | |||
| align="right"| 1 | |||
| byte | |||
| y-part of the normal coordinates | |||
|- | |||
| align="right"| 2 | |||
| byte | |||
| z-part of the normal coordinates | |||
|} | |||
The individual parts are interpreted by dividing each of the parts by 127.5 and subtracting 1.0, leading to a linear mapping from the range of 0...255 to the range of -1.0...1.0. | |||
=== Texture Coordinates List === | === Texture Coordinates List === | ||